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WIGGLING 'LITE' IN GUEST MODE

Buchla 208r V2.1 (Blue) Build Thread
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author Buchla 208r V2.1 (Blue) Build Thread
Don T
Roman's newest version of the 208r contains quite a few changes, and many mistakes from the older versions have been corrected, so I think it may be worth starting a new build thread for this version. Due to the many corrections, there will/should be less modifications and other tweaks made, and this should hopefully turn out to be a much shorter thread.

To get the ball rolling, here goes:

First, if your boards look like this, you indeed have a 208r V2.1:



Here's the link to the updated BOM and parts layout diagrams:

Stored-Program-Sound-Source-Model-208r V2.1

The first thing to note: I at first thought that the missing trace from Pin 5 of Card 1 to Pin 7 of the programming card slot had been added. This is not the case, the trace is still missing. The correction that sduck posted in the previous thread will still need to be made:



The first notable correction is on Card 3, the Envelope Generator. Previously, two of the pins of the 2N2907A in the 13.5V supply had to be swapped, and a flying 100K load resistor had to be added to get the correct output voltage. This has been fixed, so insert the 2N2907A without crossing any legs:



And the formerly flying 100K resistor has a spot on the board, and it goes here (Be glad I didn't go with making this an animated .gif where the word "Here" blinked like I wanted to at first twisted ):



A couple other suggestions for further along in the build that may save some people some trouble (I'm a visual thinker, so have a few hopefully helpful pics):

Card 6 - Match the two 2N3565 transistors, Q2 and Q3, for Vbe. These two are the core of the Modulation Oscillator, which is basically 1/2 a Buchla 258 without the sine shaper circuit:



Card 8 - Match the components enclosed in the like-colored rectangles:



Match D1 and D2 (1N457) with the diode checker on your DMM, which should display a Voltage reading. R36 and R37 are 330K, and R38 and R39 are 680 Ohms. Even if using 1% resistors, I would still match the closest pairs I could. These components, along with Q1, are the sine shaper circuit from the Buchla 258. The better they match, the easier time you'll have getting a clean sine wave. Also, Q1 is a 2N4339 that should have an Idss between .7 and 1.2mA.

[EDIT]: In case people need these for chasing bugs, attached are the schematics for the version of the 208 that Roman's boards are based upon. The schematics on Magnus' most awesome site are for a later version of the 208.

[EDIT - February 1, 2017]: Even more help for bug-chasing: I cannot remember where online I found this, but I'm attaching a pdf file that shows the entire 208 Mother Board schematic as one continuous image. I've found it very helpful. If anyone knows who should get the credit for this image, let me know!

[EDIT - January 30, 2017]:
In case something goes wrong, here are a few general troubleshooting tips, plus a short example (presented at the risk of making even more a fool of myself)

If something doesn't work, or work as expected (Go through this list In Order!) -
1. Check the power supply Voltages!!!!
2. Go back and make sure you put all the parts in (more on this in a bit!) Good suggestion from Peake: Hold the (hopefully completed) board up to a bright light, and look for any unexpected holes.
2A. If you put your chips in sockets, make sure none of the pins got folded under and are not making contact
3. Double-check the board against the BOM and the parts placement pics to make sure you put the correct parts in the correct places, and with the correct polarity. This means all diodes, vactrols, chips, electrolytic and tantalum caps facing the correct direction. This is an easy mistake to make, so the more sure you are that you didn't make this mistake, the more you probably should make yourself double-check Mr. Green
4. Check all the solder joints on the card. It is easy to miss soldering a lead or two sometimes. An incomplete, broken, or bad solder joint can cause all sorts of problems. If in doubt, re-solder it, but don't be sloppy.
4A. Check for solder bridges between component pins that are not meant to be connected, or between adjacent traces that are not supposed to touch. This can happen easily if too much solder is applied to a connector, or a chip socket/chip. The photos of the boards on davebr's site are a wonderful reference if you're not sure a connection is bridged (Note that this is V2, not V2.1):

http://modularsynthesis.com/roman/buchla208v2/208spss.htm

5. Try swapping chips, assuming you put them in sockets.
6. If you didn't put the chips in sockets, or you suspect a permanently soldered-in component, get the DMM out and start checking for reference voltages against the voltages that are indicated on the schematics.
7. Ask for help!! Because if still no joy at this point, the problem could be complicated!

Here's a short story for you related to the above:
Finished up Card 2 (Random Voltage Generator) the other night. Went to test. Nothing, nada. I had recently checked the power supply, and everything else was working normally, so...
I skipped to Step Number 5 on the list above. Swapped one chip, tested, swapped another chip, tested, swapped another... until I had swapped them all out. Still nothing. So, after wasting all that time, I got marginally wiser (but not much), and skipped back up to Step Number 4. All the solder joints looked great, until I got to a place where there were two holes I wasn't expecting to see. I flipped the board over and:



Yes, that 1M resistor was still missing after everything else was installed and I thought the card was complete. So, no matter your level of experience (and believe me, I'm still no expert), go through the general troubleshooting list In. The. Order. Above. There's a reason Step Number 2 is Step Number 2.

After adding that one missing resistor, and kicking myself a few times, the Random Voltage Generator worked as expected!
Don T
Just moving this bit of information from the other thread for the benefit of those who are looking into buying vactrols for this build:

Don T wrote:
muncky wrote:
- now fretting about excelitas b xvive, but other than very excited...!


I'll offer my observations and opinion on this, and it's only my opinion, and based on a small sample, but here goes:

I built a Card 10 for the 208 (Gate 1) that had the vactrols socketed. I tested Excelitas VTL5C3, Xvive 5C3, and Xvive 5C1. With the attack, duration, and decay sliders all the way up, here's how they compared: The Excelitas 5C3 was as we would all expect, while the Xvive 5C3 had a barely perceptibly slower attack than the Excelitas, but the decay was much longer, and it took what I thought was an unacceptable length of time to finally settle at the bottom of its curve. If it wasn't for the long tail at the bottom of the curve, the difference would not have been so pronounced. As it is, fast, short notes repeated rapidly would start bleeding together long before the triggers reached audio rate with the Xvive 5C3.

The Xvive 5C1 was an entirely different beast. It is fast. Very fast, on both attack and decay. Compared to the Excelitas 5C3, it was basically almost too fast. Adding just a little duration and decay slider got the same response you would expect from the Excelitas 5C3.

The good news is that between the three, I noticed no real difference in tone on sustained sounds. And for those that don't know me, I make my living dealing with issues of tone quality.

The bottom line: If it was me building a 208 (And I'm just starting another one right now), I would go about vactrol preferences in this manner, in order of preference starting from the top:

1. Complete the build with Excelitas VTL5C3 in all positions.
2. Complete the build with Excelitas VTL5C3 in the balanced modulator and both Lopass Gates, with Xvive 5C1 in all other positions.
3. Complete the build with Excelitas VTL5C3 in both Lopass Gates, Xvive 5C1 in all other positions (This actually may improve the balanced modulator, but perhaps not as "authentic" as option 2).
4. Complete the build with Xvive 5C1 in all positions.

Like I said, this is just my opinion and observation. I know a couple other wigglers have been playing around with this as well, and they may choose to add to this, or not.
muncky
Thanks so much for starting this thread - can wait to start building this, and this kind of info is super helpful thumbs up
Reality Checkpoint
I am seriously considering building this, so this is great. Need to source some UA726. Are they ridiculously expensive, and can they be bought from a reliable source?
Don T
Reality Checkpoint wrote:
I am seriously considering building this, so this is great. Need to source some UA726. Are they ridiculously expensive, and can they be bought from a reliable source?


IF (Big if, get it?) you can find a genuine uA726, they will probably set you back around $100 each. There are many fakes out there, especially on eBay from Asian sources, so beware.

Thankfully, a couple uA726 alternatives are out there. papz has a small uA726 replacement board which I believe is based on the expo converter from the Moog Prodigy, and jhulk has a uA726 replacement board in the prototype stage that is based on a different circuit that also uses a heater. I will be testing jhulk's board in this build (As soon as I get them etched). I also have developed a replacement that uses a matched transistor pair and tempco that is in the prototype stage. My boards replace Card 6 and Card 7 entirely. I have a pair built, and another wiggler has built a set and is testing them in his 208. Eventually, I'll be able to give pitch drift tests between a 208 with real uA726, my tempco boards, and jhulk's replacement.
Peake
I've got a working 258r V1 with sockets for the 726 I've been waiting to test jhulk's replacement...would be happy to do so. Thanks for the post and information Don T!
Reality Checkpoint
Many thanks for that Don T, most helpful

I reckon that this build will expend my complete SDIY budget for the year so I must weigh that carefully against other projects that might come up. I shall follow this thread very carefully.
jhulk
mike if you want the foil files for self etch i can send you them thats what don t has

was waiting for final tests before doing a run or you can wait for the production run.
Peake
jhulk wrote:
mike if you want the foil files for self etch i can send you them thats what don t has

was waiting for final tests before doing a run or you can wait for the production run.


Drop them on my email please, I have a double-sided etch coming up and I'll add it in. With something that tiny I might not pull it off. I've done okay on a couple of 258R V2 builds using the 857 and 847 but they're at the limits of my soldering ability without something like a microscope! Thanks!
jhulk
they are soic and through hole parts 2 soic chips which are the largest of the smd types

don t is sending them you
jhulk
here is the size the picture of it



gives you an idea of the size of it its nearly 1" square
Peake
Oh, this is very different from what I'd seen before. Thanks to you and to Don!
davebr
My notes also say there was a missing run between Card3 pin 15 and Card4 pin 10. Also Trimmer TR3 on the motherboard should connect to pin 12 of Card8, not pin 11. This was on an early version and I have not kept track of revisions. Can you verify these on the blue?

Dave
Don T
davebr wrote:
My notes also say there was a missing run between Card3 pin 15 and Card4 pin 10.


I haven't started on the motherboard yet, so this was easy to check. I get continuity between those two pins, so that issue has been corrected.

davebr wrote:

Also Trimmer TR3 on the motherboard should connect to pin 12 of Card8, not pin 11.


Alas, Pin 12 is not connected to anything. Pin 11 is still connected to the wiper of TR3.

Dave (or anyone else), if you think of anything else to check while my motherboard is still blank, please let me know. I also emailed you a decoupling cap question related to this project in case you didn't see it.
Don T
This is not exactly a requirement, but is strongly suggested for long-term reliability, and can apply to other similar circuit boards.

For double-sided circuit boards that do not have a solder mask, i.e., the traces are not insulated, when installing resistors it is suggested to mount the resistor slightly above the board if one of the end caps would come into contact with an uninsulated trace. For example:



In the photo above, all three of the visible resistors would have their end cap area contacting a trace if they were pulled flush against the board. Yes, the resistor has a very thin insulating coating in that area, but over time that coating could flake off due to vibration, corrosion, or expansion/contraction due to heating/cooling cycles.

As I said, this is strictly not necessary, but anyone who has ever repaired a beast known as the "Polymoog" would probably back me up on this...

Carry on! cool

[EDIT]: Just for clarification, all those words above boil down to: Keep the body of the resistor above the board if the body is going to be contacting a trace. I get too wordy sometimes.
davebr
Don T wrote:
This is not exactly a requirement, but is strongly suggested for long-term reliability, and can apply to other similar circuit boards.

For double-sided circuit boards that do not have a solder mask, i.e., the traces are not insulated, when installing resistors it is suggested to mount the resistor slightly above the board if one of the end caps would come into contact with an uninsulated trace.

Another option is to use a "christmas tree" to bend the leads of all components. That way the bends are 90 degree and have clearance to neighboring PCB traces. The 208 is one of the few boards that actually uses a 0.400" resistor lead spacing so I can use my vintage "christmas tree". It's 40+ years old so has fewer standard spacings than this one at Sparkfun

Mine looks like just the bottom half of this one Thinkiverse

Good tip, though about shorting to runs. That is why even with solder mask I make sure all my component leads are perpendicular to the PCB. I never solder leads bent over.

Dave
Don T
Troubleshooting timesavers-

Tip 1 -
Should anyone encounter the following symptoms all at once:

1. Sequencer LEDs do not light.
2. LPG LEDs do not light.
3. CO Sine Wave is inaudible.

Your 208 is not getting +5V from your power supply. (Do NOT ask how I know this very frustrating )

A 208r V2 or V2.1 will work 95% correctly with NO +5V power present (Again, do NOT ask how I know this angry )

Tip 2 -
If your CO Sine Wave is audible, and both LPG LEDs work, but the Sequencer LEDs do not light, try replacing IC9 on Card 1, a CD4009
Don T
Some progress, and perhaps a solution to a common problem should anyone else want to confirm.

I have worked on many different pieces of gear, and have noticed almost all of them that use CMOS chips have a decoupling cap across the Vdd and Vss (or ground) pins of most, if not all the CMOS chips. The original 208, as well as the 208r V2 and V2.1, have NONE. Most of the stability issues in the 208r are CMOS-chip-related, and I happened to run across a deal on these really nice machined-pin sockets that have decoupling caps built-in. I figured it may be worth a try, and at the very least it should do no harm...

Since I'm not an expert (at all) on CMOS-related things, I ran the idea by davebr. He gave me a thorough and educational response (Dave, feel free to jump in, or I can share your response here if you'd like) that basically said it may be a good idea in the sequencer, but perhaps putting them on every CMOS chip would be overkill. He mentioned that he tends to put one decoupling cap for every three CMOS chips. Dave also cautioned to make sure that any additional caps would not add enough capacitance to allow a charge to be stored in a voltage regulated circuit large enough that it would reverse-bias a voltage regulator, unless the regulator has protection diodes installed. Think of it as a "back flow" if you will, especially when powering down.

So, with basically a "go for it", I installed the sockets on my sequencer board. The decoupling cap can be removed without too much trouble, so I pulled it out of the socket for the LM3900:



In my previous post, I mentioned the trouble I had been having with my first 208's sequencer LEDs, and the solution, which involved replacing what I assumed was a faulty CD4009, which is the LED driver for this circuit. As an experiment, I placed the new 4009 in one of those decoupled sockets to see if there would be a result, plus you can see above that I didn't use sockets at all on my first build, which tends to slow things down a bit if you need to replace a chip...

Here's that part you've been waiting patiently for, hoping I would shut up and just get on with it:

Before installing the decoupling socket, my first sequencer card displayed the common behavior of only doing 2 steps with the Stages switch set to 3. It would do 4 and 5 steps normally, but not 3. Well, after installing that socket with the decoupling cap, and no other modifications done, that same sequencer card now reliably switches between 3, 4, and 5 stages as designed! nanners

The new, blue sequencer card, which you can see above has decoupling caps everywhere except the LM3900, and no other modifications, also switches reliably between 3, 4, and 5 steps as designed.

Being a firm believer in "Correlation Does Not Imply Causality" (unless confirmed), I am not going to declare the decoupling solution as the fix for the 2, 4, 5 step sequencer bug until someone else confirms. All one needs to do is solder a 0.1uf cap (ceramic will do nicely) on the back of IC9 on their sequencer (Card 1) between pins 8 and 16. Please share your results here!

Right now, all I'm going to tell you guys is that I have two otherwise-unmodified sequencers that behave as intended!



And yes, the sockets just happened to be blue! nanners
Peake
Don T wrote:
Alas, Pin 12 is not connected to anything. Pin 11 is still connected to the wiper of TR3.


Anyone have a visual on what to cut and what to jump to solve for this please?
davebr
Peake wrote:
Don T wrote:
Alas, Pin 12 is not connected to anything. Pin 11 is still connected to the wiper of TR3.


Anyone have a visual on what to cut and what to jump to solve for this please?

This is on Card 8. Pin 11 is not used, so the easiest solution is simply to jumper pin 11 to pin 12. I do show that on card 8 on my 208 V2 Stored Program Sound Source Module page.

Dave
Don T
[EDIT]: Text deleted because davebr beat me to the answer cool
Peake
It can be done on card 8 and not the motherboard? Good news, thank you both! This -is- my first 208 build so thanks for the patience. I have your page open in my browser, Dave. Superb work.
Don T
Just to clarify, the recently found error on Card 2 that applies to some older versions of the 208r V2 does not apply to this version, which is correct.

Carry on...

davebr
Don T wrote:
Just to clarify, the recently found error on Card 2 that applies to some older versions of the 208r V2 does not apply to this version, which is correct.

Carry on...

Ah ... what recently found issue on card 2? I am currently building an older version so am interested ...

Dave
thereminsynth1234
Thanks for the post on this build I just started getting parts for the 2.1. I'll try to post some pics on progress. thumbs up Guinness ftw!
Don T
davebr wrote:
Don T wrote:
Just to clarify, the recently found error on Card 2 that applies to some older versions of the 208r V2 does not apply to this version, which is correct.

Carry on...

Ah ... what recently found issue on card 2? I am currently building an older version so am interested ...

Dave


Dave, instead of Pin 10 of IC4 being connected to the left lead of R31 as shown in the photo above, it is connected to the left lead of R23:



From my other post on this: "This mistake cuts a 1M resistor out of the feedback loop of an opamp, and connects that same opamp's output directly to the +15V rail!

Solution: You must cut the trace going to the left pin of R23, and jumper the trace coming from Pin 10 of IC4 (The one you just cut), and jumper that to the left pin of R31."

If you look closely at the photo of Card 2 you posted on your site of your previous V2 build, that card displays this error.

According to the schematic, the affected area is designed to prevent a "0" on startup in the random circuit
Peake
Uncertain regarding the wiring of the Preamp input interrupting jack; is this a from PCB to jack back to PCB signal path, in that it's normal'd until interrupted by an external input? Ground is given via the front panel? No ground required, just coax cable, no shield? Dang. No clear pics on any of the build pages. Edit: Finally found Roman's note on his build page, why didn't anyone tell me that's where it was?

Nearing the end of my blue PCB build; sequencer, pulser and envelope are all happily firing. Will still install the recommended 0.1uF cap on the seq PCB as found by Don.
Don T
Started on Card 5 today, the balanced modulator, and noticed a nice, but subtle change that is very helpful:

On Card 5, as well as the other cards that require vactrols to be installed on end with the photocell down, there is now a small pad added that indicates the hole where the positive (+) lead of the vactrol's LED should be inserted. A time and confusion saver no doubt!:





Thanks Roman!
Don T
A quick note, more for ease than necessity:

When building Card 5, stuff R22 (1.5K) about 3mm or so above the board. This will make it easier to bend it away from VTL1, allowing clearance for the + LED lead. Otherwise, R22 almost covers the hole. See below, R22 has been installed as suggested:

sempervirent
Thanks for this thread. I wish all the 200r modules had good build threads (the "other" forum is kind of a ghost town compared to MW).

On projects that have PCB errors it can be intimidating to dive in. You don't know what you don't know, so to speak.

Actually, for someone who's more of a 200r expert than myself, it would be really helpful to start an "errata" thread that lists all the known issues with each project in one place.
Don T
Updated first post, added a .zip file of the correct schematics for this version of the 208.
Musicology of Dreams
Don T wrote:
Updated first post, added a .zip file of the correct schematics for this version of the 208.


Thanks Don for useful update with schematics thumbs up
Peake
My modulation oscillator was doing nothing but I tracked it down to a dead 2N3802 (Q4). Build with confidence, this board works fine! I'm having a mystery with the Timbre section but otherwise everything is just great, beautiful work by Roman and excellent documentation by Don T, DaveBr and others! applause

Edit: Vintage 2N3802 do not work at Q4. They work perfectly in Roman's 258 version 1 and 2 where LS352 are also specified. They're original parts in the 258, replaced by an AD part in the 208. This takes into account the vintage part having a different pinout.
Don T
For Q4 on Card 6, I like to use 2N3806. It is a very good substitute for 2N3802. The pinout for 2N3806 is no problem on Roman's boards. I believe davebr used/uses them in his builds as well.



No, that board is not blue. It doesn't have a uA726 either. It is a one-off prototype to test a matched NPN pair and tempco, but everything else is the same. It just happens to be a really good pic of a 2N3806 cool
Virusinstaller
Could we collate all this great information to a shared google doc?
To slowly build a verified build instruction.
roman_f
a small off-topic:
i have uploaded 218 REV2 mod instructions and HEX code
http://electricmusicstore.com/blogs/build/touch-activated-voltage-sour ce-model-218
Don T
Some card building hints, in case you've never built one of these before:

When fitting the Molex connectors, "tack solder" them in on just one pin each:



Then, look down the edge of the connectors and make sure they are all aligned in a perfectly straight line. If they need lining up, reheat the one pin holding that connector while holding the connector firmly flush to the board:



After all the connectors are In. A. Straight. Line., solder the rest of the pins. Be generous, but not sloppy, with the solder on these. Removing one of these type connectors is not easy, so don't skip this step!
Don T
Up for today, Card 5, the modulator card:



I decided to use only one decoupling cap, and will most likely continue the build with only one decoupling cap per card, none if there are no CMOS chips on board.

Make sure you are using the V2.1 BOM on this card, as it has been corrected to show that the zener diodes are 1N5236. This is the correct value, and the original schematics reflect this. I'm not even going to discuss what happens if you use the part number called for in the previous BOM, but here's a hint: Dead Banana

With this particular card, I tried something that I've wanted to do for a long time, and that was to use four VTL5C1 Vactrols in the Balanced Modulator section. I especially wanted to try it now because of my belief that if you are building with Xvive Vactrols, you should use 5C1 throughout, as opposed to their 5C3. I didn't use Xvive here though, as I had a small stash of NOS VTL5C1, most of which still have the Vactec label:



Luckily, the place I got these from had tested these, and had marked them with their on resistance, so I was able to go through the ones I had and find four that were closely matched.

So, does it sound different? Yes. I. Love. It. In fact, I'm tempted to go back into my other build and replace the Excelitas 5C3 Vactrols with these. I'm not sure how to accurately describe the difference in sound, but I'll try. The faster 5C1 Vactrols allow the ingoing signals to be passed more accurately, i.e., "cleaner", but "cleaner" does not imply "sterile" in this case. The resulting sound is much wilder! Is it as "authentic"? Maybe, maybe not. My first experience with a Ring Modulator was in college, with the ringmod in an ARP 2600. I fell in love with that sound. The 208's balanced modulator sounds a lot more like what I expect from a ring modulator with VTL5C1 installed. Perhaps if I get time soon, I'll make and post a couple of comparison videos.

At the very least, I recommend matching VT1, 2, 3, and 4 on Card 5, and I recommend VTL5C1 in their positions.
Don T
And now, Card 3:

(Sorry about skipping around, but it is what it is. Tomorrow I'm probably building Card 9 to help out a fellow wiggler who is having issues with their Timbre circuit)

Card 3 built up as expected, and worked flawlessly. One thing to note: Be patient with stuffing the resistors and double-check the parts placement photo against the BOM, there are a lot of "oddball" values on this card.

On the previous version of Card 3, it was necessary to twist 2 of the legs of the 2N2907A transistor around each other. As noted earlier in this thread, that is no longer an issue, so make sure it is installed the way it naturally fits:



WARNING for the unwary: I make it a practice to never mount a transistor with the bottom flush to the circuit board, unless specifically instructed to do so. In this particular case, the LED driver transistor, 2N1711, will naturally fall into place when you stuff it in the board, and there's nothing to hold it above the board. Make sure you install the 2N1711 with the body a couple millimeters above the board! If you do not, the bottom of the transistor's body will short a couple traces that travel underneath:

memes_33
roman_f wrote:
a small off-topic:
i have uploaded 218 REV2 mod instructions and HEX code
http://electricmusicstore.com/blogs/build/touch-activated-voltage-sour ce-model-218


roman (or anyone) what is the difference between v1 & v2 218s?
captnapalm
memes_33 wrote:

roman (or anyone) what is the difference between v1 & v2 218s?


v1 is nearly all SMD. v2 is mostly through-hole and is the version currently being sold.

v1 has more analog circuitry for the controls so the firmwares aren't interchangeable.
memes_33
excellent, thank you capntnapalm, and sorry for the thread hijack!
Don T
Quick update, and a mention that I am editing the first post to contain some possibly helpful de-bugging information!

Card 2:



Card 2 builds up and works as expected, once you remember to put all the parts in (See edit in original post). The Blue Card 2 has a correction of an error in the earlier versions, so I found no modifications necessary.
J3RK
I'm not building a 208, but I just wanted to say that I love these threads! I've enjoyed reading them, and the pics are great. applause
Don T
J3RK wrote:
I'm not building a 208, but I just wanted to say that I love these threads! I've enjoyed reading them, and the pics are great. applause


Thanks! If you want an even more entertaining pic, go look at the one I just added at the bottom of the original post! d'oh!
Peake
Super enjoyable, Don! Regarding the missing part...I put my PCBs up to a bright light and check for open holes, especially in tight builds such as the 259...that might help!
Don T
Peake wrote:
Super enjoyable, Don! Regarding the missing part...I put my PCBs up to a bright light and check for open holes, especially in tight builds such as the 259...that might help!


I usually do that exact thing, but for some reason, did not in this case. I probably should quit trying to build stuff at 3AM when I can't sleep!

I'll add your suggestion to the list!
Don T
And next, Card 7:

This card generates and mixes/selects all the control voltages/modulation sources for the Complex Oscillator.



There are no changes in this card from the previous version, and both versions build up and work as expected.

The 'red thing' is a hand-built prototype of jhulk's uA726 replacement board. If you want info on it, look near the end of this thread:

uA726 replacment thread here on Muff's

The only problem you may encounter with Card 7 and Card 6 is sourcing a real uA726. As mentioned earlier, if you do find a real one, expect to pay around $100 for it. The problem of getting these now is so extensive that Roman now includes a set of uA726 replacement boards with the kit. I'm not sure whose replacement Roman is using, but do know that a solution for the uA726 problem is now included in the kit. Note: This is a recent addition that I read on Roman's site, my kit was ordered some time ago and did not include these.

There is one thing I am looking into, hopefully I can find someone with a vintage, original 208 that can help verify:

In the BOM, R45 is called out as a 20K, single-turn trimpot. On the original schematics, R45 is a 100K trimpot:



It could very well be that Roman's BOM is correct, since he studied an original Easel, and it is well known that original Buchla schematics are sometimes chock-full of errors. It could also be that the opposite is true.

Here's another clue: The updated schematics on Magnus' Buchla Page show that part of the circuit as below:



In the updated schematic, R45 has been eliminated entirely, and the total value of R44 has been upped to 330K. The value of R29 and R26 have been upped also, since I'm sure there were no 330 Ohm tempco resistors (R26) available at the time, so R44 and R29 had to be adjusted proportionally. This schematic makes the case for the possibility that the old R45 was indeed 100K. If people are having trouble with scaling adjustments, and note that the original schematic shows the 20K range trimmer on the motherboard as being there to adjust to 1V/Oct, this may be why. (Incidentally, my experimental Card 6 and Card 7 are based on this updated schematic).

Hopefully someone with an original Easel, or someone a LOT better than I am at Ohm's Law calculations (Which is 99% of the population) can help figure this out. At this point I give either 20K or 100K a 50/50 chance.

That said, the circuit works just great when built to Roman's current BOM, but to be honest, I haven't started trying to calibrate either of my builds yet. It hasn't been long since I've gotten my first build to be 100% functional, and this one is obviously still in progress!

[EDIT - January 31, 2017]:

Oh yeah, almost forgot! Someone had gotten advice from davebr (I think maybe it was sduck, correct me if I'm wrong) about having very little change in tone when using the Timbre slider. davebr's suggestion was to increase the value of R9 on Card 7:



The original schematics, as well as the BOM, call for a 27K resistor in this position. My first build had the very-little-Timbre-effect issue, and I tried the suggested 82K resistor replacement on my first build, and I was very happy with the result. On this build, I used 82K when I built initially, and again I am most happy with the result. Should you choose to try 27K here on your build, and find the Timbre response lacking, give the above adjustment a try.
cygmu
Don T wrote:
J3RK wrote:
I'm not building a 208, but I just wanted to say that I love these threads! I've enjoyed reading them, and the pics are great. applause


Thanks! If you want an even more entertaining pic, go look at the one I just added at the bottom of the original post! d'oh!


The fact that someone with your skill and experience still does that occasionally makes me feel slightly less bad about myself. I still forget to insert ICs into sockets at least once per build.

I agree with J3RK: these threads are excellent. Many thanks for the effort you put in.
thermionicjunky
Don T wrote:
...The 208's balanced modulator sounds a lot more like what I expect from a ring modulator with VTL5C1 installed. Perhaps if I get time soon, I'll make and post a couple of comparison videos...


Please record any type of comparison. I've been considering this mod for years but I never have any spare vactrols.
Don T
thermionicjunky wrote:
Don T wrote:
...The 208's balanced modulator sounds a lot more like what I expect from a ring modulator with VTL5C1 installed. Perhaps if I get time soon, I'll make and post a couple of comparison videos...


Please record any type of comparison. I've been considering this mod for years but I never have any spare vactrols.


I will do my best. I need something better to record with than my iPhone though.
Don T
Just added another edit to the original post, to the general troubleshooting tips:

"2A. If you put your chips in sockets, make sure none of the pins got folded under and are not making contact."

I found a chip that had done that on my Balanced Modulator card a couple months ago, forgot to mention it.
Don T
Just added another edit and attachment to the original post: A very good image of the 208 Mother Board schematic. You'll probably need a piece of poster paper to print it out large enough, because it combines both halves of the motherboard schematic into one continuous image. I've found it very useful for debugging.

I cannot remember where online I found the image, so if anyone knows who should get credit, please let me know!
davebr
Don T wrote:
Just added another edit and attachment to the original post: A very good image of the 208 Mother Board schematic. You'll probably need a piece of poster paper to print it out large enough, because it combines both halves of the motherboard schematic into one continuous image. I've found it very useful for debugging.

I cannot remember where online I found the image, so if anyone knows who should get credit, please let me know!

I photoshopped the two halves together, cleaned it up, and posted a PDF on my Buchla 208 V2 Stored Program Sound Source Module page. I also combined the later version motherboard schematic. While this looks nearly the same, it has been slightly straightened so someone either did the same work or did some post processing on mine. I can't claim it as it isn't truly identical.

Dave
Don T
davebr wrote:
Don T wrote:
Just added another edit and attachment to the original post: A very good image of the 208 Mother Board schematic. You'll probably need a piece of poster paper to print it out large enough, because it combines both halves of the motherboard schematic into one continuous image. I've found it very useful for debugging.

I cannot remember where online I found the image, so if anyone knows who should get credit, please let me know!

I photoshopped the two halves together, cleaned it up, and posted a PDF on my Buchla 208 V2 Stored Program Sound Source Module page. I also combined the later version motherboard schematic. While this looks nearly the same, it has been slightly straightened so someone either did the same work or did some post processing on mine. I can't claim it as it isn't truly identical.

Dave


Dave,

You are correct, the image is yours. When I went to your page a second ago, it showed me that I had indeed clicked on that link. I hadn't seen the later version yet, that will make an interesting study later. Thanks for all you do, and all the info you share on these projects! You are the "go-to" source!
Don T
For today, Card 9, and a small note on constructing the motherboard:

Card 9 builds up as expected. There are a lot of diodes on this one, so double-check their direction.



When I first tested this particular Card 9, I got a little wavefolding action, but nothing but clicks when it was being fed the Sine wave generated on Card 8. After running through part of the troubleshooting checklist, the culprit was found, a not-too-easy-to-spot solder bridge:



For comparison, the correct version:



After clearing the bridge, the card worked just fine, and the wavefolding was even better. davebr has photos of all the V2 cards up on his website if you want a quick reference to check your cards against. If you want a higher-res closeup of a certain card, please feel free to send me a PM and I'll try to get a decent photo of what you need. Remember the troubleshooting checklist folks! It just may save you money on hair replacement treatments...

On to a note on the motherboard:

I noticed this awhile back, but forgot to point it out earlier. On the new, blue V2.1 motherboard, there is now an octagonal pad to designate the cathode (-) lead of every LED, even the ones not visible in the photo. On almost every LED I have ever seen, the cathode lead is the shorter of the two, even if the LED doesn't have a flat spot to designate the cathode. This may not seem like much, but if you have built one of the previous version before that had nothing but identical round pads for all the LEDs, this is a most welcome addition. It is REALLY easy to get lost on that giant motherboard, and to even lose track of which way is up if you're looking at it too closely. By the way, the octagonal pad appears on both sides of the board:



Another update soon, I hope.
Don T
OH yeah, I haven't mentioned this yet, but: When you are done, wash the board to get rid of the solder flux residue!! I don't care if it is the "no-clean" kind! The only way to truly know something isn't going to damage the board over time is to get rid of it! I've made many a dollar (in huge multiples) repairing gear that the factory and/or builder didn't bother washing the board when it was finished. Trying to find all the places on a piece of equipment where the solder pads have become separated from their traces due to corrosion is frustrating, time consuming, and if someone else is doing it for you, expensive!



See, nice and clean. If you are troubleshooting a faulty board, sometimes washing it helps to find a bad solder joint, missing solder joint, or a solder bridge.

I won't go into "how" right here, since the method varies with the type of rosin in the solder used. That said, I do not recommend using those spray cans of flux remover at home. If you don't know why, just trust me. If you do know why, no explanation is needed.
Peake
Don T wrote:
That said, I do not recommend using those spray cans of flux remover at home. If you don't know why, just trust me. If you do know why, no explanation is needed.


Oh yes, learned that one... Thanks for the insight into Card 9. I've checked all component values, tested in-circuit for all resistors, caps, and diodes, confirmed diode orientation, checked against Dave Br's images for solder bridges, tested continuity on all of the bottom traces point to end point, swapped out all ICs, confirmed power to at least the 4136. Not a peep. Some of my caps are different than what I see on your build; I'll take it the three green film caps are ones you had in stock, etc.
MrRoper
Thanks so much for this thread Don T.

I havent built one of these yet as I was quite intimidated by all of the fixes needed on the old board but this new thread as well as Davebr's page has been a god send!

Currently saving to get in on this!

Also, sorry to go off track, but why are the aerosol flux removers a bad idea? Can you recommend something else?
Don T
Peake wrote:
I'll take it the three green film caps are ones you had in stock, etc.


Yes, most of the film/ceramic caps on my builds are recycled. The green ones in that photo came from a dead Roland JX-3P. If you see old-style ceramic disc caps in the photos, they came from either a dead Korg Poly-61 or a Polysix. Any part I recycle is tested to be in spec before it is soldered in.

MrRoper wrote:

Also, sorry to go off track, but why are the aerosol flux removers a bad idea? Can you recommend something else?


As I mentioned earlier, the method will vary with the type core of your solder, but for starters I recommend scrubbing with an old toothbrush and at least 90% isopropyl alcohol, followed by scrubbing with detergent and water. That should take care of most things. As for the aerosol stuff, since I see you are in London, I imagine it isn't even legal there! Let's just say that most of them are a mixture of all the most dangerous substances studied in an organic chemistry class.

Card 8 should be ready to go this afternoon!
muncky
Any tips for the over enthusiastic who have added the sliders, switches and trimmers but not cleaned their motherboard yet? hmmm.....
Don T
muncky wrote:
Any tips for the over enthusiastic who have added the sliders, switches and trimmers but not cleaned their motherboard yet? hmmm.....


Either leave it, or just clean the side away from the sliders. The switches and trimmers on the BOM are all sealed, therefore waterproof, as well as being safe from most other chemicals. Plain water shouldn't hurt the sliders once it is allowed to evaporate, but I wouldn't let anything else get inside them.

[EDIT]: When all is said and done, cleaning every solder point on the motherboard will be quite difficult. In fact, I never cleaned the solder joints from my LEDs and banana jacks, as the panel was already in place. I figured on gambling on the "No-clean" type of rosin. If it had been the old type of brown sticky rosin found in old 60/40 solder, I would've found a way to clean it off.
Don T
As promised earlier, Card 8:



A few, not-quite-Earth-shattering notes on construction:

First, as noted earlier on the other cards that there was a small pad added to indicate the + lead of the LED for any vertically-mounted Vactrols, Card 8 does not have this feature. Instead is has a big honkin' giant pad on the + lead (Simply because there is a trace on top that connects there. This is the only vertically-mounted Vactrol like this):



Next thing of note, this card is the one where your selected 2N4339 goes. This one had an Idss of .733, and even before trimming it has a nice sounding Sine wave. Please refer back to the original post for a diagram showing which resistors and diodes should be matched in the Sine shaper circuit:



Ok, stay with me here, this next part is spread out over a few photos. There are only 2 errors on the motherboard, both small, and both easily corrected. This is where you correct one of them, and requires no modification to the motherboard. It is a simple and elegant mod, courtesy of davebr's website. On Card 8, you need to bridge Pin 11 and Pin 12 on the edge connector. Here's my method:

When you tack-solder the connectors in as suggested earlier in this thread, make sure you leave Pins 11 and 12 unsoldered. The pins are counted from Left-to-Right looking at the back of the card, with Pin 1 on the Left:



Then take a resistor leg and make one of these:



Then insert it into the grooves on top of the connectors of Pin 11 and Pin 12:



Then finish soldering the connectors onto the card. For future reference when tracing signals and/or bugs, on all the cards the pin numbers are counted from Left-to-Right, looking at the back of the card, with Pin 1 on the Left. Seems counter-intuitive to me, but it is what it is, and this is the way they are numbered on the schematics:



And yes, I washed the board after testing it! cool
Don T
It appears there is an error on the motherboard schematics. This was discovered when helping someone diagnose a troublesome bug. The connections crossed out in the photo below between Card 8 and Card 9 do not exist:



Not only do these connections not exist on the motherboard, but Pins 10 & 11 on Card 8 and Pins 4 and 7 on Card 9 are not connected to anything on the cards themselves.

This error appears on all versions of the motherboard schematic that I have seen.

Carry on!
davebr
Don T wrote:
It appears there is an error on the motherboard schematics. This was discovered when helping someone diagnose a troublesome bug. The connections crossed out in the photo below between Card 8 and Card 9 do not exist:



Not only do these connections not exist on the motherboard, but Pins 10 & 11 on Card 8 and Pins 4 and 7 on Card 9 are not connected to anything on the cards themselves.

This error appears on all versions of the motherboard schematic that I have seen.

Carry on!

I have noted that there are discrepancies between the early schematics and the 208. I don't specifically remember if it was these pins or something else but I always view the motherboard schematic as being close, not exact.

Dave
lucid
davebr wrote:
Don T wrote:
It appears there is an error on the motherboard schematics. This was discovered when helping someone diagnose a troublesome bug. The connections crossed out in the photo below between Card 8 and Card 9 do not exist:



Not only do these connections not exist on the motherboard, but Pins 10 & 11 on Card 8 and Pins 4 and 7 on Card 9 are not connected to anything on the cards themselves.

This error appears on all versions of the motherboard schematic that I have seen.

Carry on!

I have noted that there are discrepancies between the early schematics and the 208. I don't specifically remember if it was these pins or something else but I always view the motherboard schematic as being close, not exact.

Dave

well on schematics I used for debugging it is like this:
board 8

and board 9

so from this point of view makes sense to not have the traces there[/img]

what makes me more crazy was that on schematics for board 3 there is part which does not exist in reality on board:

but maybe it is just wrong set of schematics I used. everything else was fitting to BOM and real layout on boards.
Don T
davebr wrote:

I have noted that there are discrepancies between the early schematics and the 208. I don't specifically remember if it was these pins or something else
Dave


If you remember that it was something else, please let us know!
Peake
This just gets better and better. Thankfully the clone works as-is.
tarandfeathers
Don T wrote:
For future reference when tracing signals and/or bugs, on all the cards the pin numbers are counted from Left-to-Right, looking at the back of the card, with Pin 1 on the Left. Seems counter-intuitive to me, but it is what it is, and this is the way they are numbered on the schematics


They're that way round so that, when mounted on the motherboard, pin 1 is at the top and the highest numbered pin is at the bottom. There was probably no thought that cards would be tested separately from the motherboard so it makes sense to have the numbering that way round.
Don T
Just curious, has anyone else finished their Blue V2.1? My panel and sliders have yet to come in, so I've been checking all my cards built so far in my completed V2 208. Trying to help a fellow wiggler debug something, and I want to make sure there isn't an issue with the V2 vs. V2.1 motherboards, specifically if anyone has a working Timbre section or not.

Also, anyone else that would like to contribute to this thread, please do! Until my panel and sliders arrive, I'm rapidly running out of stuff to build! (especially since I'm going to be out of town all of next week, and possibly the week after as well).

I've almost finished Cards 6, 10, 11, and 12, so hopefully I'll have those up before the weekend.
Don T
tarandfeathers wrote:
Don T wrote:
For future reference when tracing signals and/or bugs, on all the cards the pin numbers are counted from Left-to-Right, looking at the back of the card, with Pin 1 on the Left. Seems counter-intuitive to me, but it is what it is, and this is the way they are numbered on the schematics


They're that way round so that, when mounted on the motherboard, pin 1 is at the top and the highest numbered pin is at the bottom. There was probably no thought that cards would be tested separately from the motherboard so it makes sense to have the numbering that way round.


Fair enough. That doesn't change the fact that I'm easily confused, though dizzy
Peake
Shout-out to Don for the enormous amount of help and contribution to the community!
muncky
nanners
bsilverberg
Peake wrote:
Shout-out to Don for the enormous amount of help and contribution to the community!


Couldn't agree more!!!
Don T
Thanks for the kind words, guys!

Anyhow, meant to post Card 12 tonight, but wound up just one part short of completion, a 470uf axial cap. Luckily, a quick Radio Shack run tomorrow morning should take care of that issue.
Synesthesia
Just adding to the shout out wink

I am not building a blue 208 - I have a non blue rev 2 finished ( with a broken reverd ) and another one to build.

but i still check the thread everyday - so many usefull tips and infos!
Don T
Today's installment - Card 12:



I've got a few notes on this card, some strongly suggested, some optional:

The first item (and jumping ahead of my normal assembly order a bit) is strongly suggested. When mounting C13, let it be quite high above the board on long leads, then bend the legs towards the connector end of the card, then bend the body of the cap to be vertical again, as shown below:



Why? Here's why:



You still won't get L1 to be flush with the board, but at least this way it won't be flopping around all over the place. Yes, I used a film cap for C13 instead of a ceramic disc, but modern ceramic discs are about that thick anyway. Plus, I don't care how thin C13 is, that inductor isn't going in there unless you mount it as suggested, or you are ok with it being way above the board.
Do be careful how far forward you mount C13, it will still need to clear the Molex connector:



The next item could cause frustration with assembly for those caught unaware - Several components have one or more leads attached directly to the integral heatsink on top of the board. If you think that copper-flooded area is too puny to be an effective heatsink, just wait until you try soldering the aforementioned components from the back of the board. Outlined in red below are all the locations I'm talking about:



Make sure the iron is hot, and don't be afraid to hold the iron on the lead and pad a little longer than normal before applying solder. I suggest putting a tiny dot of solder on the tip of the iron to transfer heat better, then putting the tip/solder dot in firm contact with the lead and the solder pad, counting to seven, then applying solder. IF the solder doesn't want to melt and flow in almost immediately, you may not have your iron hot enough. This is one of the times where having the iron slightly too hot is better than having it slightly too cold. If it's too cold, you'll be more likely to cook the component you're soldering before the solder flows sufficiently (especially the three 4.7uf electrolytic caps involved, that stuff stinks when it boils). For reference, I use a Hakko N452 soldering iron, which is rated 15W, plugged directly into the power strip with no temperature control. The "Count to seven" method above works just fine, but it isn't strong enough to solder those points much faster than that. Everywhere else, it's fast as lightning, even with the lead-free (96% Tin, 3% Silver, 1% Copper) solder I use.

Next, this item is completely optional - I mounted C2, which is a fairly large axial electrolytic cap, on a small pad of Scotch double-sided foam tape (don't forget to peel the top backing layer off before mounting the cap!):



Two reasons for this, most likely to not happen, but an ounce of prevention is worth apound of cure. One is to isolate the body from the integral heatsink, which is also a ground plane. If for some reason the insulation on the body of the cap fails, all of your reverb signal will be dumped to ground. C2 AC couples the audio signal from both LPGs to the reverb driver. Second, if you move your 208 around a lot, eventually, if the cap is allowed to flop around, metal fatigue could make a lead snap, or the rubbing could wear through the cap's insulation. Like I said, neither of those is likely to ever happen, but I have made repair $$ from fixing similar faults in other gear before. Also, as mentioned earlier in the thread, this in one place you'll definitely want to float resistor and cap bodies above the board just a little bit, even if you chose not to do it elsewhere.

[EDIT]: (I knew I forgot something) I used a 470uf cap for C2. The schematics call for a 390uf cap. Good luck finding one! davebr used a 330uf cap for C2, which is also perfectly fine.

And, up next, reverb return -

DISCLAIMER: I have not tested this yet, on either build, because I stupidly forgot to order the reverb tank bracket for my first build, so I haven't mounted or tested my reverb tank yet.

Anyhow, there has been discussion on not connecting the reverb return cable to the places provided on the motherboard, and using shielded cable to connect the reverb return directly to Card 12. If you've looked at the parts placement photo, or the one above, and wondered what the hell Pins 1A, 1B, 1C, and Pin 2 are for, they are apparently intended for this purpose. I suggest ignoring Pins 1B, 1C, and Pin 2. Pin 1A is directly connected to Pin 5 of IC1, which according to the schematics (and verified by tracing the motherboard and Card 12) is the input for the Reverb Return Signal. If you want to use shielded cable (And why wouldn't you?) I suggest one of two ways, depending upon which side of Card 12 you want to attach the cable. If you want to attach it from the component side, here you go:



The indicated lead of R1 is indeed ground. I checked. Twice.

If you want to mount the cable from the trace side of Card 12, which means you'll need to route the cable around the back of the card, but have more room to make the connections, here is the pic:



No matter which side you choose to mount your shielded cable, make sure to cut the trace coming from Pin 13 of the Molex connector to Pin 5 of IC 1. I suggest cutting at the point shown in the photo.

If you choose not to mess with any of the trace cutting/shielded cable stuff, I'll show you later where on the motherboard the reverb return cable connects. I'm told that using the directly-connected shielded cable does greatly reduce noise in the reverb circuit. Perhaps davebr can weigh in on the merits of this.

Note: The previous version of the 208r has these pads for the reverb return available also.

One last thing: Do NOT use IC sockets for the LM380 chips!! They are ICs 2, 3, and 4. They will be much happier mounted directly to the board, in direct contact with the integral heatsink. Hmm, "Happier". I shouldn't anthropomorphize electronic components, they hate that...
Don T
On tap tonight - Card 10 and Card 11:



Each card contains an example of the famous Buchla Lopass Gate. Card 10 is also where the external preamp and the envelope detector live, and Card 11 also takes care of some audio signal routing duties.

Both cards build up with no problems, and work as expected.

The only things worth mentioning as far as build notes go are: Like cards 3 and 4, make sure the bottoms of the 2N1711 transistors float above the PCB a little bit. Next, there are many, many vias and resistors on these boards, and as a result there are many places where there are tight clusters of holes. Take your time stuffing the boards, and study the part placement photos carefully. When you are first getting started stuffing the boards, it could be easy to put a resistor lead in the wrong hole. I say "could be" because I somehow didn't manage to make that mistake, but there were many times I almost put a lead in the incorrect hole. As the board gets more filled, keeping track of where you are obviously becomes easier.

While I'm thinking about it, and it applies to these two boards especially, a few people have asked me about the capacitors I have selected. To be honest, quite a few caps that you see on the boards I have built that appear in this thread (as well as most of the other gear I've built/repaired) are actually recycled. I figure why buy a bunch of brand new parts if you already have perfectly good ones lying around in old dead equipment that are perfectly good, and in some cases better than what the BOM may call for. It's certainly cheaper, and environmentally sound. That said, all the electrolytic caps are brand new, I rarely reuse and old electrolytic. As in, almost never. Every cap I recycle is tested before being soldered in to the circuit.

For the curious, if you look at the photo above, and photos of the other boards in this thread, you may notice some clear green film caps. Those came out of a dead Roland JX-3P. The clear yellow film caps, as well as any old-school ceramic disc caps, came out of either a Korg Polysix or a Korg Poly-61. The 4.7nf caps in the photo above came from various pieces of dead Bang & Olufsen hi-end audio gear. The tantalum caps are new. The 220pf styrene caps I used because I had them, and since they are part of the filter section of the LPG, why not?

Speaking of the filter section, the BOM calls for 1000pf ceramic caps for C6 and C12 on Card 10, and C2 and C6 on Card 11. On the original schematics, these are all 910pf ceramic caps. Card 10, C6, and Card 11, C2, are part of the filter. For the sake of authenticity in frequency response, I did indeed use 910pf Caps in those positions, even though they cost a little more (Considering how much has been spent on this already, what's a few cents more per cap?). Card 10, C12, and Card 11, C6 are part of the LED driver circuit, so I used recycled film caps (read: FREE) in those spots. Some might call me a cheap bastard, but if you found out I spent $1 each for those blue IC sockets, mostly because they happened to be blue (the decoupling caps were an added bonus, but had to be removed on quite a few of them), you would know that the term "cheap bastard" is not true. Well, not totally true anyway...

The only card remaining for this particular build is Card 6, the Modulation Oscillator. I'm preparing another one of jhulk's prototype uA726 replacement boards to go on it. It will be slightly different from the other one, as jhulk as suggested a few tweaks to improve it since I built the first one.

Again, if anyone else is building one of these, feel free (please!) to add to the thread. I'll be away from my soldering iron for a least a week, perhaps two. I have a teaching/clinic gig in another state. Besides, I haven't even ordered the sliders for this sucker yet!
heapish
Hey, just wondered if someone could help? I've just been weighing this project up (e.g. Can I afford). Is there a rare parts kit? If so what's the price? Also, whats the overall Mosher cart cost?
Cheers
Don T
heapish wrote:
Hey, just wondered if someone could help? I've just been weighing this project up (e.g. Can I afford). Is there a rare parts kit? If so what's the price? Also, whats the overall Mosher cart cost?
Cheers


I haven't kept up with parts cost so much, since I didn't source everything from the same place, or all at once. As a for instance, you cannot get the sliders, the reverb tank, and a few of the chips and transistors from Mouser. The switches are sourced from Digi-Key, at least in the US.

As for a rare parts kit, I am not aware of anyone making such a thing available. Off the top of my head, here are the "rare parts" you'll need to find, with quantities in parenthesis, plus any notes on the part:

2N3565 - (2) - It is best if these are matched for Vbe, so you will need to get a few and test.
MC846 - (2) - Quad 2-input NAND gate, DTL logic.
uA726 - (2) - Good luck finding these for less than $100 each. They have now become so rare that Roman provides a pair of uA726 substitute boards in the kit. There are other alternatives becoming available
DG200A - (1) - TO99-10 package. Available for between $5 - to - $100 depending upon the source. These are actually current manufacture in the TO99 package (guess which ones cost $100!).

Everything else is currently available, but not all from the same vendor.

Perhaps I should add this list to the OP...
Peake
I believe there are one or more 2N4341 and 2N4340 as well as a single selected 2N4339? UTSource have them...but if there's a selected 4339 you'll have to get a few and DIY...
jhulk
i can do a dip to to9910 conversion board which allows the dip version of the chip which is a lot cheaper.

if any one likes

the ua726 replacement that i do is also cheap i have pcbs here in a few weeks
Peake
If it's not obvious I'm the builder whose Timbre wasn't functional. Don has been an amazing help as has Dave B's amazing build page. I wanted to chime in noting that the issue is on my board 7 and that the mother board is fine, everyone should build with confidence if anyone hasn't yet finished.

My board 7 C2 was 470pF, not 47nF. All is well in Timbrehood.
Don T
Peake wrote:
I believe there are one or more 2N4341 and 2N4340 as well as a single selected 2N4339? UTSource have them...but if there's a selected 4339 you'll have to get a few and DIY...


I started to put those on the list, but 2N4339, 2N4340, and 2N4341 are available at Mouser still. I guess I'll add them to the list when I revise the OP.
rampy
heapish wrote:
Hey, just wondered if someone could help? I've just been weighing this project up (e.g. Can I afford). Is there a rare parts kit? If so what's the price? Also, whats the overall Mosher cart cost?
Cheers


I believe MW user Boops is still selling rare parts kits for the 208. I got mine a couple months ago for my V2 208. Without the ua726 its 110euro plus shipping. I think paid 275euro with the ua726


Original parts NOS

2N4339/ need x2
2N4340 / Need x2
2N3565 / Need x2 NOT INCLUDED USE PN3565 /610 pn3565 1 USD the both at mouser and reverse the pinout
2N3806 for the LS 352 x 1
MC 846P Need x2
Ua 726 original vco tested dc 83xx/ 60 eu ea need x2
DG200BA date code 7900 Need x1
2n4341 date code 7918 x2

http://https://www.muffwiggler.com/forum/viewtopic.php?t=117391&highli ght=
Don T
rampy wrote:

I believe MW user Boops is still selling rare parts kits for the 208. I got mine a couple months ago for my V2 208. Without the ua726 its 110euro plus shipping. I think paid 275euro with the ua726


Oops, forgot about Boops...
lasesentaysiete
has anyone successfully used Roman's uA726 replacement adapters that come with the latest rev 2.1 board sets?
muncky
Don T wrote:
On tap tonight - Card 10 and Card 11:



Each card contains an example of the famous Buchla Lopass Gate. Card 10 is also where the external preamp and the envelope detector live, and Card 11 also takes care of some audio signal routing duties.

Both cards build up with no problems, and work as expected.


question DonT- having now got my mamma card, I'm trying to finish off the motherboard, and some what stumped on the link between the Preamp input and the switched TiniJax - any tips on best way to approach so the cabling is done right and ready to link up when Card 10 is done?

also, would this Sommer cable be effective:
http://shop.sommercable.com/en/Cables/Bulk-Cables-Audio/Patch-Mikrofon kabel-SC-Goblin-200-0356.html

or should I just stick with with Dave Brown's recommended RG174 coax?

thanks once more
Peake
I'll chime in and hope Don posts a more thoughtful reply...the preamp input jack grounds the middle pin. Looking at its rear, pins 1 and 2 are grounded, going left to right; pin 3 is audio.
Don T
muncky wrote:

question DonT- having now got my mamma card, I'm trying to finish off the motherboard, and some what stumped on the link between the Preamp input and the switched TiniJax - any tips on best way to approach so the cabling is done right and ready to link up when Card 10 is done?

also, would this Sommer cable be effective:
http://shop.sommercable.com/en/Cables/Bulk-Cables-Audio/Patch-Mikrofon kabel-SC-Goblin-200-0356.html

or should I just stick with with Dave Brown's recommended RG174 coax?

thanks once more


First, follow this instruction from Peake

Peake wrote:
...the preamp input jack grounds the middle pin. Looking at its rear, pins 1 and 2 are grounded, going left to right; pin 3 is audio.


Ideally, you would run these connections with a 2-conductor cable that is shielded also, such as the Sommer cable you linked. Use the two conductors for signal and ground from the jack to the connections on Card 10, and then ground the shield at the ground connection at Card 10, but not at the jack.

That said, I think the Sommer cable you linked may be kind of thick for this purpose. I'm not sure how stiff it is either, and whether or not it'll put stress on either the jack or the connection on Card 10. I don't have my motherboard in front of me to photograph, but there is a notch cut in the back near the Card 10 slot for routing the input cable. You'll want whatever cable you use to fit comfortably there, without the stress constantly pushing the cable against the lip of the boat. Probably nothing would happen as far as wear-through goes, but it pays to be thorough.

Long story short, davebr's solution may be the best, unless the Sommer cable is thinner and more flexible than I think. No matter what, I would rig a plug and connector on Card 10 as Dave did, and make note of Dave's use of a cable tie to keep the cable from flopping around too much and putting stress on the connector. (There is a typo on Dave's site, he talked about the preamp cable running to Card 8, but the photo makes it obvious he meant Card 10)

Hope this helps!
muncky
That's really helpful, thanks both SlayerBadger!

On the cable, I suspect you're right Don, as it's definitely a bit stiff. Will get something more suitable
malnatim
i've finished my 208r. i wanted to say many thanks to davebr and donT. all the info they've shared online made the build straight forward. i thought i'd share a few little things from my build. maybe they'll be of use to someone.

having looked at the orig. 208 on davebr's site, i did socket the LM380 and put heatsinks on them. i soldered the 0v pins of the sockets to the front of pcb. using 330uf rather than 390uf means there's room for heatsink on ic3.
http://www.modularsynthesis.com/buchla/208/buchla_208.htm



i used a beater wrapped in electrical tape to make a support exactly the right thickness to fit between alps slider pots and panel. pushing on the cards and supporting the panel with your other hand, there's no stress / flexing to mother board.




i put r74 + r78 on the card side so i could clip them off and try other values. i've used 680k and the range of the fine tune pots is now much finer. pot centred and complex osc at C3 the fine tune is G#2 to D3. i've added 470k on the mother board from -15v going to pin 3 of board 7 to add a neg. offset to the CO pitch. a slightly lower value resistor here would probably be a bit better, but you can get there with the offset trimmer.




slightly off-topic, but my fav. easel mod is providing a support rest for the 218r. it's just off-cuts of wood and felt, but it dampens the thin, hollow sound and stops 218r flexing. imo it's a massive improvement for little-to-no cost. the feel is now great.

Oscilloclast
Quick question on hooking up the reverb tank: I figured out which side is the input and which side is the output, but for the two pins on the input and output does anyone know which pin is the signal and which one is the ground (or are they interchangeable)?

Thanks
Peake
Blue is signal and black is ground...that is, the wire coloration on the connectors mounted to the reverb signal I/O pins...not interchangeable. Don't solder directly to the metal signal pins on the reverb tanks; the wire going to the transformer bobbin will burn through, I found out the hard way. Note the color coding of each side (I believe they're reversed between in and out) and remove the output connector, clip the wire about an inch off of the connector, strip a bit of each, tin, and having heatshrink already placed on the wires, solder up the shielded connector then move up the heatshrink and shrink it. Or, as some here have done, connect the shielded cable directly to a header that fits the reverb.
Oscilloclast
Great, Thanks for the info.
muncky
Scariest moment in five years of DIY... hope Ingot it right...!

Dimitree
A question for those who completed the project, before I decide to jump in: how is the VCOs keyboard tracking? Can it track for 2-3 octaves and play chromatically? And what about external CV tracking?
Peake
I got 3 octaves of tracking and stopped there; couldn't get the HF tracking pots (modified to 500K so they actually did something) to do anything more than delinearize the second and third octaves in favor of hitting the fourth. I calibrated like this:

-As Dave Brown says on his page, set the front panel Keyboard trimmers to the middle.
-Tune oscillators to unison with a known frequency or keyboard note, have a tuning reference running. This is with your CV source putting out 0V.
-Play three octaves up. Tune and Fine Tune Easel oscillators to unison with the reference pitch with the front panel controls.
-Play the bottom note which outputs 0V. Set Range trimpots to tune for unison.
-Play 3 octaves up again and tune the front panel for unison.
-Play 0V/3 octaves down again and tweak Range trimmers for unison.

This is the opposite of what I'm used to but it works. It does not allow for the HF tracking to not delinearize the 3rd octave as you attempt to set the 4th to unison, even when then adding further Range trimpot scaling.
synthi
Looking at the schemos seems that +5V is only used for the sequencer on card #1.
Also I see an annotation for using +12V there just changing two resistors, did anyone this mod for skipping +5V supply??

Thanks!
Don T
synthi wrote:
Looking at the schemos seems that +5V is only used for the sequencer on card #1.
Also I see an annotation for using +12V there just changing two resistors, did anyone this mod for skipping +5V supply??

Thanks!


+5V is used in more places than Card 1. Can't remember everywhere off the top of my head, but it powers the MC846 chips on Card 9. This means the timbre section will not work without it. Seems like the sine wave wasn't working without +5V being present either. I learned all this when the 7805 in my bench power supply broke a solder joint.

You are using the older schematics for reference, yes?
synthi
yes, older schemos... I was thinking only the sequencer need the +5V line... Thanks Don!!
muncky
Don T wrote:
On tap tonight - Card 10 and Card 11:



Each card contains an example of the famous Buchla Lopass Gate. Card 10 is also where the external preamp and the envelope detector live, and Card 11 also takes care of some audio signal routing duties.

Both cards build up with no problems, and work as expected.


Question, Don T - did you stick with the 1uf tantalum cap at c4 on Card 11, or swap to 47uj as suggested by Dave Brown? Be useful to know your thoughts, especially as I don't have a 47uf tantalum lying around at the moment...!
Don T
Hi all, old computer died, just replaced it, I wasn't ignoring anybody.
muncky
Hey Don T, now you're back online, don't suppose you're set for the final instalment with the motherboard? Your posts have been a bible for me assembling this little monster nanners
the bad producer
Yo muncky, is this the one I'm supposed to read, or am I gatecrashing the wrong party?! Dinner at the Y
muncky
There's a stack of good stuff in here, but a lot of bonus material in the original thread:
https://www.muffwiggler.com/forum/viewtopic.php?t=127084&highlight=
the bad producer
thumbs up
Don T
muncky wrote:
Hey Don T, now you're back online, don't suppose you're set for the final instalment with the motherboard? Your posts have been a bible for me assembling this little monster nanners


Soon, soon (I hope). Luckily most of the motherboard construction is straightforward, as long as your remember to bridge pins 11 and 12 on Card 8, and remember to run the jumper to pin 7 on the preset card slot.
PacificState
Just picking up on a post from a few months back (thanks, DonT!) - as only the Xvive vactrols are readily available at this point, is the VTL5C1 definitely the way to go? There's some suggestion of variation between batches in the discussion above - just wondering if the VTL5C3 sounds obviously 'off' in this case.
J3RK
PacificState wrote:
Just picking up on a post from a few months back (thanks, DonT!) - as only the Xvive vactrols are readily available at this point, is the VTL5C1 definitely the way to go? There's some suggestion of variation between batches in the discussion above - just wondering if the VTL5C3 sounds obviously 'off' in this case.


Just a little only-somewhat-related info on this. I just built two of my Quad Gate (four LPG) modules using XVive 5C1s. There was very little to no variation between any of them. They all sounded the same more or less, and looked very similar on the scope. That's 8 vactrols total, ordered from CabinTech. I'm not building Buchla gear, so as far as that part goes, I'd wait for Don to chime in. However, so far, I have no complaints at least with consistency of the 5C1 version. I suppose more builds and time will tell, but for now, not too bad, and the price is good.
masterofstuff124
plenty of cheap vactrol options

lcr0202(aliexpress)
fake vtl5c?

both discussed in this thread.

https://www.muffwiggler.com/forum/viewtopic.php?t=146230&postdays=0&po storder=asc&start=0

i am also in need of a complete set of vactrols for my 208 build.

seems like excellitas 5c1 are available here

http://store.chriselectronics.com/product.php?cat=&page=1&productid=19 762


as per dons recommendations and my own personal preference(larger functionality range and not caring about authentic tone.)

I should get
4 excellitas 5c1 for modulator
10 xvive xtl5c1 for everything else from cabintech



but i am tempted to get the cheap vactrols working......
Don T
PacificState wrote:
Just picking up on a post from a few months back (thanks, DonT!) - as only the Xvive vactrols are readily available at this point, is the VTL5C1 definitely the way to go? There's some suggestion of variation between batches in the discussion above - just wondering if the VTL5C3 sounds obviously 'off' in this case.


Hi! Check out the second post on this thread (You'll have to scroll a bit, the first post is pretty long), I had moved some info I posted on another thread so that it would be available here. If that post doesn't answer your question, let me know, and I'll try to elaborate.
PacificState
Thanks! Yup, I read it, but wasn't sure - it seems there's no way to get hold of the Excelitas VTL5C3 any more, so new builds should always use the Xvive VTL5C1? I guess the other part of the question is - how different do the VTL5C1s sound? You did reference the effect, but I was wondering if it was subtle or something more obvious.

Apologies if this in in the minutiae!
Don T
PacificState wrote:
Thanks! Yup, I read it, but wasn't sure - it seems there's no way to get hold of the Excelitas VTL5C3 any more, so new builds should always use the Xvive VTL5C1? I guess the other part of the question is - how different do the VTL5C1s sound? You did reference the effect, but I was wondering if it was subtle or something more obvious.

Apologies if this in in the minutiae!


Tonally, there really isn't a noticeable difference. The difference lies in the rise time and settling time of the vactrol itself. Yes, the rise time of an attack does indeed have an effect on perception of timbre (A discussion for another time), but all the above mentioned vactrols are pretty quick. It's the settling time that makes the most difference here. 5C1 is fast enough that you may need to add just a touch more decay time to match the decay of an original 5C3. I found the Xvive 5C3 to have an excessive settling time, even with the EG set to its shortest decay. Admittedly, I had a small sample size, but to me the difference between the Excelitas 5C3 and the Xvive 5C3 was significant enough that I would rather use the Xvive 5C1 instead. This is just my opinion though.

Hope this helps.
Don T
I have some news for people that may be having trouble sourcing a rare part, or are just too cheap to want to spend $4 a pop for them...

...I'm talking about the MC846P chips that do the wave folding work on Card 9. Tonight while I was digging around looking for the temperature probe that came with my DMM, I found a pair of old DM7400 chips, which is a quad NAND gate with the same pinout as the MC846P. It is, of course, a TTL chip instead of a DTL chip like the MC846P. I had been thinking about the possibility of swapping them awhile actually, so after finding the long-lost temperature probe, I got bored and...





...I'll be damned, it worked!. In fact, I found no noticeable difference in the range of the Timbre control, or the tone. In other words, to my ears they sounded identical (And for those that don't know me well, I've made most of my adult income either using my ears, or by teaching younger musicians how to use theirs). Even played back through an NAD amplifier and a pair of these, they still sounded identical:



If you don't know what that speaker is, you have my condolences cool (KEF Reference Series 104/2)

P.S. - No, I have not yet tried it with any other variety of 7400 (yet).

[EDIT 07-11-2017] Check my most recent post, dated 07-11-2017, on the above subject!
davebr
Don T wrote:
I have some news for people that may be having trouble sourcing a rare part, or are just too cheap to want to spend $4 a pop for them...

...I'm talking about the MC846P chips that do the wave folding work on Card 9. Tonight while I was digging around looking for the temperature probe that came with my DMM, I found a pair of old DM7400 chips, which is a quad NAND gate with the same pinout as the MC846P. It is, of course, a TTL chip instead of a DTL chip like the MC846P. I had been thinking about the possibility of swapping them awhile actually, so after finding the long-lost temperature probe, I got bored and...

...I'll be damned, it worked!. In fact, I found no noticeable difference in the range of the Timbre control, or the tone. In other words, to my ears they sounded identical (And for those that don't know me well, I've made most of my adult income either using my ears, or by teaching younger musicians how to use theirs). Even played back through an NAD amplifier and a pair of these, they still sounded identical:

P.S. - No, I have not yet tried it with any other variety of 7400 (yet).


Note that the MC846 RTL part has an open collector with an internal pull up resistor. The outputs of two pairs of two gates are tied together forming a wired or configuration. Although your DM7400 part fits it is not an open collector part so the outputs tied together are fighting. I don't know what the output voltage level is when these gates fight but it is likely not a valid logic level. Note that you could add diodes and pullup resistors on the four outputs to turn this into a wired or configuration, but with the diodes you now don't meet Vil specs with TTL. You could do it with a CMOS gate and then the small diode drop doesn't matter.

I have used CMOS gates with diodes and pullup resistors on a 285 where Don also used the MC846 part in a similar configuration. When I decided to build my own personal 208 I wasn't going to use any rare parts but substitutes. I planned to use a CMOS gate, diodes, and resistors but I ended up having most of the rare parts in my inventory so didn't do this modification on my 208.

Dave
Don T
davebr wrote:
Don T wrote:
I have some news for people that may be having trouble sourcing a rare part, or are just too cheap to want to spend $4 a pop for them...

...I'm talking about the MC846P chips that do the wave folding work on Card 9. Tonight while I was digging around looking for the temperature probe that came with my DMM, I found a pair of old DM7400 chips, which is a quad NAND gate with the same pinout as the MC846P. It is, of course, a TTL chip instead of a DTL chip like the MC846P. I had been thinking about the possibility of swapping them awhile actually, so after finding the long-lost temperature probe, I got bored and...

...I'll be damned, it worked!. In fact, I found no noticeable difference in the range of the Timbre control, or the tone. In other words, to my ears they sounded identical (And for those that don't know me well, I've made most of my adult income either using my ears, or by teaching younger musicians how to use theirs). Even played back through an NAD amplifier and a pair of these, they still sounded identical:

P.S. - No, I have not yet tried it with any other variety of 7400 (yet).


Note that the MC846 RTL part has an open collector with an internal pull up resistor. The outputs of two pairs of two gates are tied together forming a wired or configuration. Although your DM7400 part fits it is not an open collector part so the outputs tied together are fighting. I don't know what the output voltage level is when these gates fight but it is likely not a valid logic level. Note that you could add diodes and pullup resistors on the four outputs to turn this into a wired or configuration, but with the diodes you now don't meet Vil specs with TTL. You could do it with a CMOS gate and then the small diode drop doesn't matter.

I have used CMOS gates with diodes and pullup resistors on a 285 where Don also used the MC846 part in a similar configuration. When I decided to build my own personal 208 I wasn't going to use any rare parts but substitutes. I planned to use a CMOS gate, diodes, and resistors but I ended up having most of the rare parts in my inventory so didn't do this modification on my 208.

Dave


Interesting. As always, thanks for the info Dave. Given what you point out above, I would've expected a difference in tone/response, but I couldn't hear any. Maybe I'll put the scope on it and look at it that way. Perhaps logic levels don't matter much in this case since the chip is processing an analog signal? I mean, on the scope, as the wave folds, you see smaller sine waves superimposed on the fundamental that increase amplitude and number gradually as more CV is applied. If it was all about logic levels, 1s and 0s, wouldn't the output appear as a staircase wave with a gradually increasing amount of steps? I once built a 2-transistor OR gate (in a circuit simulator) and when it was fed 2 sine waves at different frequencies the output was an analog signal...

...of course, it is late here, and I could be way off base in my thinking. I will defer to your judgement/thoughts on this.

Funny you mention CMOS, as I was tempted earlier to try this with a 4011, and switching the necessary pins. I'd be interested to see how you rigged the CMOS chip in place of the MC846P. Sent you a PM, by the way.

For everyone else, maybe the 7400 wasn't such a good idea after all...
davebr
Don T wrote:
Interesting. As always, thanks for the info Dave. Given what you point out above, I would've expected a difference in tone/response, but I couldn't hear any. Maybe I'll put the scope on it and look at it that way. Perhaps logic levels don't matter much in this case since the chip is processing an analog signal? I mean, on the scope, as the wave folds, you see smaller sine waves superimposed on the fundamental that increase amplitude and number gradually as more CV is applied. If it was all about logic levels, 1s and 0s, wouldn't the output appear as a staircase wave with a gradually increasing amount of steps? I once built a 2-transistor OR gate (in a circuit simulator) and when it was fed 2 sine waves at different frequencies the output was an analog signal...

...of course, it is late here, and I could be way off base in my thinking. I will defer to your judgment/thoughts on this.

Funny you mention CMOS, as I was tempted earlier to try this with a 4011, and switching the necessary pins. I'd be interested to see how you rigged the CMOS chip in place of the MC846P. Sent you a PM, by the way.

For everyone else, maybe the 7400 wasn't such a good idea after all...

I have never taken the time to determine exactly what those chips are doing. I believe they are controlling the direction of the integrator for the second CO. They are driven by comparators at TTL levels. It may be that the two outputs fighting still act as a wired or depending on what the voltage level is so it could still work. I don't know the long term implications for reliability for a chip wired as such. There are open collector TTL gates but I have not looked for while and didn't find any with the same footprint. I keep thinking of taking a deeper dive into card 9 but never seem to have the time.

Dave
Don T
davebr wrote:
Don T wrote:
Interesting. As always, thanks for the info Dave. Given what you point out above, I would've expected a difference in tone/response, but I couldn't hear any. Maybe I'll put the scope on it and look at it that way. Perhaps logic levels don't matter much in this case since the chip is processing an analog signal? I mean, on the scope, as the wave folds, you see smaller sine waves superimposed on the fundamental that increase amplitude and number gradually as more CV is applied. If it was all about logic levels, 1s and 0s, wouldn't the output appear as a staircase wave with a gradually increasing amount of steps? I once built a 2-transistor OR gate (in a circuit simulator) and when it was fed 2 sine waves at different frequencies the output was an analog signal...

...of course, it is late here, and I could be way off base in my thinking. I will defer to your judgment/thoughts on this.

Funny you mention CMOS, as I was tempted earlier to try this with a 4011, and switching the necessary pins. I'd be interested to see how you rigged the CMOS chip in place of the MC846P. Sent you a PM, by the way.

For everyone else, maybe the 7400 wasn't such a good idea after all...

I have never taken the time to determine exactly what those chips are doing. I believe they are controlling the direction of the integrator for the second CO. They are driven by comparators at TTL levels. It may be that the two outputs fighting still act as a wired or depending on what the voltage level is so it could still work. I don't know the long term implications for reliability for a chip wired as such. There are open collector TTL gates but I have not looked for while and didn't find any with the same footprint. I keep thinking of taking a deeper dive into card 9 but never seem to have the time.

Dave


I cannot even begin to wrap my head around that particular wavefolder. The rectifier type I can sort of understand, but the eight NAND gate matrix, well, that just forms a pretty geometric pattern to my eyes, and that's it! cool
I think I'll keep playing with this, and check for things like excessive heat, as well as any changes in the rest of the module's performance/sound. I'll definitely get the scope out and compare MC846P vs. 7400. Then, if I can find a place where the cats can't get to it, I'll let it run with 7400s for 24Hrs. and see if any kind of meltdown or magic smoke occurs. So far, I've only run it for 30 minutes or so with 7400s.
davebr
Don T wrote:
davebr wrote:
Don T wrote:
Interesting. As always, thanks for the info Dave. Given what you point out above, I would've expected a difference in tone/response, but I couldn't hear any. Maybe I'll put the scope on it and look at it that way. Perhaps logic levels don't matter much in this case since the chip is processing an analog signal? I mean, on the scope, as the wave folds, you see smaller sine waves superimposed on the fundamental that increase amplitude and number gradually as more CV is applied. If it was all about logic levels, 1s and 0s, wouldn't the output appear as a staircase wave with a gradually increasing amount of steps? I once built a 2-transistor OR gate (in a circuit simulator) and when it was fed 2 sine waves at different frequencies the output was an analog signal...

...of course, it is late here, and I could be way off base in my thinking. I will defer to your judgment/thoughts on this.

Funny you mention CMOS, as I was tempted earlier to try this with a 4011, and switching the necessary pins. I'd be interested to see how you rigged the CMOS chip in place of the MC846P. Sent you a PM, by the way.

For everyone else, maybe the 7400 wasn't such a good idea after all...

I have never taken the time to determine exactly what those chips are doing. I believe they are controlling the direction of the integrator for the second CO. They are driven by comparators at TTL levels. It may be that the two outputs fighting still act as a wired or depending on what the voltage level is so it could still work. I don't know the long term implications for reliability for a chip wired as such. There are open collector TTL gates but I have not looked for while and didn't find any with the same footprint. I keep thinking of taking a deeper dive into card 9 but never seem to have the time.

Dave


I cannot even begin to wrap my head around that particular wavefolder. The rectifier type I can sort of understand, but the eight NAND gate matrix, well, that just forms a pretty geometric pattern to my eyes, and that's it! cool
I think I'll keep playing with this, and check for things like excessive heat, as well as any changes in the rest of the module's performance/sound. I'll definitely get the scope out and compare MC846P vs. 7400. Then, if I can find a place where the cats can't get to it, I'll let it run with 7400s for 24Hrs. and see if any kind of meltdown or magic smoke occurs. So far, I've only run it for 30 minutes or so with 7400s.

You won't have a meltdown. It's just that one TTL gate could be trying to pullup and the other down so they fight. It pulls a bit more current and the resulting voltage could not be in the Vil or Vih range. The TTL gate downstream will have to decide what to do with that voltage and will most likely output a valid 0 or 1.

I haven't looked at that circuit for some time, but the way the timbre works is running two parallel COs that have to track. One then modulates the other. The two VCOs have to track so I think the square wave from one is used to reset the other. It's a bizarre circuit and was completely redone in the later version to adding a wavefolder. It is also used in the 285 and I have never taken the time to really understand it completely.

In doing a quick check, a 74LS03 is an open collector NAND gate. I don't know why I didn't find that before. That should work if you add external pullup resistors. You would need to only add 5 pullup resistors. There is no need to duplicate pullup resistors on the outputs that are tied together. Add resistors on IC1 pins 3, 8, and 11 and on IC2 pins 3 and 6. The resistors can be soldered on the top of the ICs and connect to pin 14. Something like a 2K4 should work.

Dave
Don T
davebr wrote:
Don T wrote:


I cannot even begin to wrap my head around that particular wavefolder. The rectifier type I can sort of understand, but the eight NAND gate matrix, well, that just forms a pretty geometric pattern to my eyes, and that's it! cool
I think I'll keep playing with this, and check for things like excessive heat, as well as any changes in the rest of the module's performance/sound. I'll definitely get the scope out and compare MC846P vs. 7400. Then, if I can find a place where the cats can't get to it, I'll let it run with 7400s for 24Hrs. and see if any kind of meltdown or magic smoke occurs. So far, I've only run it for 30 minutes or so with 7400s.

You won't have a meltdown. It's just that one TTL gate could be trying to pullup and the other down so they fight. It pulls a bit more current and the resulting voltage could not be in the Vil or Vih range. The TTL gate downstream will have to decide what to do with that voltage and will most likely output a valid 0 or 1.

I haven't looked at that circuit for some time, but the way the timbre works is running two parallel COs that have to track. One then modulates the other. The two VCOs have to track so I think the square wave from one is used to reset the other. It's a bizarre circuit and was completely redone in the later version to adding a wavefolder. It is also used in the 285 and I have never taken the time to really understand it completely.

In doing a quick check, a 74LS03 is an open collector NAND gate. I don't know why I didn't find that before. That should work if you add external pullup resistors. You would need to only add 5 pullup resistors. There is no need to duplicate pullup resistors on the outputs that are tied together. Add resistors on IC1 pins 3, 8, and 11 and on IC2 pins 3 and 6. The resistors can be soldered on the top of the ICs and connect to pin 14. Something like a 2K4 should work.

Dave


This gets more interesting! I definitely have a project to work on now. Thanks for this most useful info Dave!

Im glad to know that there'll probably not be a meltdown, but I'll still probably put everything through the check-and-burn-in process anyway. In all my years doing repairs, I've seen some crazy stuff happen!
Dimitree
if I understand correctly, the problem is that we have 2 pairs of NAND gates outputs tied together.
So what if, using a CMOS 4011, you put a diode on each of those output and a pulldown resistor for each join?
So the outputs are OR-ed and should not fight. Or maybe they need to be AND-ed?
Dimitree
this is what I mean,
what do you think?
Don T
Dimitree wrote:
Or maybe they need to be AND-ed?


Somehow, given the context, that sentence shorted out a few of my neurons... nuts
davebr
Dimitree wrote:
if I understand correctly, the problem is that we have 2 pairs of NAND gates outputs tied together.
So what if, using a CMOS 4011, you put a diode on each of those output and a pulldown resistor for each join?
So the outputs are OR-ed and should not fight. Or maybe they need to be AND-ed?

The work I did on the 285 used a CD4011 and I isolated the four outputs with diodes and a 10K pullup where the two diodes connect, so just two pullups. Yes, that would work. For a wired or you want the cathode connected to the gate and the pullup on the anode. This way the gate can pull low but not high. They both have to be high for the pullup to go high.

For positive logic it is wired and, for negative logic it is wired or. Technically, the RS flip flop inputs are negative logic so it is a wired "or"

Dave
davebr
Dimitree wrote:
this is what I mean,
what do you think?

Flip the diodes around. They need to pull low but float high.

Dave
Dimitree
davebr wrote:
Dimitree wrote:
this is what I mean,
what do you think?

Flip the diodes around. They need to pull low but float high.

Dave


cool! thanks!
and based on your prev. reply, I guess I need the resistors to be pullup, and not pulldown as I drawn, am I right?
davebr
Dimitree wrote:
davebr wrote:
Dimitree wrote:
this is what I mean,
what do you think?

Flip the diodes around. They need to pull low but float high.

Dave


cool! thanks!
and based on your prev. reply, I guess I need the resistors to be pullup, and not pulldown as I drawn, am I right?

I missed that. Yes, pullup to +5V. However, I believe a 74LS03 will work fine with 5 pullups on the two chips. That is a more direct plug-in solution.

Dave
Don T
davebr wrote:
However, I believe a 74LS03 will work fine with 5 pullups on the two chips. That is a more direct plug-in solution.

Dave


I've added a few 74LS03 to my next Mouser order, will report results here as soon as available!
Dimitree
davebr wrote:
However, I believe a 74LS03 will work fine with 5 pullups on the two chips. That is a more direct plug-in solution.

Dave


thanks Dave!
do you know what's the purpose of the pair of diodes on each of the 3 comparators in front of the NANDs network?
I see a pullup resistor to +5V on each output of the comparator, I guess they need it so the output is always 0V to 5V (since the NANDs want 0V to 5V), but why the diodes?
Don T
Dimitree wrote:

do you know what's the purpose of the pair of diodes on each of the 3 comparators in front of the NANDs network?
I see a pullup resistor to +5V on each output of the comparator, I guess they need it so the output is always 0V to 5V (since the NANDs want 0V to 5V), but why the diodes?


I would imagine the purpose is to keep the comparators centered between +5V and Ground, so that the output of the comparators can have a full 5V p-p voltage swing without any DC offset putting the range of the waveform out of the 0-5V range needed by the NANDs. That's just a guess though, I could be wrong. It seems like a way to get around not having a rail-to-rail comparator and powering it off the 5V line. Like I said, just a guess...
davebr
Don T wrote:
Dimitree wrote:

do you know what's the purpose of the pair of diodes on each of the 3 comparators in front of the NANDs network?
I see a pullup resistor to +5V on each output of the comparator, I guess they need it so the output is always 0V to 5V (since the NANDs want 0V to 5V), but why the diodes?


I would imagine the purpose is to keep the comparators centered between +5V and Ground, so that the output of the comparators can have a full 5V p-p voltage swing without any DC offset putting the range of the waveform out of the 0-5V range needed by the NANDs. That's just a guess though, I could be wrong. It seems like a way to get around not having a rail-to-rail comparator and powering it off the 5V line. Like I said, just a guess...

Correct. This is why you can't substitute a more modern op-amp like the TL071 as it would swing rail to rail. If you do swing rail to rail one typically adds a series resistor (like R29 and R29) to limit the current and then add diodes to +5 and ground. Don didn't add the diodes but often added a current limit resistor and relied on the internal of the chip for the clamp. I never liked that approach.

Dave
Dimitree
good to know! btw those 3x LM301 are used as simple comparator rights? to me it looks so, since none of them have resistors used in the feedback loop. But one of them (IC7) has got a capacitor (C7) in the loop.
Does this means that there is some feedback and it is not working as comparator?
Or their output is still 0V OR 5V, with no other in-between states?
Don T
Sorry it's been awhile, life sometimes intervenes...

The only card I haven't presented yet, Card 6:



Card 6 builds up and runs as expected with no surprises. On this card, the 2N4339 JFET need not be selected, so you have a place to use at least one of the ones that weren't suitable for the Sine wave shaper! cool

A couple of notes on this particular card though -

The uA726 has been replaced by yet another prototype board designed by jhulk. Some part values have been tweaked since the last one I built to improve performance. These are now in production and available as bare PCBs. Also in the photo is one I built on a factory-made board to write an updated build doc. These boards are currently available at Modular Addict, and I believe will be carried elsewhere soon.

The other item of note on this board are the Molex connectors. The part number called for in the BOM has recently been marked "end of life". There are still many in stock at various places, but I went ahead and searched for an alternative. The part used on this board is Molex part number 09-48-2061.

http://www.mouser.com/Search/ProductDetail.aspx?R=09-48-2061virtualkey 53810000virtualkey538-09-48-2061

I found the part to be a suitable alternative. The main differences between this part and the previously called for part are: The new part has plated brass contacts as opposed to plated phosphor-broze contacts, and the housing is slightly different, as it is molded to guide the pins into the connector instead of being wide open. I find this new part easier to plug in because of this.

Here's a close up showing the difference. The old part is the translucent one, while the new one is the solid white one:



I hope to get the motherboard going soon!
durwin
Very green to this party - where can I source the board/panel/kit from? we're not worthy
captnapalm
durwin wrote:
Very green to this party - where can I source the board/panel/kit from? we're not worthy


https://electricmusicstore.com/products/stored-program-sound-source-mo del-208-rev2-1

http://siddarthianinnovations.bigcartel.com/product/208-front-panel
Sammus
With Excelitas virtually unobtainable now (I have 4 for the LPG at least!) I've been looking for alternatives.

There is the Xvive 5C1 recommended by Don T, but I've also found the Macron series on smallbear. Has anyone compared to Xvive for Excelitas?

Cheers
livefreela
Sammus wrote:
With Excelitas virtually unobtainable now (I have 4 for the LPG at least!) I've been looking for alternatives.

There is the Xvive 5C1 recommended by Don T, but I've also found the Macron series on smallbear. Has anyone compared to Xvive for Excelitas?

Cheers


the short answer, yes, xvive 5c3s can work - my response to another wiggler in a different vactrol-related thread:

i’m one of the opinion (admittedly probably the minority) that the xvive devices can be used with splendid results in buchla modules - however, there is a caveat… a sizeable percentage of them are bullshit.

when i was building my 208r rev 2 I ordered a lot of 30 or so xvive 5c3s and put them on a test rig similar to the one dave brown details on his website. about 25 of them responded very similarly to the excelitas samples I had on hand. however, of the remainder, a few measured almost 2x the on-resistance of the excelitas devices, and the others had this really strange delayed off - taking almost 1.5 to 2 seconds to close after current was applied. were one to plug these into the lpg circuit in the 208 or a 292 i have no doubt they’d report the “not-quite-right” behavior some experienced buchla builders have reported with the xvives. no “snap”, sloppy response, etc...

all that said - I took the of speediest samples (notated during testing), paired them appropriately and set them aside for the “mission-critical” parts of the 208, namely the lgs and the balanced-modulator. I can’t speak to the “authenticity” of my build as I don’t have much experience with genuine buchla, but i’m really happy with how the instrument turned out. Gryphon, I think you’d be fine using the xvives, just make sure to buy a few extra to account for the wonky ones & be sure to test then before installing"
masterofstuff124
can you link to Dave Browns test rig details? I combed through his website(which is amazing btw) and couldn't find it. I am planning on buying a bunch of 5c3/c1 s and would like to test before putting into modules.

http://modularsynthesis.com

thanks
cygmu
http://www.modularsynthesis.com/roman/buchla292c/292qlpg.htm

Quote:

I matched the vactrols so the channels would be near equal. I powered the vactrol LED from +15 volts through a 2K2 resistor and measured the output resistance. The resistance slightly changes as the vactrol warms with the LED current so I used the initial resistance and selected four that were close in value.
we_squirm
Slightly off topic but has anyone heard from Roman recently? I ordered a 208 V2.1 and 218 PCB set three weeks ago and haven't even gotten a shipping notice. Dying to start my build. I have all the other parts ready to go....
livefreela
this is what i did. i just flicked the power on for a second or so and quickly off - the strange, anomalous xvives have a very pronounced / extended decay upon powering off.

cygmu wrote:
http://www.modularsynthesis.com/roman/buchla292c/292qlpg.htm

Quote:

I matched the vactrols so the channels would be near equal. I powered the vactrol LED from +15 volts through a 2K2 resistor and measured the output resistance. The resistance slightly changes as the vactrol warms with the LED current so I used the initial resistance and selected four that were close in value.
benadryl
I want to build one of these more than anything but have no DIY experience very frustrating

Starting out with a bastro quattro figaro kit and I've learned a lot so far. Hopefully I'll be able to work my way up to something like this soon.
davebr
benadryl wrote:
I want to build one of these more than anything but have no DIY experience very frustrating

Starting out with a bastro quattro figaro kit and I've learned a lot so far. Hopefully I'll be able to work my way up to something like this soon.

Practice up very well. The 208 is in no way a beginner's kit. I get a lot of emails of 208s that once assembled don't operate. The ones that we can't get running via email sometimes get sent to me and I have been sent a lot of them. I have two of them on the bench right now.

There is no silk screen and the resistor lead spacing is different between 1% and 5%. It is easy to put a resistor or capacitor into a feed through hole instead of the pad. Diodes can go in backwards. If you don't solder the Molex connectors on EXTREMELY tight to the PCB then it is a bear getting them to plug in because they flex every which way. With no solder mask it is easy to get bridges. That is what I usually find on the cards.

The motherboard has a lot of components and a lot of parallel runs. Solder bridges on the motherboard are a real problem as that is a multi-hour project to separate, repair, and reassemble. There are a lot of LEDs which need to be aligned. I solder mine in place once assembled, but when you have to tear down, you can't move them at all or they won't realign. People get them in backwards and the legs can bend and touch.

One of the biggest issues I see is poor assembly. The switches need the backing nut. Otherwise when you tighten the top nut you just smash the panel down and then it will never stay tight. Wires don't need an extra 1/4" of insulation removed when soldered to the PCB, especially the power leads. Any shielded wire needs to be small and flexible. It doesn't help to mount the reverb on springs and then use a stiff coax that holds it firm or worse rubs on the springs.

The program extender card doesn't need solder covering the entire pad. It need to be straight and clean so it doesn't short when inserted. I've spent a lot of time chasing shorts that were from misalignment. The first thing I do now is remove that card before troubleshooting.

Do NOT save money by buying cheap sockets or switches. These are the most unreliable part of the module and you want quality components. Replacing a broken switch is not much fun. It's even worse if the banana wires are soldered straight with no slack. With slack you can sometimes lift the panel up high enough to slide a new switch in.

It is not unusual for me to put up to 8 hours in doing a repair, full verification, and calibration on a 208. It is not a beginners project but with enough time they all work and work well.

Just my experience.

Dave
jersupereq
Has anyone built this with Roman's uA726 replacement boards? I'm wondering if there's any bom for them.
davebr
jersupereq wrote:
Has anyone built this with Roman's uA726 replacement boards? I'm wondering if there's any bom for them.

I don't know if this is Roman's uA726 board or not but the 208 I have on the bench for repairs has these uA206 replacements. They are just a matched SMT pair and a tempco. Note the tempco is actually wired between the two bases so could be wired to the daughter board instead of the card.

For my own I simply used tape and reel 2N3904s which are matched good enough and epoxied them together and then epoxied a tempco on top. Details of that with measurements are on my Buchla 208 V2 page.

Dave



tarandfeathers
Definitely agree. Building isn't an especially cheap way of getting a music easel. It's a good project if you really enjoy planning, processes, electronic assembly and troubleshooting. I had a relatively trouble free build, did not make any mistakes and did all of the necessary modifications as part of my build but I still have a couple of outstanding bugs, and had to make numerous modifications of my own to get it operating how (I feel) it should. I suspect that many people "complete" a build but leave it with bugs/not properly calibrated because they either don't know/care it isn't working properly, or don't have the means to find the problems they do have (or more likely both).

I really enjoyed doing it but it would have been painful if I did not have a fancy PCB assembly jig, good desoldering station, a couple of good bench power supplies so that I could test with confidence that any problems were not power related, and a good oscilloscope. In fact, working on understanding the envelope generator I found that the four channels of my scope were not really enough and I wish I could justify the money for the logic analyser option at the moment. Even without that, that would be a heavy investment in equipment for someone who isn't already doing a lot of electronics.

Not saying don't do it. Just bear in mind that no build is problem free and there are obstacles like none of the available schematics exactly matching the RF version, interactions between the various cards meaning a problem with the complex oscillator (for example) might actually be on card 5, 7, 8, 9 or 10, or a sequencer issue might actually turn out to be on card 3. You need to be able to follow the diagrams and understand what's going on to hunt these things down so consider your level of experience before dropping a lot of money on something that might end up being an (admittedly very pretty) paperweight.

davebr wrote:
benadryl wrote:
I want to build one of these more than anything but have no DIY experience :bang:

Starting out with a bastro quattro figaro kit and I've learned a lot so far. Hopefully I'll be able to work my way up to something like this soon.

Practice up very well. The 208 is in no way a beginner's kit. I get a lot of emails of 208s that once assembled don't operate. The ones that we can't get running via email sometimes get sent to me and I have been sent a lot of them. I have two of them on the bench right now.

There is no silk screen and the resistor lead spacing is different between 1% and 5%. It is easy to put a resistor or capacitor into a feed through hole instead of the pad. Diodes can go in backwards. If you don't solder the Molex connectors on EXTREMELY tight to the PCB then it is a bear getting them to plug in because they flex every which way. With no solder mask it is easy to get bridges. That is what I usually find on the cards.

The motherboard has a lot of components and a lot of parallel runs. Solder bridges on the motherboard are a real problem as that is a multi-hour project to separate, repair, and reassemble. There are a lot of LEDs which need to be aligned. I solder mine in place once assembled, but when you have to tear down, you can't move them at all or they won't realign. People get them in backwards and the legs can bend and touch.

One of the biggest issues I see is poor assembly. The switches need the backing nut. Otherwise when you tighten the top nut you just smash the panel down and then it will never stay tight. Wires don't need an extra 1/4" of insulation removed when soldered to the PCB, especially the power leads. Any shielded wire needs to be small and flexible. It doesn't help to mount the reverb on springs and then use a stiff coax that holds it firm or worse rubs on the springs.

The program extender card doesn't need solder covering the entire pad. It need to be straight and clean so it doesn't short when inserted. I've spent a lot of time chasing shorts that were from misalignment. The first thing I do now is remove that card before troubleshooting.

Do NOT save money by buying cheap sockets or switches. These are the most unreliable part of the module and you want quality components. Replacing a broken switch is not much fun. It's even worse if the banana wires are soldered straight with no slack. With slack you can sometimes lift the panel up high enough to slide a new switch in.

It is not unusual for me to put up to 8 hours in doing a repair, full verification, and calibration on a 208. It is not a beginners project but with enough time they all work and work well.

Just my experience.

Dave
Don T
tarandfeathers wrote:
Definitely agree. Building isn't an especially cheap way of getting a music easel. It's a good project if you really enjoy planning, processes, electronic assembly and troubleshooting. I had a relatively trouble free build, did not make any mistakes and did all of the necessary modifications as part of my build but I still have a couple of outstanding bugs, and had to make numerous modifications of my own to get it operating how (I feel) it should. I suspect that many people "complete" a build but leave it with bugs/not properly calibrated because they either don't know/care it isn't working properly, or don't have the means to find the problems they do have (or more likely both).

I really enjoyed doing it but it would have been painful if I did not have a fancy PCB assembly jig, good desoldering station, a couple of good bench power supplies so that I could test with confidence that any problems were not power related, and a good oscilloscope. In fact, working on understanding the envelope generator I found that the four channels of my scope were not really enough and I wish I could justify the money for the logic analyser option at the moment. Even without that, that would be a heavy investment in equipment for someone who isn't already doing a lot of electronics.

Not saying don't do it. Just bear in mind that no build is problem free and there are obstacles like none of the available schematics exactly matching the RF version, interactions between the various cards meaning a problem with the complex oscillator (for example) might actually be on card 5, 7, 8, 9 or 10, or a sequencer issue might actually turn out to be on card 3. You need to be able to follow the diagrams and understand what's going on to hunt these things down so consider your level of experience before dropping a lot of money on something that might end up being an (admittedly very pretty) paperweight.

davebr wrote:
benadryl wrote:
I want to build one of these more than anything but have no DIY experience very frustrating

Starting out with a bastro quattro figaro kit and I've learned a lot so far. Hopefully I'll be able to work my way up to something like this soon.

Practice up very well. The 208 is in no way a beginner's kit. I get a lot of emails of 208s that once assembled don't operate. The ones that we can't get running via email sometimes get sent to me and I have been sent a lot of them. I have two of them on the bench right now.

There is no silk screen and the resistor lead spacing is different between 1% and 5%. It is easy to put a resistor or capacitor into a feed through hole instead of the pad. Diodes can go in backwards. If you don't solder the Molex connectors on EXTREMELY tight to the PCB then it is a bear getting them to plug in because they flex every which way. With no solder mask it is easy to get bridges. That is what I usually find on the cards.

The motherboard has a lot of components and a lot of parallel runs. Solder bridges on the motherboard are a real problem as that is a multi-hour project to separate, repair, and reassemble. There are a lot of LEDs which need to be aligned. I solder mine in place once assembled, but when you have to tear down, you can't move them at all or they won't realign. People get them in backwards and the legs can bend and touch.

One of the biggest issues I see is poor assembly. The switches need the backing nut. Otherwise when you tighten the top nut you just smash the panel down and then it will never stay tight. Wires don't need an extra 1/4" of insulation removed when soldered to the PCB, especially the power leads. Any shielded wire needs to be small and flexible. It doesn't help to mount the reverb on springs and then use a stiff coax that holds it firm or worse rubs on the springs.

The program extender card doesn't need solder covering the entire pad. It need to be straight and clean so it doesn't short when inserted. I've spent a lot of time chasing shorts that were from misalignment. The first thing I do now is remove that card before troubleshooting.

Do NOT save money by buying cheap sockets or switches. These are the most unreliable part of the module and you want quality components. Replacing a broken switch is not much fun. It's even worse if the banana wires are soldered straight with no slack. With slack you can sometimes lift the panel up high enough to slide a new switch in.

It is not unusual for me to put up to 8 hours in doing a repair, full verification, and calibration on a 208. It is not a beginners project but with enough time they all work and work well.

Just my experience.

Dave


Excellent advice from both davebr and tarandfeathers! Perhaps I should update the first post with a list of not-so-obvious tools needed, such as an oscilloscope, and/or a frequency counter or tuner?

I promise I'll get to the motherboard soon, just need to figure out what sliders I want to use.
we_squirm
Where did y'all source the coloured caps for the sliders? I found Mammoth has ones for the switches but can't find the slider guys anywhere!
Don T
we_squirm wrote:
Where did y'all source the coloured caps for the sliders? I found Mammoth has ones for the switches but can't find the slider guys anywhere!


They are one and the same! Seriously. Warm the caps up (I heat mine up in a strainer over boiling water) and slide them down on top of the sliders.
auxren
What is the best way to get individual oscillator outputs from the 208 to interface with the rest of my Buchla system? I saw that there is no audio broken out to the program card.
I'm thinking of replacing the to/from prog banana jacks with tinijax with vco 1 and vco2 out.
davebr
auxren wrote:
What is the best way to get individual oscillator outputs from the 208 to interface with the rest of my Buchla system? I saw that there is no audio broken out to the program card.
I'm thinking of replacing the to/from prog banana jacks with tinijax with vco 1 and vco2 out.

The MO output is on the banana. It is just level shifted to be unipolar. Personally, I would change one of the signal output jacks to stereo and put both the MO and CO on that. Then you just need a splitter cable to separate the stereo to two mono. That way you don't eliminate any functionality and there are no holes drilled.

Dave
auxren
davebr wrote:
auxren wrote:
What is the best way to get individual oscillator outputs from the 208 to interface with the rest of my Buchla system? I saw that there is no audio broken out to the program card.
I'm thinking of replacing the to/from prog banana jacks with tinijax with vco 1 and vco2 out.

The MO output is on the banana. It is just level shifted to be unipolar. Personally, I would change one of the signal output jacks to stereo and put both the MO and CO on that. Then you just need a splitter cable to separate the stereo to two mono. That way you don't eliminate any functionality and there are no holes drilled.

Dave


I like that solution! I'll scope it out. Thanks Dave
we_squirm
Don T wrote:
we_squirm wrote:
Where did y'all source the coloured caps for the sliders? I found Mammoth has ones for the switches but can't find the slider guys anywhere!


They are one and the same! Seriously. Warm the caps up (I heat mine up in a strainer over boiling water) and slide them down on top of the sliders.


Thank you!
Sammus
I have a couple of questions about caps on the BOM:

1) There's a couple of 5% ceramic caps on card 12:

140-50S5-101J-RC
140-50S5-471J-RC

that are marked obsolete on mouser, and there don't seem to be any substitutes with the same characteristics (5% tol, 5mm lead spacing, ceramic disc).

How important are those characteristics? Can I just replace them with any ceramic disc or mlcc 100pf and 470pf?

2) there was recently a post on the JML synth page about some errors in the 208r BOM without many specifics:
Quote:
their's some wrong diodes that are for making the 12volts +/- to 7.5volts the diodes specified makes the voltage to high and it fries the chip. Also he has stated 10000pf caps code# 104j but they are supposed to be 910pf code# 911j


Are these diodes the known 7.5v zeners mentioned in this thread that are in the v2.1 BOM? And also what about the 10,000pf vs 910pf caps??

Thanks for any help!
tarandfeathers
Sammus wrote:
I have a couple of questions about caps on the BOM:

1) There's a couple of 5% ceramic caps on card 12:

140-50S5-101J-RC
140-50S5-471J-RC

that are marked obsolete on mouser, and there don't seem to be any substitutes with the same characteristics (5% tol, 5mm lead spacing, ceramic disc).

How important are those characteristics? Can I just replace them with any ceramic disc or mlcc 100pf and 470pf?


Yes, I did my whole build with TDK 5% C0G ceramics, it's not important, just the value and voltage tolerance, but ceramics with less than 40/50V capability are unusual and the biggest voltage difference in the 208 is 30V.

Quote:
2) there was recently a post on the JML synth page about some errors in the 208r BOM without many specifics:
Quote:
their's some wrong diodes that are for making the 12volts +/- to 7.5volts the diodes specified makes the voltage to high and it fries the chip. Also he has stated 10000pf caps code# 104j but they are supposed to be 910pf code# 911j


Are these diodes the known 7.5v zeners mentioned in this thread that are in the v2.1 BOM? And also what about the 10,000pf vs 910pf caps??

Thanks for any help!


This is a reference to the previous V2 BOM. If you are building from the V2.1 BOM then the correct zeners are specified.

I'm not aware of anywhere that 10,000pF caps were specified in place of 910pF, but 1000pF are used throughout wherever 910pF were used in the original. For some reason Don Buchla barely ever used 1000pF caps, I suspect he must have got a deal on thousands and thousands of 910pF caps in the late 60s/early 70s and spent the next 10 years trying to use them up, haha. At any rate, it's not important. None of these are used in critical timing applications so 1000pF is more than close enough.
Sammus
Awesome thanks.
Don T
tarandfeathers wrote:
For some reason Don Buchla barely ever used 1000pF caps, I suspect he must have got a deal on thousands and thousands of 910pF caps in the late 60s/early 70s and spent the next 10 years trying to use them up, haha. At any rate, it's not important. None of these are used in critical timing applications so 1000pF is more than close enough.


There are a couple 910pf caps in the filter section of the lo pass gates (Cards 10 and 11), and I usually make sure I use 910pf in those positions at least.
we_squirm
How's it going with the Motherboard? It's the only card we haven't seen finished, correct?
Don T
Don T wrote:
davebr wrote:
However, I believe a 74LS03 will work fine with 5 pullups on the two chips. That is a more direct plug-in solution.

Dave


I've added a few 74LS03 to my next Mouser order, will report results here as soon as available!


Sorry, meant to post results earlier:



Thanks to davebr for his advice on this. Yes, the above works. It works incredibly well in fact. The sound is indistinguishable from the original chip, and probing around the circuit in various points with the scope while sweeping the Timbre control also confirms that performance is identical to the original chip. So, if you can't find MC846P, give 74LS03 a try! I used 2.7K pull up resistors.
we_squirm
Don T wrote:
Some progress, and perhaps a solution to a common problem should anyone else want to confirm.

I have worked on many different pieces of gear, and have noticed almost all of them that use CMOS chips have a decoupling cap across the Vdd and Vss (or ground) pins of most, if not all the CMOS chips. The original 208, as well as the 208r V2 and V2.1, have NONE. Most of the stability issues in the 208r are CMOS-chip-related, and I happened to run across a deal on these really nice machined-pin sockets that have decoupling caps built-in. I figured it may be worth a try, and at the very least it should do no harm...

Since I'm not an expert (at all) on CMOS-related things, I ran the idea by davebr. He gave me a thorough and educational response (Dave, feel free to jump in, or I can share your response here if you'd like) that basically said it may be a good idea in the sequencer, but perhaps putting them on every CMOS chip would be overkill. He mentioned that he tends to put one decoupling cap for every three CMOS chips. Dave also cautioned to make sure that any additional caps would not add enough capacitance to allow a charge to be stored in a voltage regulated circuit large enough that it would reverse-bias a voltage regulator, unless the regulator has protection diodes installed. Think of it as a "back flow" if you will, especially when powering down.

So, with basically a "go for it", I installed the sockets on my sequencer board. The decoupling cap can be removed without too much trouble, so I pulled it out of the socket for the LM3900:



In my previous post, I mentioned the trouble I had been having with my first 208's sequencer LEDs, and the solution, which involved replacing what I assumed was a faulty CD4009, which is the LED driver for this circuit. As an experiment, I placed the new 4009 in one of those decoupled sockets to see if there would be a result, plus you can see above that I didn't use sockets at all on my first build, which tends to slow things down a bit if you need to replace a chip...

Here's that part you've been waiting patiently for, hoping I would shut up and just get on with it:

Before installing the decoupling socket, my first sequencer card displayed the common behavior of only doing 2 steps with the Stages switch set to 3. It would do 4 and 5 steps normally, but not 3. Well, after installing that socket with the decoupling cap, and no other modifications done, that same sequencer card now reliably switches between 3, 4, and 5 stages as designed! nanners

The new, blue sequencer card, which you can see above has decoupling caps everywhere except the LM3900, and no other modifications, also switches reliably between 3, 4, and 5 steps as designed.

Being a firm believer in "Correlation Does Not Imply Causality" (unless confirmed), I am not going to declare the decoupling solution as the fix for the 2, 4, 5 step sequencer bug until someone else confirms. All one needs to do is solder a 0.1uf cap (ceramic will do nicely) on the back of IC9 on their sequencer (Card 1) between pins 8 and 16. Please share your results here!

Right now, all I'm going to tell you guys is that I have two otherwise-unmodified sequencers that behave as intended!



And yes, the sockets just happened to be blue! nanners


Just to clarify as this is a bit new to me, which legs on the IC socket do you solder the decoupling cap to? and as for value (again just to clarify as I prefer to over state it instead of making a mistake) you're using a 0.1uf monolytic cap?
Don T
we_squirm wrote:
Don T wrote:
Some progress, and perhaps a solution to a common problem should anyone else want to confirm.

I have worked on many different pieces of gear, and have noticed almost all of them that use CMOS chips have a decoupling cap across the Vdd and Vss (or ground) pins of most, if not all the CMOS chips. The original 208, as well as the 208r V2 and V2.1, have NONE. Most of the stability issues in the 208r are CMOS-chip-related, and I happened to run across a deal on these really nice machined-pin sockets that have decoupling caps built-in. I figured it may be worth a try, and at the very least it should do no harm...



Just to clarify as this is a bit new to me, which legs on the IC socket do you solder the decoupling cap to? and as for value (again just to clarify as I prefer to over state it instead of making a mistake) you're using a 0.1uf monolytic cap?


Yes, a 0.1uf cap is used, and it is soldered across pins 7 and 14 of a 14-pin CMOS chip, and pins 8 and 16 of a 16-pin CMOS chip. Just the CMOS chips mind you, those marked CD40xx.
davebr
Don T wrote:
Yes, a 0.1uf cap is used, and it is soldered across pins 7 and 14 of a 14-pin CMOS chip, and pins 8 and 16 of a 16-pin CMOS chip. Just the CMOS chips mind you, those marked CD40xx.

I only solder decoupling capacitors across the CMOS parts on Card 1. I don't on any of the other cards. FYI.

Dave
Don T
davebr wrote:
Don T wrote:
Yes, a 0.1uf cap is used, and it is soldered across pins 7 and 14 of a 14-pin CMOS chip, and pins 8 and 16 of a 16-pin CMOS chip. Just the CMOS chips mind you, those marked CD40xx.

I only solder decoupling capacitors across the CMOS parts on Card 1. I don't on any of the other cards. FYI.

Dave


Yes, forgot to mention they don't ALL need decoupling caps. I added one to all of Card 1 as well, plus I did one CMOS chip per card, and only on the cards that had CMOS chips.

But, definitely do Card 1, I found that it stabilizes the sequencer and allows it to run as intended. When first built, mine had the common problem of running in 2, 4, or 5 steps only. If the switch was set for three stages it would only do two. With the decoupling caps added it works without a glitch.
cnicht
Can anyone tell me the dimensions of the 208r front panel please?

Thanks
captnapalm
cnicht wrote:
Can anyone tell me the dimensions of the 208r front panel please?

Thanks


It should be exactly 7" x 17"
cnicht
Thank you
Karma
hey guys!!! are there any alternative for the toggles switch? C&K are a way too expensive, i wonder if the mountain switch fits, like this http://www.mouser.fr/ProductDetail/Mountain-Switch/108-0044-EVX/?qs=%2 fha2pyFaduhRthU2YSVz8cwTjfhFolTuJcC8NxBJT50%3d for the spdt on off on or other reference
we_squirm
Where did y'all source your Accutronics 1bc2e reverb tank? The only link I found online was tube amp doctor, which is in Europe. I'm in Canada so something in North America would be great.
Sammus
we_squirm wrote:
Where did y'all source your Accutronics 1bc2e reverb tank? The only link I found online was tube amp doctor, which is in Europe. I'm in Canada so something in North America would be great.


The only place I found was to order directly from belton/accutronics in korea. I think it ends up being about 25usd delivered.
we_squirm
Sammus wrote:
we_squirm wrote:
Where did y'all source your Accutronics 1bc2e reverb tank? The only link I found online was tube amp doctor, which is in Europe. I'm in Canada so something in North America would be great.


The only place I found was to order directly from belton/accutronics in korea. I think it ends up being about 25usd delivered.


Awesome thanks! ALSO: where did y'all get the 22 x sliders for the mother board? Farrell (the place listed on the BOM) is out of stock and has an estimated delivery time of mid-November :S
Sammus
we_squirm wrote:
Sammus wrote:
we_squirm wrote:
Where did y'all source your Accutronics 1bc2e reverb tank? The only link I found online was tube amp doctor, which is in Europe. I'm in Canada so something in North America would be great.


The only place I found was to order directly from belton/accutronics in korea. I think it ends up being about 25usd delivered.


Awesome thanks! ALSO: where did y'all get the 22 x sliders for the mother board? Farrell (the place listed on the BOM) is out of stock and has an estimated delivery time of mid-November :S


I'm seeing around 4000 available?
http://uk.farnell.com/alps/rs4511150k/potentiometer-slide-50k/dp/11917 30
or

http://au.element14.com/alps/rs4511150k/potentiometer-slide-50k/dp/119 1730?CMP=i-55c5-00001622
we_squirm
Sammus wrote:
we_squirm wrote:
Sammus wrote:
we_squirm wrote:
Where did y'all source your Accutronics 1bc2e reverb tank? The only link I found online was tube amp doctor, which is in Europe. I'm in Canada so something in North America would be great.


The only place I found was to order directly from belton/accutronics in korea. I think it ends up being about 25usd delivered.


Awesome thanks! ALSO: where did y'all get the 22 x sliders for the mother board? Farrell (the place listed on the BOM) is out of stock and has an estimated delivery time of mid-November :S


I'm seeing around 4000 available?
http://uk.farnell.com/alps/rs4511150k/potentiometer-slide-50k/dp/11917 30
or


http://au.element14.com/alps/rs4511150k/potentiometer-slide-50k/dp/119 1730?CMP=i-55c5-00001622


Same, BUT when i placed the order they sent me an email saying expected delivery of November. Super weird.
davebr
Karma wrote:
hey guys!!! are there any alternative for the toggles switch? C&K are a way too expensive, i wonder if the mountain switch fits, like this http://www.mouser.fr/ProductDetail/Mountain-Switch/108-0044-EVX/?qs=%2 fha2pyFaduhRthU2YSVz8cwTjfhFolTuJcC8NxBJT50%3d for the spdt on off on or other reference

Let me offer my advice where none was asked. I do restorations at the vintageTEK museum and I restore vintage radios and music electronics as a part time business. The most unreliable parts in a 208 are the electromechanical parts - switches, potentiometers/sliders, and sockets. My advice is with the $$ you are going to put into it for parts and your time, you don't want a cheap switch to fail early. I have repaired 208s with crummy sockets and bad switches. The sockets are easy. Replacing a switch is not and you risk damaging the PCB without proper desoldering equipment. If you choose something other than the C&K, make sure they are very reliable.

Dave
we_squirm
For Card 9, when installing the DG200BA apparently you have to cut leg 7 off so the IC fits in the socket. There's a photo and description of that here: http://modularsynthesis.com/roman/buchla208v2/208spss.htm

My question, is the photo taken from the top down, or from the bottom up? It may seem silly but I just want to clarify before cutting a leg off. What is the orientation of the photo?
captnapalm
we_squirm wrote:
For Card 9, when installing the DG200BA apparently you have to cut leg 7 off so the IC fits in the socket. There's a photo and description of that here: http://modularsynthesis.com/roman/buchla208v2/208spss.htm

My question, is the photo taken from the top down, or from the bottom up? It may seem silly but I just want to clarify before cutting a leg off. What is the orientation of the photo?


the drawing is from the top down. so when you're looking down at the top of the IC, pin7 should be at about 4 o'clock.
davebr
we_squirm wrote:
For Card 9, when installing the DG200BA apparently you have to cut leg 7 off so the IC fits in the socket. There's a photo and description of that here: http://modularsynthesis.com/roman/buchla208v2/208spss.htm

My question, is the photo taken from the top down, or from the bottom up? It may seem silly but I just want to clarify before cutting a leg off. What is the orientation of the photo?

I should add that, but that is a top view. In the photo you can see where pad 7 is missing on the PCB (just barely). Instead of cutting you can always bend it out of the way, and then once verified, cut it off.

Dave
tarandfeathers
As some folks might be aware, there is a problem with the behaviour of the Music Easel envelope generator in sustained mode - at short settings of the duration slider, the envelope will not sustain indefinitely, but will slowly decay away. This is, as far as I can tell, a universal problem affecting all RF versions of the 208 (and most probably all original 70s modules as well, no one has yet confirmed whether or not the BEMI models do it but I wouldn't be surprised if they do.)

There were a couple of circuit revisions during the original lifespan of the 208 which were efforts to improve the behaviour of the circuit, but a proper fix was never implemented (I assume because the production numbers were so low, it was not considered worthwhile to spend much time on the issue).

This always bothered me (I quite specifically wanted to be able to set a very short envelope for very snappy playing but to also be able to hold notes for extended durations, tens of seconds up to minutes) so I recently spent a bunch of time working on understanding the function of the EG circuit, and coming up with a fix.

In essence, the envelope is based around an integrator, with some logic control switching on the different "stages" of the envelope to charge or discharge it. The duration stage is split into two parts, one that charges, and one that discharges, and, in sustain mode with a key held down, the second duration stage should oscillate on and off, keeping the integrator topped up with charge and holding the envelope high until the key is released, at which point the decay stage switches on. The problem is that whether or not the oscillation starts up depends on the duration slider setting on the front panel being long enough. Don Buchla added a "feedback" cap to the circuit to improve things but it does not fix the problem entirely, and can in fact lead to a level of instability where upon releasing a key the second duration stage and decay cycle back and forth forever and the envelope never closes.

I have prototyped a fix which completely resolves this problem. It involves some additional logic sniffing the status of all the envelope stages, and an electronic switch to add Don Buchlas feedback modification only at the appropriate time. I have done extensive testing with this and having the fix attached only fixes this behaviour and does not modify the timing or behaviour of the envelope in any other way.


Here's a scope trace of the envelope logic without the fix, and then one with it





I wanted an elegant way of implementing this, so I have designed a small board (32x29mm) which replaces IC3 and IC5 on the envelope card.



In order to make it fit, this board is all SMD with a double sided load, and since the pin headers that mate with the card must be precisely lined up to match the spacing of the footprints on the card, the best option seems to be to make it available as an assembled unit, ready to fit, so that's what I'm doing. Price will be £30/€35/$40US plus actual shipping cost from the UK to wherever you are. Boards will be shipped in an antistatic box/foam, inside a jiffy bag, and will include sockets to fit into the envelope card.

I have a final prototype arriving sometime in the next week so that I can check the spacing is perfect and then I will order a run and make them available. I will be setting up a website to deal with orders, feel free to let me know if you are interested but I will not be processing or keeping track of anything on here or through PMs. Unless I have more than 50 expressions of interest before I place the order, this will be a run of 50 and will be a one time run that will not be repeated.

Points of note:

*This will physically fit card 3 of 208r2 and 208r2.1 modules. It should fit original 70s 208s and another forthcoming easel clone being developed by jhulk and DonT but I have no way to check this, buy at your own risk.

*If you have used wiper type IC sockets on you card 3, the board will plug straight in, but this is a one time deal as the pin headers deform the wipers so you will have to replace the IC sockets if you want to go back to the unmodified behaviour. It will not fit in turned pin/machined IC sockets, but as noted will be supplied with suitable sockets to make it plug in/replaceable.

*It will not fit directly in the 208r1 or the BEMI easel and I will not be providing any support for doing so, but it should be possible to do if you know what you're doing. Again, buy at your own risk.

*Feel free to argue about whether it is "authentic" or not, but critically it produces the envelope behaviour I personally want, and it is my belief that this gets the envelope working as Don Buchla originally intended. It's my hope that having the boards fit straight into the IC3 and 5 positions makes the modification reversible enough for any cork sniffers out there, but you are most welcome not to buy if you feel that Don Buchla is an untouchable genius and nothing he did could possibly be improved twisted

*Apologies in advance for cross posting this on a couple of threads, I want to make sure it reaches the relevant parties.
we_squirm
n00b question, what gauge wire would everyone recommend for the power cable portion of the build, as well as the wire for the banana jacks?
we_squirm
we_squirm wrote:
n00b question, what gauge wire would everyone recommend for the power cable portion of the build, as well as the wire for the banana jacks?


plz delete. d'oh!
Sammus
Is it possible to replace each pair of LPG vactrols with a single dual? Looking at the schematic with my amateur eyes looks like you could drop one straight in, perhaps with a small modification to compensate for removing one of the LEDs?

Edit: after a conversation with jml seems this is doable with an adjustment to the current limiting resistor.
Karma
Thanks for advising Dave wink

davebr wrote:
Karma wrote:
hey guys!!! are there any alternative for the toggles switch? C&K are a way too expensive, i wonder if the mountain switch fits, like this http://www.mouser.fr/ProductDetail/Mountain-Switch/108-0044-EVX/?qs=%2 fha2pyFaduhRthU2YSVz8cwTjfhFolTuJcC8NxBJT50%3d for the spdt on off on or other reference

Let me offer my advice where none was asked. I do restorations at the vintageTEK museum and I restore vintage radios and music electronics as a part time business. The most unreliable parts in a 208 are the electromechanical parts - switches, potentiometers/sliders, and sockets. My advice is with the $$ you are going to put into it for parts and your time, you don't want a cheap switch to fail early. I have repaired 208s with crummy sockets and bad switches. The sockets are easy. Replacing a switch is not and you risk damaging the PCB without proper desoldering equipment. If you choose something other than the C&K, make sure they are very reliable.

Dave
we_squirm
Can anyone offer me some advice / help?

I just finished my build. Everything seems to be where it should be. I'm using Romans 211 power supply with a 12V center positive 5A supply.

When I power the 211 power supply up I am getting what I should. -15V, 12V, 5V, all seem good.

When I plug in the 208 to the 211 and turn it on, I get no sound from the 208. The LEDs on the 208 (all of them) just pulse every 4-6 seconds. The little green LED on the power brick I'm using also goes out, but blinks on then off in time with the 208 LEDs. I put my meter on some other tabs on the power supply while this is happening and I barely get any voltage, but when I unplug the 208 and just test the 211 on it's own, it goes back to normal voltage levels. Does this mean something is shorting to ground somewhere? Any other advice? I'm somewhat new to building stuff at this level, but I'm good at soldering. I'm good at following instructions but I've never really had to troubleshoot or trace connections etc... still a bit of a newbie in that area.
cygmu
we_squirm wrote:
When I plug in the 208 to the 211 and turn it on, I get no sound from the 208. The LEDs on the 208 (all of them) just pulse every 4-6 seconds. The little green LED on the power brick I'm using also goes out, but blinks on then off in time with the 208 LEDs.


It sounds like perhaps you have a short circuit somewhere and the power brick is freaking out.

Test for continuity between the power lines on the 208, if you haven't already.

[more detailed answer in response to PM:]
That is, take a multimeter in continuity-check setting (looks like a diode symbol usually, because it is also the diode test setting) and touch the probes to the power connectors on the 208. You are hoping for the meter NOT to beep when you put one probe on the +15V and the other on the 0V connection. Similarly check whether there's continuity from 0V to -15V, and so on for all the power connections. If the meter gives a short beep, that's ok -- this can be caused by a capacitor charging or discharging. If the meter beeps the whole time you have the probes on the connectors, then you have a short circuit between those power lines. The next step is to inspect the boards very carefully and try to figure out where the short circuit is.

If none of the power connections are shorted to one another, that's good, but it also means you need more help figuring out what has gone wrong!
we_squirm
Would it be safe for me to unplug all the cards, and power on the 208 without any cards? And then one by one plug the cards back in? Just figured that would be an easy way to find out where the short might be.
Don T
we_squirm wrote:
Can anyone offer me some advice / help?

I just finished my build. Everything seems to be where it should be. I'm using Romans 211 power supply with a 12V center positive 5A supply.

When I power the 211 power supply up I am getting what I should. -15V, 12V, 5V, all seem good.

When I plug in the 208 to the 211 and turn it on, I get no sound from the 208. The LEDs on the 208 (all of them) just pulse every 4-6 seconds. The little green LED on the power brick I'm using also goes out, but blinks on then off in time with the 208 LEDs. I put my meter on some other tabs on the power supply while this is happening and I barely get any voltage, but when I unplug the 208 and just test the 211 on it's own, it goes back to normal voltage levels. Does this mean something is shorting to ground somewhere? Any other advice? I'm somewhat new to building stuff at this level, but I'm good at soldering. I'm good at following instructions but I've never really had to troubleshoot or trace connections etc... still a bit of a newbie in that area.


How much current can that power brick you're using provide?

And yes, you can power it up without any cards. Power it down again before plugging in a card. I.e., do NOT plug in a card with the power on. Plug Card 3 back in first, then go in any order you like.
tarandfeathers
Envelope sustain boards are now up for sale, along with various other 208/Buchla odds and ends, at http://www.dunningtonaudio.co.uk



Note that these are currently being manufactured and will be shipped in early September.

I'm writing an article that goes into some depth about the design of the envelope generator, the nature of the problem and how it is fixed. That should be up in a couple of weeks, for anyone who is interested.
we_squirm
Don T wrote:
we_squirm wrote:
Can anyone offer me some advice / help?

I just finished my build. Everything seems to be where it should be. I'm using Romans 211 power supply with a 12V center positive 5A supply.

When I power the 211 power supply up I am getting what I should. -15V, 12V, 5V, all seem good.

When I plug in the 208 to the 211 and turn it on, I get no sound from the 208. The LEDs on the 208 (all of them) just pulse every 4-6 seconds. The little green LED on the power brick I'm using also goes out, but blinks on then off in time with the 208 LEDs. I put my meter on some other tabs on the power supply while this is happening and I barely get any voltage, but when I unplug the 208 and just test the 211 on it's own, it goes back to normal voltage levels. Does this mean something is shorting to ground somewhere? Any other advice? I'm somewhat new to building stuff at this level, but I'm good at soldering. I'm good at following instructions but I've never really had to troubleshoot or trace connections etc... still a bit of a newbie in that area.


How much current can that power brick you're using provide?

And yes, you can power it up without any cards. Power it down again before plugging in a card. I.e., do NOT plug in a card with the power on. Plug Card 3 back in first, then go in any order you like.


the power brick i'm using is 12V center positive 5000mA
we_squirm
Alright, So I found the first problem. The program card header was shorting to ground. So I unplugged it. After that, I got sound for a while out of the 208 and everything seemed somewhat functional. The reverb seemed weird and it when I turned it up all I got was what sounded like alien noises.

All of a sudden though all the lights on the 208 panel turned on (except for stages 2-5 of the sequencer) and I lost sound. Now I get nothing. I'm still getting 12V where I need it so I'm not sure what's wrong. Any ideas?
Don T
we_squirm wrote:
Alright, So I found the first problem. The program card header was shorting to ground. So I unplugged it. After that, I got sound for a while out of the 208 and everything seemed somewhat functional. The reverb seemed weird and it when I turned it up all I got was what sounded like alien noises.

All of a sudden though all the lights on the 208 panel turned on (except for stages 2-5 of the sequencer) and I lost sound. Now I get nothing. I'm still getting 12V where I need it so I'm not sure what's wrong. Any ideas?


Double-check all the supply voltages, but especially the +5V line. I learned the hard way that a 208 will "almost" function even if the +5V is not present. It will do many strange things without the 5V present. Also, make sure you have quiet and noisy ground connected at your power supply (hopefully with a ferrite bead), because unless Card 12 is plugged in, one of the grounds will float if not.

If you have an oscilloscope, check the power lines for noise.
Karma
Okay guys i'm ready to order my mouser cart but WTF!!!! 22 week for the 330uH bourns capacitance!!! Do you know any replacement part for this item?
cygmu
Karma wrote:
Okay guys i'm ready to order my mouser cart but WTF!!!! 22 week for the 330uH bourns capacitance!!! Do you know any replacement part for this item?


I'm about to embark on this build so I thought I would try to figure this out for you but I can't work out for the life of me which part you mean. 330uH sounds like an inductor, but you said capacitor, but I can't find anything close on any of the BOMs I'm looking at. Which board is this on?
Karma
Ho i'm sorry this is for the 211 powersupply, i have one cart for the 211, 218, and the 208 and yes it's inductor not capicitor Dead Banana


If someone have an idea

http://www.mouser.fr/ProductDetail/Bourns/5900-331-RC/?qs=%2fha2pyFadu hE%2fdaqyaecUJq%252b48VaccG52DklVBEwZpr9NVPJscx5QQ%3d%3d
cygmu
That part is in stock at tme.eu
Karma
Nice thanks!!
HBCoffin
For those who have built the 211 power supply, does the orientation of the inductors matter? As far as I know they have no polarity, but I've come across some discussions regarding a preferred orientation in some instances. Not sure if it matters for this particular unit.
meatcliff
HBCoffin wrote:
For those who have built the 211 power supply, does the orientation of the inductors matter? As far as I know they have no polarity, but I've come across some discussions regarding a preferred orientation in some instances. Not sure if it matters for this particular unit.


Doesn't matter.
HBCoffin
meatcliff wrote:
HBCoffin wrote:
For those who have built the 211 power supply, does the orientation of the inductors matter? As far as I know they have no polarity, but I've come across some discussions regarding a preferred orientation in some instances. Not sure if it matters for this particular unit.


Doesn't matter.


Wonderful, thanks for clarification. Guinness ftw!
dsf
Quote:
So checking past comments I noticed a mesage from Dimitree telling about a diference in one resistor from the schematics and a real Easel and the 208R BOM, R3 would be 10K...
I`m not an expert but checking the schemos seem that R3 is part of a voltage divider that that goes to the led driver. A quick calculation shown that with R3@1.8K the voltage that goes in the the vactrol led would be lesss than half than the original 10K. So I redid all other mods and just put a 10K in R3.. Night and Day!!! this is a must!! now the timbre folds about 8 times, the simmetry is nice and I can calibrate the LF tracking better!


Can anyone confirm this from the regular 208 Rev2 topic??
EDIT: this made SUCH a different, it is a totally different thing, put the original value or closest back to R9 and preform this.
davebr
dsf wrote:
Quote:
So checking past comments I noticed a mesage from Dimitree telling about a diference in one resistor from the schematics and a real Easel and the 208R BOM, R3 would be 10K...
I`m not an expert but checking the schemos seem that R3 is part of a voltage divider that that goes to the led driver. A quick calculation shown that with R3@1.8K the voltage that goes in the the vactrol led would be lesss than half than the original 10K. So I redid all other mods and just put a 10K in R3.. Night and Day!!! this is a must!! now the timbre folds about 8 times, the simmetry is nice and I can calibrate the LF tracking better!


Can anyone confirm this from the regular 208 Rev2 topic??
EDIT: this made SUCH a different, it is a totally different thing, put the original value or closest back to R9 and preform this.


R3 is on card 7. I verified it does make a big different. On my unit, perhaps too big of a difference. I ended up selecting 8K2 for R3.

Dave
davebr
tarandfeathers wrote:
Envelope sustain boards are now up for sale, along with various other 208/Buchla odds and ends, at http://www.dunningtonaudio.co.uk

Note that these are currently being manufactured and will be shipped in early September.

I'm writing an article that goes into some depth about the design of the envelope generator, the nature of the problem and how it is fixed. That should be up in a couple of weeks, for anyone who is interested.


I bought one and installed it. It works great. I chose to solder it directly to the PCB rather than use sockets and had to fold the disc capacitor under it flat against the PCB.

Dave

Peake
There's a mod to raise the Modulation Oscillator's base pitch with a voltage offset via a switch, but it seems to me an offset will only drive it out of its limited tracking range all the more quickly. Which resistor functions to bring its range down so low? Otherwise the MO is a bit similar to a 258. I'd like to switch between its LF range resistor value and one providing unity with the CO's lowest frequency so their 2-3 octave tracking range will be the same from the same CV (raising the MO's pitch drives it past initial tracking range). Or am I overthinking this, have the offset/switch mod installed in a build but am realizing it may not help. Changing the cap range won't help as it's already the 4700pF value used in the 258 (one mod for the VCS3 LF oscillator is to switch between two caps to shift its range).
tarandfeathers
Peake wrote:
There's a mod to raise the Modulation Oscillator's base pitch with a voltage offset via a switch, but it seems to me an offset will only drive it out of its limited tracking range all the more quickly. Which resistor functions to bring its range down so low? Otherwise the MO is a bit similar to a 258. I'd like to switch between its LF range resistor value and one providing unity with the CO's lowest frequency so their 2-3 octave tracking range will be the same from the same CV (raising the MO's pitch drives it past initial tracking range). Or am I overthinking this, have the offset/switch mod installed in a build but am realizing it may not help. Changing the cap range won't help as it's already the 4700pF value used in the 258 (one mod for the VCS3 LF oscillator is to switch between two caps to shift its range).


I have this mod on mine, set up exactly as you describe with the "Audio Range" position of the switch matching the lowest frequency on the slider (with fine tune controls centred) to the lowest frequency on the CO (~35Hz, I wanted a low C). I get just over 4 octaves of acceptable "unison" in this mode. I calibrated the tracking of the MO with the switch in the up position, because I only care about tracking when it's being used in that range anyway.
tarandfeathers
davebr wrote:
tarandfeathers wrote:
Envelope sustain boards are now up for sale, along with various other 208/Buchla odds and ends, at http://www.dunningtonaudio.co.uk

Note that these are currently being manufactured and will be shipped in early September.

I'm writing an article that goes into some depth about the design of the envelope generator, the nature of the problem and how it is fixed. That should be up in a couple of weeks, for anyone who is interested.


I bought one and installed it. It works great. I chose to solder it directly to the PCB rather than use sockets and had to fold the disc capacitor under it flat against the PCB.

Dave



Great to hear Dave, nice to see these working for folks, I don't think I've ever seen any evidence that anyone fitted the envelope looping board I did, ha! Yeah, I should mention about folding that cap. As you can see in my photos I did my build with all 1% or better MF resistors and all the ceramic caps are TDK C0G which are low voltage, about 50V for the most part so they are very low profile and as luck would have it fit underneath the board quite comfortably, but you can just bend a taller cap over.
Sammus
tarandfeathers wrote:

Great to hear Dave, nice to see these working for folks, I don't think I've ever seen any evidence that anyone fitted the envelope looping board I did, ha!


They have been out of stock since I discovered your store. I'm waiting for them to come back before I order smile
cygmu
Sammus wrote:
tarandfeathers wrote:

Great to hear Dave, nice to see these working for folks, I don't think I've ever seen any evidence that anyone fitted the envelope looping board I did, ha!


They have been out of stock since I discovered your store. I'm waiting for them to come back before I order smile


They seem to be available now:
http://www.dunningtonaudio.co.uk/product/music-easel-infinite-sustain- module/
Sammus
cygmu wrote:
Sammus wrote:
tarandfeathers wrote:

Great to hear Dave, nice to see these working for folks, I don't think I've ever seen any evidence that anyone fitted the envelope looping board I did, ha!


They have been out of stock since I discovered your store. I'm waiting for them to come back before I order smile


They seem to be available now:
http://www.dunningtonaudio.co.uk/product/music-easel-infinite-sustain- module/


I believe the "envelope looping board" referred to is this one: http://www.dunningtonaudio.co.uk/product/music-easel-modifications-boa rd/
cygmu
Sammus wrote:
cygmu wrote:
Sammus wrote:
tarandfeathers wrote:

Great to hear Dave, nice to see these working for folks, I don't think I've ever seen any evidence that anyone fitted the envelope looping board I did, ha!


They have been out of stock since I discovered your store. I'm waiting for them to come back before I order smile


They seem to be available now:
http://www.dunningtonaudio.co.uk/product/music-easel-infinite-sustain- module/


I believe the "envelope looping board" referred to is this one: http://www.dunningtonaudio.co.uk/product/music-easel-modifications-boa rd/


Argh, you're right. Reading comprehension error on my part. Sorry!
tarandfeathers
Sammus wrote:
tarandfeathers wrote:

Great to hear Dave, nice to see these working for folks, I don't think I've ever seen any evidence that anyone fitted the envelope looping board I did, ha!


They have been out of stock since I discovered your store. I'm waiting for them to come back before I order :)


Ah, might be a while. I am intending to do another run at some point, I put my last few from the first batch on the store but I only had 7 or 8 left I think. I need to produce various pick and place/assembly files before I do another batch though (first ones were placed by hand and toaster oven reflowed.) I will do them at some point but not 100% sure when...
Peake
tarandfeathers wrote:
Peake wrote:
There's a mod to raise the Modulation Oscillator's base pitch with a voltage offset via a switch, but it seems to me an offset will only drive it out of its limited tracking range all the more quickly. Which resistor functions to bring its range down so low? Otherwise the MO is a bit similar to a 258. I'd like to switch between its LF range resistor value and one providing unity with the CO's lowest frequency so their 2-3 octave tracking range will be the same from the same CV (raising the MO's pitch drives it past initial tracking range). Or am I overthinking this, have the offset/switch mod installed in a build but am realizing it may not help. Changing the cap range won't help as it's already the 4700pF value used in the 258 (one mod for the VCS3 LF oscillator is to switch between two caps to shift its range).


I have this mod on mine, set up exactly as you describe with the "Audio Range" position of the switch matching the lowest frequency on the slider (with fine tune controls centred) to the lowest frequency on the CO (~35Hz, I wanted a low C). I get just over 4 octaves of acceptable "unison" in this mode. I calibrated the tracking of the MO with the switch in the up position, because I only care about tracking when it's being used in that range anyway.


Very good point. Thanks.
Reese P. Dubin
Feel like I am butting into the party way late with noob questions, so sorry if thats the case!!

Regarding some motherboard components:
Is there a stateside source for the slide pots? OR another part# that works? I have seen some discussion over the years about plastic vs. metal shaft, which suggests at least 2 appropriate parts. I just cant seem to find that info between here, the secret board etc.

Every 200R I have done thus far has used switches from small bear, and the 208 BOM says Digikey. What gives?

I really want to reduce the number of suppliers as much as humanly possible, because god do I hate incidental costs!!

SO incredibly excited to get in the crew with this nasty monster.
Peake
The original Easel used CTS sliders which I believe had plastic shafts, no longer available. The ones Farnell carry are metal shaft; no state-side supplier so consider stocking up in a single purchase enough for a 296, 207, whatever else you plan to build utilizing them. Dave Brown has posted recently that the Digikey switches are C&K, the type used originally, high-quality stuff which in the long run is definitely worth it.
Reese P. Dubin
Thanks Mike.
I think this is likely to be my only Buchla. I can only really get down with my own panel layouts and this is going to be my one excursion.
seeasound
Wondering has anyone thought about modding the 208 to access seperate outputs from the lpgs?

About to embark on this build and this is a feature I would love to implement.

Total novice but have help.
tarandfeathers
seeasound wrote:
Wondering has anyone thought about modding the 208 to access seperate outputs from the lpgs?

About to embark on this build and this is a feature I would love to implement.

Total novice but have help.


The best suggestion I have seen is to replace one of the output jacks with a stereo socket, and wire the output of one LPG to the tip and the other to the ring (the outputs can be accessed from the top of each of the channel level pots).
seeasound
Ok that doesnt seem too hectic cheers!
synthi
The "left" and "right" outputs carry the same signal, but each one have their own buffer/amplifier. I think a good approach would be using the right out as a direct output from LPG2...
Peake
One mod I'd love to see is to tap the osc which doesn't go through the Balanced Modulator out to the interrupting Preamp input jack so the two oscillators are normal'd through it and any external signal interrupts. Basically normal operation with additional functionality. It would require a dummy jack when intending to use the two oscs as two separate signal paths.
astroschnautzer
I have a set of sliders if anybody wants. 60€ shipped in eu.

edit:Sold
gruvsyco
nervous as shit. I just ordered a good chunk of the components for Romans black easel set (208, 218, 211).

    * Mouser cart
    * Rare parts (-ua726, doing the included SMD boards)
    * Vactrols (Xvive 5c1 per Don T's suggestion).
cygmu
gruvsyco wrote:
nervous as shit. I just ordered a good chunk of the components for Romans black easel set (208, 218, 211).

    * Mouser cart
    * Rare parts (-ua726, doing the included SMD boards)
    * Vactrols (Xvive 5c1 per Don T's suggestion).


Why nervous?
gruvsyco
cygmu wrote:
gruvsyco wrote:
nervous as shit. I just ordered a good chunk of the components for Romans black easel set (208, 218, 211).

    * Mouser cart
    * Rare parts (-ua726, doing the included SMD boards)
    * Vactrols (Xvive 5c1 per Don T's suggestion).


Why nervous?


Still fairly new to diy... it sounds like the Easel stuff is going to be a little more difficult... lack of silkscreen and solder mask.
cygmu
Well, what do I know since I haven't built one, but I reckon if you take it slowly and pay attention to this thread, especially Don T's posts, you'll be good.

Exchange "nervous" for "excited" smile
Peake
Be methodical. Print the BOM for each section and cross off each part as you stuff it. It's a large build but thankfully when approached one card at a time it's manageable. Make sure to have on some good music smile
Don T
Peake wrote:
Be methodical. Print the BOM for each section and cross off each part as you stuff it. It's a large build but thankfully when approached one card at a time it's manageable. Make sure to have on some good music smile


I agree! Plus, do NOT be in a hurry! When you get tired (eyes and/or brain), STOP and put it away for awhile, going past this point is when mistakes happen (do NOT ask me how I know). Use good lighting that allows you to see colors accurately, sometimes 1M and 10M resistors look alike in bad lighting, as do 1K and 10K resistors.
davebr
Don T wrote:
I agree! Plus, do NOT be in a hurry! When you get tired (eyes and/or brain), STOP and put it away for awhile, going past this point is when mistakes happen (do NOT ask me how I know). Use good lighting that allows you to see colors accurately, sometimes 1M and 10M resistors look alike in bad lighting, as do 1K and 10K resistors.

Compare the assembled boards against photos. I have fixed several where components were stuffed into nearby but incorrect holes. With no solder mask it is possible to bridge traces. I have fixed those as well. The most critical are on the motherboard as once it is assembled it is a lot of work to pull a motherboard apart. I have fixed several where I have floated wires between boards simply to not have to pull the motherboard.

For some reason, it is difficult to really inspect your own work. I also get boards with unsoldered IC pins, etc. I use water wash flux solder so the boards are CLEAN. When they are clean, you can inspect them. Flux will hide issues. When someone sends me a DIY that never worked, the first thing I do is use a magnifying glass and inspect EVERY solder joint. Especially with this RoHS where you have limited component shelf-life, you can have less than brand new parts or PCBs where the pins don't wet. You can't find those with flux covering them. People pay me good money to simply inspect their boards and finish the soldering or unsolder stuff that shouldn't be soldered.

Personally, I find it easier to inspect a good photo rather than the board. It might be because it is 2D but sometimes I will photograph a large board simply to inspect it.

The other thing to be aware of is if you bought all the parts for all the boards there may be same value capacitors but different types used between boards. Don't get confused and use the wrong type (ceramic vs. film, etc.). Another thing, color codes aren't as colorful and distinct as they once were. Red can look like brown can look like orange. If you can't tell, measure it. Also, people will order the wrong parts. Sometimes when searching, 330R and 330K will come up under the same search and people pick the wrong one. The other thing I do with a DIY is verify part values for every part. With the 208 I simply use my photos as a guide.

Dave
gruvsyco
Thanks guys for all your advice. You all rock SlayerBadger!

I employed most if not all of this (music included) in my most recent effort the TTSH which I’m hoping to fire up this weekend. I really enjoy working on this stuff.
Karl71
Does anybody have the most recent mouser cart to share.thanks in advance.
Reese P. Dubin
In looking at not breaking the bank ordering switches from Digikey (who I dislike), and having successfully used the suggested Small Bear switches in every other 200r build so far, I must ask will they work?

It seems like their version of the ON ON ON dpdt has the function slightly altered which seems to be the death knell for that idea.

Would like to see some confirmation before I go either way. thanks!
tarandfeathers
Reese P. Dubin wrote:
In looking at not breaking the bank ordering switches from Digikey (who I dislike), and having successfully used the suggested Small Bear switches in every other 200r build so far, I must ask will they work?

It seems like their version of the ON ON ON dpdt has the function slightly altered which seems to be the death knell for that idea.

Would like to see some confirmation before I go either way. thanks!


Make sure you get ones with PCB pins, not solder lugs (most other builds use solder lug type switches which will not fit into the board.)

There are other sources for the CK switches which may or may not be cheaper than Digikey. As has been noted elsewhere, once you have the panel and motherboard fixed together you are not going to want to take them apart so it is worth spending an extra few tens of dollars on reliable, name brand switches. If you have to replace just one it's probably going to be a couple of hours job, minimum.
Reese P. Dubin
I just bit the bullet and got the listed switches. Anytime I have used C&K or NKK they actually DO feel that much better.

Heres a whole other can of worms.
Having never too closely studied the architecture of the easel, thinking I would never get to touch one, then just now impulsively diving in, how well will it communicate voltage wise with the outside world? This is very likely going to be the only Buchla in my life, and I am planning to mate it with a TKB rather than 218 (until I do), and all the rest of my DIY stuff.
Is it looking for 15v triggers and 10 or 15 volts to sweep full parameter ranges?
Is modifying it natively for a more serge centric voltage profile a fools errand?

Hopefully in another week I will have all the parts in front of me and can come with more than noob queries.

Also bless everyone who has gone before and blazed a trail for the rest!
Don T
Reese P. Dubin wrote:

Having never too closely studied the architecture of the easel, thinking I would never get to touch one, then just now impulsively diving in, how well will it communicate voltage wise with the outside world? This is very likely going to be the only Buchla in my life, and I am planning to mate it with a TKB rather than 218 (until I do), and all the rest of my DIY stuff.
Is it looking for 15v triggers and 10 or 15 volts to sweep full parameter ranges?
Is modifying it natively for a more serge centric voltage profile a fools errand?


According to the original schematics, the MO and the CO are set up to be calibrated at 1V/Oct.

Yes to 15V triggers, and full range parameter sweep is indeed 10V.
Reese P. Dubin
looks like i will be making a little panel of boosters then
I AM using 3.5mm jacks tho because to hell with tinis!!
Reese P. Dubin
I am in the first leg of measuring 30 some VTL5C3s for matching in the modulator card, and O BOY are these things all over the place! I always knew they were loose but this is loose. some of them are 3x the resistance of the one next in the pile.

I feel like I will be able to get a pretty good set, but my question is this.

Is there a preferable resistance as well as tolerance? would 4 in the upper 3000 ohms range be preferable to 4 that are closer to 1200 ohms?

And now that I will have some idea about a good pile of them, are there any other slots that would best be filled by a low or higher resistance?

Will probably make the pairs in the LPGs close as well.

This has been the most enjoyable build I have done, by far.
Karma
I have a question about this, how did you match them?

I don't know how to do, but i think it's like matching diode, not resistance no?
muncky
Don T gave a brilliant lesson in Vactrol matching on another forum but he’s cool with it, I’ll post into here. Tragically, I got quite into it!!
masterofstuff124
I also am about to finish a 208. got a stack of xvive 5c3 and 5c1. Don T recommends xvive 5c1 so I will be going with that. but Id like to match them. Ill dig through the the old 208 thread and try to find the info this weekend.
muncky
Ok... hopefully DonT doesn’t mind - I’ll bring the pics over shortly...

Quote:
[quote="Don T"]
munckytoo wrote:
Does anyone have any tips/pics for the vactrol matching approach recommended by Dave on the Modular synthesis page? I'm not sure how to go about breadboarding and would be great to match in advance as far as poss:


Sure, I went through this process the other day, and still had the setup on my breadboard.

Step one: Initial set up like this: +15V into power bus strip (yellow wire in photo), 2.2K resistor from power bus to any row you like



Step two: Plug vactrol in with + lead in same row as the 2.2K resistor, attach DMM leads to outer pins of vactrol:



Step three: While watching the DMM display, plug ground wire into the row with the - lead of the vactrol:


Reese P. Dubin
For those of us not using Buchla connectors/supplies, I am assuming N on the power on the motherboard is NOISY GROUND? Also assuming I can again just connect this to the standard ground and deal with any noise that comes with it?

Is there any reason not to do the old fashioned first power up with all the ICs absent? Cant see why not, but I also need glasses.
Karma
Thanks Muncky wink
Don T
Reese P. Dubin wrote:
For those of us not using Buchla connectors/supplies, I am assuming N on the power on the motherboard is NOISY GROUND? Also assuming I can again just connect this to the standard ground and deal with any noise that comes with it?


It's kind of a moot point really, quiet and noisy ground are shorted together on Card 12 anyway. So, to answer your question directly, "yes".


Reese P. Dubin wrote:

Is there any reason not to do the old fashioned first power up with all the ICs absent? Cant see why not, but I also need glasses.


If you don't install IC7 on Card 3, you won't have the +13.5V line, other than that, there should be no problem. If you want to test without the +13.5V line, I see no harm in leaving IC7 out for the initial "smoke test". I'm assuming you soldered the LM380 chips on Card 12 with no sockets, so those will still be in there (unless you haven't installed them at all yet).
Reese P. Dubin
Thanks Don.

I mostly forgot I am still awaiting the Dunnington Envelope board very frustrating

If I get antsy I might just follow the bring up routine at the very beginning of the V2.0 thread, with no expectations of envelope function.
davebr
I just finished calibration and verification of a 208 V2.1 and a 218. I needed to make all the modifications on the motherboard so I added the parallel resistor to lower the pulse input threshold to 5V. The Sequencer and EG triggered fine, but the Pulser would not trigger from the 218 pulse output. I tried triggering it from a function generator and could find no voltage level where the Pulser would trigger in the keyboard setting from the pulse input.

I thought I read a thread recently about this with some explanation but couldn't find it. I would appreciate a pointer to it.

So, in tracing out the pulse input signal it goes through Card 2 to be selected by the Program/Both/Panel switch and then goes to the motherboard where it goes a lot of places but doesn't go to the Pulser trigger switch as shown on the schematics. The run is missing from both V2.0 and 2.1 boards. I added it and had another person add it and we both verified the Pulser will now trigger from the pulse input. Details are on my 208 V2 page and I will also post the V2.0 motherboard image here as well. You can add the wire easily on the rear.

I certainly have never seen this mod posted anywhere before. Is this new?

Dave


Karma
There's a mod for a proper pulse, have you seen this?

https://electricmusicstore.com/blogs/build/touch-activated-voltage-sou rce-model-218

This mod is corrected with the black easel kit where r84 is 20k and r85 is 10k and no more trace to cut
davebr
Karma wrote:
There's a mod for a proper pulse, have you seen this?

Yes, that is not the posting I was thinking of.

Dave
davebr
This isn't specific to the V2.1 boards but I wanted an octave switch for the MO. I dislike drilling an extra hole in the panel and I didn't want to repurpose any jacks, so I built a custom program board that allows me to switch the MO up +1 or +2 octaves. Details are on my 208 V2 page.

Dave

Reese P. Dubin
More amazing work Dave.
Reese P. Dubin
Still need to finish a few little details but am pleasantly surprised to have an otherwise fully functioning (to the best of my knowledge) 208.

Damn it is fantastic. It was 2am so I couldnt turn up as loud as I would have liked but o boy does it sound sweet.
gruvsyco
Just curious how well Romans UA726 boards work. They look simple compared to the other 2 variants. Advantages/disadvantages anyone?
cygmu
gruvsyco wrote:
Just curious how well Romans UA726 boards work. They look simple compared to the other 2 variants. Advantages/disadvantages anyone?


Roman has uA726 replacement boards? I am not sure I knew about that. Can you point me at the information please?
gruvsyco
They come in the new 2.1 board sets. It’s a single SMD component. Ssm2212 I think.
cygmu
gruvsyco wrote:
They come in the new 2.1 board sets. It’s a single SMD component. Ssm2212 I think.


Ah, ok, I wasn't aware.

That is just a matched transistor pair, so will not have the temperature stability properties of the ua726 or the other substitution boards, both of which apply an "oven" technique.

If there is no other temperature compensation then I suppose the oscillators will drift and lose tracking with temperature.
Reese P. Dubin
I used non 'chosen/matched' 3904s and smd tempco, as seen on Dave Browns page. So far so good, planning to go back and use the little PCBs eventually, but for now stability seems fine. Havent scaled it yet. I imagine the specs on modern super pairs are way way tighter than the 726 could ever be.
cygmu
Reese P. Dubin wrote:
I used non 'chosen/matched' 3904s and smd tempco, as seen on Dave Browns page. So far so good, planning to go back and use the little PCBs eventually, but for now stability seems fine. Havent scaled it yet. I imagine the specs on modern super pairs are way way tighter than the 726 could ever be.


Right, but the 726 doesn't need to deal with temperature changes because it is held at a constant temperature.

Anyway, with the addition of the PTC resistor a well-matched pair should do just fine I guess.
bemerritt
Just curious what the rough cost of the components comes out to?
Reese P. Dubin
I think all the 726s should be saved for repairing old military missile guidance systems!

Parts would be in the neighborhood of:
Mouser $350
Digikey (switches) $150
Sliders $75 for USA
Small Bear $15
Vactrols $xxx wildly variable
'Rare' parts $75-150 depending on luck/resolve in searching
UA726s $150-200 but use modern stuff and spend btwn $3-20

then you need a panel/reverb tank/knobs and finishing stuff. it aint cheap but less than a BEMI.

As one of the last people to get to the party, I gotta say this is actually a very straitforward build (2.1). Take your time, keep the build pages, this thread and Dave Brown's page open and all the info is there. Braver people have ironed out seemingly every glitch in this thing, hats off to them all.
bemerritt
Reese P. Dubin wrote:
I think all the 726s should be saved for repairing old military missile guidance systems!

Parts would be in the neighborhood of:
Mouser $350
Digikey (switches) $150
Sliders $75 for USA
Small Bear $15
Vactrols $xxx wildly variable
'Rare' parts $75-150 depending on luck/resolve in searching
UA726s $150-200 but use modern stuff and spend btwn $3-20

then you need a panel/reverb tank/knobs and finishing stuff. it aint cheap but less than a BEMI.

As one of the last people to get to the party, I gotta say this is actually a very straitforward build (2.1). Take your time, keep the build pages, this thread and Dave Brown's page open and all the info is there. Braver people have ironed out seemingly every glitch in this thing, hats off to them all.


Thanks for the rundown. Got plenty of time to search while i build hte MME, just really into the idea of building some complete instruments rather than modules at the moment.
bemerritt
Is there anyone that has a black panel/keyboard that can comment on how it does with fingerprints? Seems like a good deal for a whole set of pcb’s and panels, trying to decide what the negatives are.

Thanks!
Sammus
bemerritt wrote:
Is there anyone that has a black panel/keyboard that can comment on how it does with fingerprints? Seems like a good deal for a whole set of pcb’s and panels, trying to decide what the negatives are.

Thanks!


I do, not finished yet so use is minimal, can't comment on fingerprints. 208 panel is Pcb not alu, which may influence your decision.
bemerritt
Just the info i needed. I was worried that was the case. Too good of a deal not to be.
davebr
Sammus wrote:
I do, not finished yet so use is minimal, can't comment on fingerprints. 208 panel is Pcb not alu, which may influence your decision.


I am not finished with mine either. As a PCB, the panel is now where near as rigid as the aluminum panel. It will be interesting to see how structural it all is when assembled. Can anyone who has completed one comment on any flex in the top panel PCB?

Dave
captnapalm
I'd assume most of the fingerprint factor would have to do with how glossy the finish is. It's pretty glossy as it is now, but if you coat it with a matte finish you won't notice fingerprints so much.
bemerritt
Whelp, black kit incoming.

If anyone stateside wants to split some shipping on parts from Europe, let me know.
muncky
Thanks for the tip Dave, on the Pulser missing link - that was causing me some confusion! Put the link in, and can now trigger the pulser feom an external source (did have to add the parallel 240k resistor too before it worked tho). Only residual question is that I can only trigger 2 if three out of the sequencer/envelope/pulser - when I switch the the third in, the sequencer will lock up. Not sure if that’s a feature or a fault at this point.

Also swapped the r3 on card 7 - huge difference, tho a spot of recalibration now required! Much more fun than the previous 1k8, tho I might give the 8k2 a shot, as gets pretty gnarly at the top of the slider... Rockin' Banana!
folpon
bemerritt wrote:
Whelp, black kit incoming.

If anyone stateside wants to split some shipping on parts from Europe, let me know.


Not interested in splitting shipping but I am almost done with my first build and have a lot of extra rare parts sitting around. Things I ordered too many of. I notice you're in San Clemente -- if you're ever in LA let me know and I will give you my extras. w00t
bemerritt
folpon wrote:
bemerritt wrote:
Whelp, black kit incoming.

If anyone stateside wants to split some shipping on parts from Europe, let me know.


Not interested in splitting shipping but I am almost done with my first build and have a lot of extra rare parts sitting around. Things I ordered too many of. I notice you're in San Clemente -- if you're ever in LA let me know and I will give you my extras. w00t


PM sent!
Peake
Finding it's not necessary to completely undo the front panel connections in order to go back in and work upon the 208 motherboard. It does stress the wiring to the banana jacks and the ones closer to the center have to be coaxed by hand back through the openings but there it is.

Buchla 208 technique r
bemerritt
Just curious what kind of shipping times you all have experienced. Emailed to checkin, but having an expectation would be nice.

The wait is obviously killing me.
bemerritt
Also, looked and couldnt really find an answer. What is the difference in the rev 2 and rev 2.1 BOM's?

THanks
Reese P. Dubin
USPS finally found my Infinite sustain card. What a difference a functioning envelope makes.

Also this is the best deal I could find anywhere on shorting bars
https://www.ebay.com/itm/2X-ITT-Pomona-5165-2-Shorting-Bar-with-RED-Bi nding-post-NICE/192356100304?hash=item2cc95128d0:g:L6MAAOSwlcZZhllR

not the sexiest version but at $2.50 each instead of $14 you cant lose. they say pre owned but are brand new.

now I can calibrate and really get one with it
shipShipley
Hey all,

I'm just getting into this after buying the panels second hand from a fellow wiggler.

I noticed that the front panel is sold out at DIY Hub

I couldn't find a contact there, does anyone know whether more will be made available or if there's another source for the front panels?

Cheers!
bemerritt
I contacted them and they said beginning of the year due to other projects.
shipShipley
Ah, ok...do you know if there's a waiting list or should I just keep checking the site from time to time?
bemerritt
Not sure. Im sure someone else on this board could make you one as well. But if you can wait, its probably the best option to build it up and then get a panel in a couple months.
shipShipley
Good call...I'm sure I won't be done in a couple months anyways, this is my first time making something other than a single function module.
tarandfeathers
Reese P. Dubin wrote:
USPS finally found my Infinite sustain card. What a difference a functioning envelope makes.


Glad it showed up and you got it installed! For me it totally changed the easel from an instrument that does almost what I want to one that does exactly what I want.
shipShipley
Is there any common wisdom on how many extra of each component to order? I guess not so much the rare components, but for example, the ones from Mouser.

Thanks!
bemerritt
just try and check where the price breaks are, mainly for resistors. I personally dont really order too many extras, but rather expect a second mouser order for lost or forgotten parts.
captnapalm
On a build like this I'd order a couple extras of each chip for future troubleshooting ease.
Peake
Yes, CMOS, order a couple extra; resistors tend to be 12 cents each or more but can be .018 cents in quantities of ten, always check for price breaks as they'll sometimes not only save you money but help you stock up.
shipShipley
Cool, good advice thank you all!
bemerritt
Just curious, what do people use for pot values? BOM says 10-100k

Also, 12 days since getting my order confirmation without a peep about shipping, even with a couple emails sent to them. Maybe this week is the week?
shipShipley
I'm putting together my various component orders and I've noticed that there are a few things I can't find through Mouser (I also tried Tayda, but not sure where else to look):

Molex 6 Pin Angled Female (Mouser # 538-09-52-1066)is obsolete. Mouser is suggesting part #538-09-48-1064 as a replacement. The only difference I can see is that the mounting style of the replacement is Straight Pin and the original was Through Hole. Can I use the replacement?

For CARD 3, designator R39/45, the 13M Resistor (Mouser #660-CF1/4LT52R136J) is "Unavailable." They suggest some replacements, but none are 13M...can I use a different value here?

Finally, for CARD 12, the 100pF Ceramic Capacitors (140-50S5-101J-RC) and the 470pF Ceramic Capacitors (140-50S5-471J-RC) are listed as obsolete.

Maybe worth noting that I ordered user boops rare parts kit and don't know exactly what all is included, but I assumed it was the components that just say EBAY under part number.

Any guidance would be very much appreciated! Thanks a lot!
cygmu
For the Molex connector, part 09-48-2061 is the recommended alternative, confirmed by Don T.

For the other parts, almost any alternative will be ok. Any 13M through-hole resistor, and any ceramic caps of the right value and lead spacing.
shipShipley
Great, thank you!

btw, where did Don T. suggest that replacement part? I searched through this thread and others a lot before posting so as to avoid asking repeated questions.

Just trying to be a courteous n00b help
bemerritt
shipShipley wrote:
Great, thank you!

btw, where did Don T. suggest that replacement part? I searched through this thread and others a lot before posting so as to avoid asking repeated questions.

Just trying to be a courteous n00b help


I think around 1/3 of the way down this page is what you are looking for.

https://www.muffwiggler.com/forum/viewtopic.php?t=174863&postdays=0&po storder=asc&start=125

what resistance pots are you ordering? says 10-100k, Im thinking 10k should be fine.
captnapalm
bemerritt wrote:


what resistance pots are you ordering? says 10-100k, Im thinking 10k should be fine.


I've used 50k and 100k and both worked fine. 10k should be good too. Whatever's in stock...
shipShipley
bemerritt wrote:
shipShipley wrote:
Great, thank you!

btw, where did Don T. suggest that replacement part? I searched through this thread and others a lot before posting so as to avoid asking repeated questions.

Just trying to be a courteous n00b help


I think around 1/3 of the way down this page is what you are looking for.

https://www.muffwiggler.com/forum/viewtopic.php?t=174863&postdays=0&po storder=asc&start=125

what resistance pots are you ordering? says 10-100k, Im thinking 10k should be fine.


Thanks for that!

Yeah, I'm using 100K linear pots cuz they were around. Still looking for the LOG ones though. That may be the only thing I'm missing now, which should be easy to find.

What are you doing for vactrols? I can only find the Xvive ones...is that a concern for you at all?
bemerritt
I went with Thonk

https://www.thonk.co.uk/shop/vactrols-vtl5c/

I cleaned them out of their last 13 of the VTL5C1, so i'll have to decide the best place to put the two VTL5C3's.
Peake
Card 5

Here are measured general DC voltage states for a working Card 5 in case anyone needs them.

Modulation switch settings: FM, AM, Balanced External:

IC2 pins
5:  -5.54, +6.89, -5.56
6: +6.78, -5.67, -5.66
12: +6.18, -6.18, +6.17
13: -5.66, -5.66, +6.78

IC3 pins
6: -5.65, -5.65, +6.77
12: +6.89, +6.89, -5.63
13: -5.64, +6.89, -5.63


Readings measured with Index at full and BE selected while trouble-shooting Balanced External mode.

IC 1:

1: +0.528
2: -0.433
3: -6.09
4: -6.09
5: +0.243
6: +0.436
7: -7.42
8: -1.068
9: +0.086
10: +6.73
11: +7.35
12: +6.72
13: slowly varies between +0.080 to +0.094
14: -0.845

IC 4:

1: +0.096
2: +0.094
3: +7.71
4: +0.089
5: +0.097
6: +0.089
7: -14.91
8: +0.097
9: +0.100
10: +0.104
11: +14.67
12:+0.086
13: +0.091
14: +0.103

IC 5:

1: +0.133
2: +0.125
3: +10.27
4: +2.16
5: +0.126
6: +0.103
7: -14.88
8: +0.094 (slowly varies up to 10+mv
9: Same as 8
10: varies from 0.0 to +0.05
11: +14.71
12: +0.089
13: +0.092
14: +0.081
bemerritt
Going to order sliders from Farnell today, so if anyone from the US wants to split shipping, let me know today.
muncky
Going CPC? Cheaper than regular Farnell Guinness ftw!
bemerritt
muncky wrote:
Going CPC? Cheaper than regular Farnell Guinness ftw!


not sure if i follow....
captnapalm
bemerritt wrote:
muncky wrote:
Going CPC? Cheaper than regular Farnell Guinness ftw!


not sure if i follow....


cpc.farnell.com

but the cheapest for US is Newark...
muncky
Yep, Mr Naplam got it screaming goo yo

CPC http://cpc.farnell.com/alps/rs4511150k/lin-pot-50k-45mm/dp/RE00423?CMP =KNC-GUK-CPC-SKU-Resistors_%7C_RE00423&mckv=scdZFEnNC_dm%7Cpcrid%7C191 700952546%7Ckword%7Crs4511150k%7Cmatch%7Cp%7Cplid%7C%7C&gclid=Cj0KCQjw vabPBRD5ARIsAIwFXBkvjRkligLWe5Niplu00Irb3QgCEBxZLdrj82O4UUEKGmjj7NI_Aj IaAn19EALw_wcB

V

http://uk.farnell.com/alps/rs4511150k/potentiometer-slide-50k/dp/11917 30?ost=RS4511150K&iscrfnonsku=false
Karl71
Just got my 2N3565s from UTSource,im a little confused.all the other builds ive seen have used the black button type or silicon.mine are metal can? Is it possible these are some cheap generic fake?
weedywhizz
bemerritt wrote:
I went with Thonk

https://www.thonk.co.uk/shop/vactrols-vtl5c/

I cleaned them out of their last 13 of the VTL5C1, so i'll have to decide the best place to put the two VTL5C3's.


Tons available at samodular.com wink
Reese P. Dubin
Karl71 wrote:
Just got my 2N3565s from UTSource,im a little confused.all the other builds ive seen have used the black button type or silicon.mine are metal can? Is it possible these are some cheap generic fake?


2N's are cans where PN's are blobs. cans work the same, just reverse the direction
Don T
Reese P. Dubin wrote:
Karl71 wrote:
Just got my 2N3565s from UTSource,im a little confused.all the other builds ive seen have used the black button type or silicon.mine are metal can? Is it possible these are some cheap generic fake?


2N's are cans where PN's are blobs. cans work the same, just reverse the direction


Every 2N3565 I have ever seen is a TO-106 (Blob Top). All the PN3565 I have ever seen are TO-92. I have never seen either in a metal can.
Karl71
Don T wrote:
Reese P. Dubin wrote:
Karl71 wrote:
Just got my 2N3565s from UTSource,im a little confused.all the other builds ive seen have used the black button type or silicon.mine are metal can? Is it possible these are some cheap generic fake?


2N's are cans where PN's are blobs. cans work the same, just reverse the direction


Every 2N3565 I have ever seen is a TO-106 (Blob Top). All the PN3565 I have ever seen are TO-92. I have never seen either in a metal can.


Yes, an extensive google has yielded no information or data sheet for the these tin cans.I need to be 100% sure what im putting in there.luckily i have some PNs at hand.thanks for the verification.
davebr
Reese P. Dubin wrote:
Karl71 wrote:
Just got my 2N3565s from UTSource,im a little confused.all the other builds ive seen have used the black button type or silicon.mine are metal can? Is it possible these are some cheap generic fake?


2N's are cans where PN's are blobs. cans work the same, just reverse the direction

Q2 and Q3 on card 6 are the switching transistors for reversing the integrator current at the peaks of the triangle. Any good switching transistor will work fine. Even the venerable 2N3904 will work fine in this application so as long as the transistors you received are NPN and reasonably fast they should work.

Dave
Karl71


I found this useful.
shipShipley
I just want to make sure I'm not missing something. I'm building card 1 and my capacitors are much smaller than the ones I've seen in pictures of the card. I know they can have the same value and be different sizes, but is there any significant difference? Thanks!
cygmu
Nothing to worry about, shipShipley.
folpon
shipShipley wrote:
I just want to make sure I'm not missing something. I'm building card 1 and my capacitors are much smaller than the ones I've seen in pictures of the card.


No, you're all good. I used the same ones. (Also I think I sold you those boards!)

Rockin' Banana!
papz
These caps sound better in multilayer patches hihi
shipShipley
folpon wrote:
shipShipley wrote:
I just want to make sure I'm not missing something. I'm building card 1 and my capacitors are much smaller than the ones I've seen in pictures of the card.


No, you're all good. I used the same ones. (Also I think I sold you those boards!)

Rockin' Banana!

Cool, thanks everyone!

folpon, you did sell me these boards and now my secret identity has been compromised! Only took 4 weeks! seriously, i just don't get it

jk, cool to see you over here!
Karma
Hi guys!! I have an issue, the pulser don’t want to fire in self mode, it can trig when i fire it manually with the toggle switch, i don’t know where start to check Dead Banana
davebr
Karma wrote:
Hi guys!! I have an issue, the pulser don’t want to fire in self mode, it can trig when i fire it manually with the toggle switch, i don’t know where start to check Dead Banana

When in self mode the output is connected to the input with SW10. D1 connects the output back to the input. I have had trouble with intermittent and wobbly 1P3T C&K switches and wrote them about it. It could be intermittent. Or, you could have left out D1 or reversed it. You might be able to inspect the diode from the side or through the slider slots. Otherwise you will have to verify it.

There could be a build issue on the card but I would check those motherboard components first.

I just replaced SW10 and was able to rotate the motherboard up as was posted somewhere on this forum. It worked quite well.

Dave
Karma
davebr wrote:
Karma wrote:
Hi guys!! I have an issue, the pulser don’t want to fire in self mode, it can trig when i fire it manually with the toggle switch, i don’t know where start to check Dead Banana

When in self mode the output is connected to the input with SW10. D1 connects the output back to the input. I have had trouble with intermittent and wobbly 1P3T C&K switches and wrote them about it. It could be intermittent. Or, you could have left out D1 or reversed it. You might be able to inspect the diode from the side or through the slider slots. Otherwise you will have to verify it.

There could be a build issue on the card but I would check those motherboard components first.

I just replaced SW10 and was able to rotate the motherboard up as was posted somewhere on this forum. It worked quite well.

Dave


You’re a genius i forgot D1 it Works well now!!!
davebr
Karma wrote:
davebr wrote:
Karma wrote:
Hi guys!! I have an issue, the pulser don’t want to fire in self mode, it can trig when i fire it manually with the toggle switch, i don’t know where start to check Dead Banana

When in self mode the output is connected to the input with SW10. D1 connects the output back to the input. I have had trouble with intermittent and wobbly 1P3T C&K switches and wrote them about it. It could be intermittent. Or, you could have left out D1 or reversed it. You might be able to inspect the diode from the side or through the slider slots. Otherwise you will have to verify it.

There could be a build issue on the card but I would check those motherboard components first.

I just replaced SW10 and was able to rotate the motherboard up as was posted somewhere on this forum. It worked quite well.

Dave


You’re a genius i forgot D1 it Works well now!!!


Most of those parts are in the circuit for a reason ...
Glad you got it working.

Dave
folpon
Where did you guys get the colored end caps for your sliders? The caps I got from mammoth work great on the switches but all the slider caps are breaking down after a couple days.

Many thanks to all in this thread, btw. I couldn't have built my easel without your help.

folpon
Actually maybe I just pushed them down too far.
Peake
Haven't tried these but they might be better-shaped for the sliders than the ones we've all been using thus far:

https://www.samodular.com/product/switch-caps/

Where it says "Variation" pull down the menu and there's a selection for a full kit of caps for the 208. Thanks wheedywhiz!
papz
Typical switch caps problem : https://www.muffwiggler.com/forum/viewtopic.php?p=2689896#2689896

The ones Peake suggests are softer and fit perfect on sliders and switches.
MechaSeb
If someone is looking for Amphenol EDAC connectors, exactly like the original Buchla 208 (they are significantly better), i still have a few pieces available.

check here
captnapalm
Peake wrote:
Haven't tried these but they might be better-shaped for the sliders than the ones we've all been using thus far:

https://www.samodular.com/product/switch-caps/

Where it says "Variation" pull down the menu and there's a selection for a full kit of caps for the 208. Thanks wheedywhiz!


I bought these and they're the best I've seen, closest to the original 1970s Buchla caps.

Here's a pic of them on my Easel:

Dimitree
does anyone know a mod for the Pulser so that when you put it in "self" mode + "triggered" mode it starts pulsing but its own?
captnapalm
Dimitree wrote:
does anyone know a mod for the Pulser so that when you put it in "self" mode + "triggered" mode it starts pulsing but its own?


Do you just mean so you don't need to 'prime' it by flicking it to 'one' momentarily then back to 'triggered'?
Dimitree
captnapalm wrote:
Dimitree wrote:
does anyone know a mod for the Pulser so that when you put it in "self" mode + "triggered" mode it starts pulsing but its own?


Do you just mean so you don't need to 'prime' it by flicking it to 'one' momentarily then back to 'triggered'?


yes indeed, sorry if the question was not clear in the first place
captnapalm
Dimitree wrote:
captnapalm wrote:
Dimitree wrote:
does anyone know a mod for the Pulser so that when you put it in "self" mode + "triggered" mode it starts pulsing but its own?


Do you just mean so you don't need to 'prime' it by flicking it to 'one' momentarily then back to 'triggered'?


yes indeed, sorry if the question was not clear in the first place


I haven't heard of a mod for this. Perhaps something with the program card achieves it? I know the looping envelope mod doesn't need a kickstart.
Dimitree
captnapalm wrote:

I haven't heard of a mod for this. Perhaps something with the program card achieves it? I know the looping envelope mod doesn't need a kickstart.


ok, thank you,
can you tell me which is the looping envelope mod?
captnapalm
Dimitree wrote:

ok, thank you,
can you tell me which is the looping envelope mod?


A couple people have sold small boards for them. Looks like Dunnington is out of stock but this is essentially it:
http://www.dunningtonaudio.co.uk/product/music-easel-modifications-boa rd/

It's also available on papz's great 208 toolbox, which is the route I went so I didn't modify my panel:
http://www.portabellabz.be/toolbox.html
papz
I still have a few PCBs for envelope looping, they can be mounted to the motherboard and connected to the envelope switch in place of the off position, like on the BEMI, so no modifictaion of the panel.

Feel free to pm me if you want one, but the ToolBox solution is more interesting as the retrig pulse can be delayed up to 8 seconds.

Dimitree
thank you, I'm definitely considering it!

out of curiosity, do you get cool results in modulating via CV the modulator switch ("balanced/AM/FM") or it is useless to control that using CV?
I still don't have a 208 so I cannot understand what results it could give
papz
Modulation switch CV, together with LPG2 routing switch CV, are useful features, I mostly use these when processing external audio via the preamp to create different layers in the patch and make it sound like if there are more audio sources than there actually are.
Dimitree
papz wrote:
Modulation switch CV, together with LPG2 routing switch CV, are useful features, I mostly use these when processing external audio via the preamp to create different layers in the patch and make it sound like if there are more audio sources than there actually are.


cool, perhaps do you have some audio examples?
papz
This is a self-playing patch using a BOB expander only, the external audio is the noise coming from it. Both these switches are voltage controlled, but I don't remember the exact patch. d'oh!
[s]http://soundcloud.com/trapzoid2/bobnoise[/s]

And of course Todd's videos are the best possible demonstration. thumbs up



Karma
What’s your tracking range for CO and MO? I can play CO fine for 3 octave after it detune quickly, and my MO don’t want to tune properly, i changed in card 6 R5 from 190K to 82K, it’s better but not enough, I wonder if it’s safe to decrease another time to 75k for example... i also changed r9 for 330k because the MO range is too low
Peake
3 octaves here as well; even with larger value, multiturn trimpots for HF linearity/tracking they don't help beyond 3 octaves. If there's a way to calibrate with them for greater than 3 I'd love to learn how. I can get good unison at 4 octaves but then the ones below become non-linear.
benadryl
Expecting to be building a black 208r soon. I have been reading this thread looking for answers to a few questions. I'm sure the answers are floating around here but it would be very helpful if someone could answer these.

1. Is it true that the UA726 is not needed for Roman's 2.1 boards? I thought I saw someone say that but I could be wrong.

2. Is it better to use the UA726 or the replacement boards? That is if I need the UA726.

3. What sliders are people using for the build?
captnapalm
benadryl wrote:
Expecting to be building a black 208r soon. I have been reading this thread looking for answers to a few questions. I'm sure the answers are floating around here but it would be very helpful if someone could answer these.

1. Is it true that the UA726 is not needed for Roman's 2.1 boards? I thought I saw someone say that but I could be wrong.

2. Is it better to use the UA726 or the replacement boards? That is if I need the UA726.

3. What sliders are people using for the build?


1. I think Roman is shipping current kits with 726 replacement boards.

2. The 726 is just keeping the osc freq stable at different temps; it's not vital to the sound of the instrument. It's up to you, but if I was building one today I'd save the money and use the replacement boards. They achieve the same thing using a tempco.

3. The Alps sliders from Farnell/Newark are very nice, and what every build I've seen has used. Way better than the old plastic sliders the original Easel used, which caused a lot of problems.
davebr
captnapalm wrote:
benadryl wrote:
Expecting to be building a black 208r soon. I have been reading this thread looking for answers to a few questions. I'm sure the answers are floating around here but it would be very helpful if someone could answer these.

1. Is it true that the UA726 is not needed for Roman's 2.1 boards? I thought I saw someone say that but I could be wrong.

2. Is it better to use the UA726 or the replacement boards? That is if I need the UA726.

3. What sliders are people using for the build?


1. I think Roman is shipping current kits with 726 replacement boards.

2. The 726 is just keeping the osc freq stable at different temps; it's not vital to the sound of the instrument. It's up to you, but if I was building one today I'd save the money and use the replacement boards. They achieve the same thing using a tempco.

3. The Alps sliders from Farnell/Newark are very nice, and what every build I've seen has used. Way better than the old plastic sliders the original Easel used, which caused a lot of problems.

1,2. The expo converter is just a pair of NPN transistors. For best performance you want these closely matched, so a matched pair works best. There is a temperature term in the conversion so the VCO pitch will drift with temperature.

The uA726 solved this thermal drift by adding a heater with feedback to keep the NPN pair at a constant high temperature. Other designs use a tempco resistor to compensate. The replacement board that ships doesn't have a tempco resistor. It is just a SSM2212 matched pair SMT to DIP adapter board. Note there are some uA726 adapter boards that do implement a heater.

You can use this or use any matched pair thru hole transistor. You just have to match the uA726 pinout. I just used taped and reel 3904s which because of the tape and reel are fairly well matched. I had to bend the leads all around and fly two wires You can replace one of the resistors on the card with a tempco to improve performance. However, you really want the tempco thermally connected to the matched pair so I simply epoxied it on top of the transistors and flew wires. The performance is reasonably good. I have information on my 208SPSS page.

Depending on what your needs are you have several options to choose from of which the uA726 is ~$100 and the 2N3904s with a tempco are less than $1.50. The SSM2212 SMT is about $7. Note the tempco resistor I used is on last time buy but there are still ~2400 at Mouser.

3. I agree with the choice of Alps sliders from Farnell/Newark. I think they have way better feel than the plastic.

Dave
Peake
I just did a build with the jhulk uA726 substitute and it worked great. It's heated and you can trim the amount of heat to allow or negate drift amount. Some SMD soldering however. A little more expensive than the SSM option Dave describes directly above. All of these options are viable.
papz
The pA726 is available in 2 versions, one matching the original µA726 round pinout (TO-100), the other specially designed with the 208 in mind (DIP-10).
It works very good, no miniature SMD soldering needed, easy and detailed calibration schedule, easily accessible calibration trimpot.
Hundreds sold, every buyer happy and many returning customers w00t

http://www.portabellabz.be/pa726.html
benadryl
Cool, very helpful. Thank you all!
Karl71
Without going into the embarrassing details,can i replace all of the 4016s on cards 1-4 with 4066s. My understanding is the 4066 is a drop in pin for pin replacement with a lower on resistance,which might make a difference in an audio application but not in logic/switching applications.....yay or nay? Help!
Don T
Karl71 wrote:
Without going into the embarrassing details,can i replace all of the 4016s on cards 1-4 with 4066s. My understanding is the 4066 is a drop in pin for pin replacement with a lower on resistance,which might make a difference in an audio application but not in logic/switching applications.....yay or nay? Help!


Yes!
Karl71
Thanks Don
tarandfeathers
Don T wrote:
Karl71 wrote:
Without going into the embarrassing details,can i replace all of the 4016s on cards 1-4 with 4066s. My understanding is the 4066 is a drop in pin for pin replacement with a lower on resistance,which might make a difference in an audio application but not in logic/switching applications.....yay or nay? Help!


Yes!


They are for the most part interchangeable and should theoretically be more resilient to ESD, which is good since their IO is in some cases connected directly to the banana jacks and program card pins.

I did find however that using a 4066 on card 9 had a detrimental impact on the sine shape in the CO. I tried a number of 4066 types of different ages from different manufacturers, and the same for 4016. All the 4066 type displayed the issue, all the 4016 were clean so I kept a 4016 in this position and used 4066 everywhere else.
Karl71
Thanks tarandfeathers.i was only planning to make the substitutions on the logic cards but this is a nice reminder not to get lazy a little bit further in the build.I will mark my card 9 build sheet with this information.
tarandfeathers
Karl71 wrote:
Thanks tarandfeathers.i was only planning to make the substitutions on the logic cards but this is a nice reminder not to get lazy a little bit further in the build.I will mark my card 9 build sheet with this information.


Just double checked, sorry, I meant Card 8 not card 9, it's IC2 which selects which waveform feeds the waveshape crossfader.
Karl71
What build thread
Don T
tarandfeathers wrote:
Karl71 wrote:
Thanks tarandfeathers.i was only planning to make the substitutions on the logic cards but this is a nice reminder not to get lazy a little bit further in the build.I will mark my card 9 build sheet with this information.


Just double checked, sorry, I meant Card 8 not card 9, it's IC2 which selects which waveform feeds the waveshape crossfader.


Don't worry, I get Card 8 and Card 9 confused all the time!
dsf
BTW i still have NOS UA726 military grade. I'm open to offers-trades...
bemerritt
So I'm about 90% done, so now to the hard parts. Just a couple questions.

1. Is there any docimentation for Romans uA726 replacement cards. I have the SMT IC's but have read tempcos are required. I have some of these 1K (https://modularaddict.com/krl-tempco-resistor) lying around. Will those work? Just epoxy one of those ontop of the IC and connect to the board. (I have a picture somewhere that dave posted)

2. does the below look correct for the program card slot? Do you just bend in the legs on the top one, solder to the extension, and then mount on top of the panel?



3. This one seems dumb, but figured i'd ask anyway. Any reason not to match the vactrols using methods described but with 12 volts? Dont have my power supply up and running yet.


THanks for the help. So close, yet so far away haha
Don T
bemerritt wrote:

1. Is there any docimentation for Romans uA726 replacement cards. I have the SMT IC's but have read tempcos are required. I have some of these 1K (https://modularaddict.com/krl-tempco-resistor) lying around. Will those work? Just epoxy one of those ontop of the IC and connect to the board. (I have a picture somewhere that dave posted)


As far as I know, there is no documentation. If all resistor values for the BOM have been used, which are the same as the original schematics, the tempco should be 330Ω. Panasonic makes an SMT one of the correct value and a temp coefficient of 3300ppm, this is the one you want.

bemerritt wrote:

2. does the below look correct for the program card slot? Do you just bend in the legs on the top one, solder to the extension, and then mount on top of the panel?




This will be the arrangement after assembly, yes. Solder the bottom connector to the motherboard, then solder the extender board to the pins of the top connector just as you have it placed, but make sure the extender board is not plugged into the bottom connector when you are soldering! Yes, you'll need to bend the pins inwards. The top connector and extender is then bolted to the top of the panel, and the extender plugs into the motherboard connector when you mount the panel to the motherboard.
bemerritt
thanks! Just the info I needed on the Tempco.
keninverse
crossposting from the other thread:

Perhaps this is a failure on my understanding...
Transposing sequenced oscillator should be simple as patching something like a 218 preset out to the same oscillator that's being sequenced correct? When I do this I get nothing except when drop the voltage on the preset to a millivolt and it then only transposes down. Am I missing something here? Now if the "keyboard in/out" is "in" and I use the 218 it seems to work but not when patched directly.
Karl71
Hello.I have my MB complete and cards 1-4.everything is working as expected except my sequencer.it gives me 5,4 and 3 steps.but if i toggle to 3 steps it remains locked until I power up again.I know this is an old and solved problem.but I now have 7 decoupling caps on the card and have replaced all ICs three times.is there anything I am missing.could it be mechanical? can anybody tell me precisely which of the ICs is responsible for the step switching.thanks for anybodies patience in advance.
Don T
Karl71 wrote:
Hello.I have my MB complete and cards 1-4.everything is working as expected except my sequencer.it gives me 5,4 and 3 steps.but if i toggle to 3 steps it remains locked until I power up again.I know this is an old and solved problem.but I now have 7 decoupling caps on the card and have replaced all ICs three times.is there anything I am missing.could it be mechanical? can anybody tell me precisely which of the ICs is responsible for the step switching.thanks for anybodies patience in advance.


The LM3900 is the chip responsible for changing the number of steps. Double-check all component values connected to it, also, double-check resistor values and connections on the number of steps switch.
Karl71
Don T wrote:
Karl71 wrote:
Hello.I have my MB complete and cards 1-4.everything is working as expected except my sequencer.it gives me 5,4 and 3 steps.but if i toggle to 3 steps it remains locked until I power up again.I know this is an old and solved problem.but I now have 7 decoupling caps on the card and have replaced all ICs three times.is there anything I am missing.could it be mechanical? can anybody tell me precisely which of the ICs is responsible for the step switching.thanks for anybodies patience in advance.


The LM3900 is the chip responsible for changing the number of steps. Double-check all component values connected to it, also, double-check resistor values and connections on the number of steps switch.


Thanks Don T.Im going to look at the LM3900 and surrounding components.initially with only 2 decoupling caps its locked up on three steps when i toggled for three but also if i was in four or five and clocked the sequencer at audio rate.adding decouplers stopped it locking at audio rates.now Im worried about overkill.Im going to pull the card tomorrow and check values on the motherboard.if the problem persists then maybe pull the switch out too.Im pretty sure all component values are correct as I was working slowlyout of the mouser stock packages.but i hope to be pleasantly surprised.
benadryl
Any place I can find the ICB2E reverb tank in NA? Google returns absolutely nothing.
weedywhizz
You should search for 1BC2E

http://www.tubeampdoctor.com/en/shop_Reverb_Cans_Effects_Accutronics_R everb/Accutronics_Reverb_Can_1BC2E_4677

Cheers
Steffen
captnapalm
benadryl wrote:
Any place I can find the ICB2E reverb tank in NA? Google returns absolutely nothing.


user xpander was selling them in the states as of a year ago. Maybe PM him and see if he still has them?

https://www.muffwiggler.com/forum/viewtopic.php?t=105825&highlight=
Sammus
Email Belton and buy direct.
benadryl
Aha! That would be why. Thank you.
bemerritt
Karl71 wrote:


I found this useful.


Still a little confused on how to wire this up. Obviously pin a to ground on the pre-amp card. Does piun be go to the signal on that card and then ou need to short pin C to pin B?
tarandfeathers
Short A and B. This way when there is no plug inserted the input to the preamp is shunted to ground.
bemerritt
aww, that makes sense. Thanks!
nicdro
Hi all!
Havent gotten far by now (just finished card 6) but wanted to see if the other cards went well. So no i have to admit :(
IC3 of the pulser gets really hot (i cant touch it) and it doesnt pulse unless i switch to both or front panel (card siwtcher) and push the manual switch to one. Then the light turns on and off again. otherwise it is constantly lit. the sequencer doesnt scroll through the steps and the envelope - yeah sometimes the led is lit sometimes it it isnt but not depending where i switch the switches to. Any ideas? It seems everything is caused by the same error but i am really lost and dont know where to start. Please help!
Thanks!
papz
Try and replace ICs, starting with IC3.
I hope for you they are on sockets.

With the control switch to "prog board", the program card settings are used, the panel controls are disabled, so it's normal nothing seems to work if no card is inserted, you should also read the Easel's manual.
nicdro
Thanks Papz. In the meantime i can now say that the sequencer steps through by keyboard input so does the envelope generator. nonetheless the pulser doesnt pulse (only when i manually trigger it). it seems that it is constantly high. ic3 doesnt get hot anymore as i found a little loose metal piece causing a short.
nicdro
The sequencer is not able to trigger the envelope tho. the pulser does neither the envelope, self cycle nor evolve the sequencer.
nicdro
Update: The pulser doesnt self cycle anymore (after i removed the parallel resistor at r56). it does light up when i trigger manually. It does not trigger the env or advance the sequencer. the keyboard trigger in doesnt effect anything.
seriously, i just don't get it
Don T
nicdro wrote:
Update: The pulser doesnt self cycle anymore (after i removed the parallel resistor at r56). it does light up when i trigger manually. It does not trigger the env or advance the sequencer. the keyboard trigger in doesnt effect anything.
seriously, i just don't get it


Did you replace IC3?
nicdro
I replcaed IC3 and it looped for a second or two and then the ic smoked. i tried a third one and same result. where is the issue?


this is the card. possible i have a short on the motherboard?[/img]


nicdro
Voltages at IC3
without any other card installed.

1 0V
2 14,5V
3 0,01V
4 0V
5 14,5V
6 0V
7 0V
8 0V
9 0V
10 0V
11 0V
12 0V
13 0V
14 15V
nicdro
I have continuity on these molex pins

A2 - 9B

A9 - A10

B5 - B11



i have -15 on pin 2 which is not correct by the schematics... motherboard error i guess
nicdro
Fixed it. I opend the panel and it must be a little piece which felt out (or something else) cause i didnt do anything and now it works grin
nicdro
I need help again. Finished Card10 and 12 and checked if my modosc works.
Unfortunately no :(
IC2 of Card6 gets hot. I have no shorts on the molex connectors. these are my voltages at ic2 - pin 10 is suspicious:
1 - 8V
2 - 4.8V
3 - -0.5V
4 - -0.3V
5 - 0.02V
6 - -1.7V
7 - -15V
8 - -2.6V
9 - -0.3V
10 - -1.38V
11 - 15V
12 - 1,5V
13 - -0,5V
14 - 4,1V

Voltages of Molex Connector (Card 6 not installed)
1 - 0V
2 - 13V
3 - 0V
4 - 0.8V
5 - -1.5V
6 - 14.9V
7 - -15V
8 - 15V
9 - 0V
10 - 0V
11 - 0V
12 - 15V

PLEASE HELP we're not worthy
Karl71
Karl71 wrote:
Don T wrote:
Karl71 wrote:
Hello.I have my MB complete and cards 1-4.everything is working as expected except my sequencer.it gives me 5,4 and 3 steps.but if i toggle to 3 steps it remains locked until I power up again.I know this is an old and solved problem.but I now have 7 decoupling caps on the card and have replaced all ICs three times.is there anything I am missing.could it be mechanical? can anybody tell me precisely which of the ICs is responsible for the step switching.thanks for anybodies patience in advance.


The LM3900 is the chip responsible for changing the number of steps. Double-check all component values connected to it, also, double-check resistor values and connections on the number of steps switch.


Thanks Don T.Im going to look at the LM3900 and surrounding components.initially with only 2 decoupling caps its locked up on three steps when i toggled for three but also if i was in four or five and clocked the sequencer at audio rate.adding decouplers stopped it locking at audio rates.now Im worried about overkill.Im going to pull the card tomorrow and check values on the motherboard.if the problem persists then maybe pull the switch out too.Im pretty sure all component values are correct as I was working slowlyout of the mouser stock packages.but i hope to be pleasantly surprised.

Ive checked all component values visually and with multimeter.everything is correct.I just saw on Dave Browns black easel page that he found a faulty 3 throw toggle switch during the build and advices checking all switches before installation.I sure my error is mechanical.a bad switch.
tarandfeathers
nicdro wrote:
I need help again. Finished Card10 and 12 and checked if my modosc works.
Unfortunately no :(
IC2 of Card6 gets hot. I have no shorts on the molex connectors. these are my voltages at ic2 - pin 10 is suspicious:
1 - 8V
2 - 4.8V
3 - -0.5V
4 - -0.3V
5 - 0.02V
6 - -1.7V
7 - -15V
8 - -2.6V
9 - -0.3V
10 - -1.38V
11 - 15V
12 - 1,5V
13 - -0,5V
14 - 4,1V

Voltages of Molex Connector (Card 6 not installed)
1 - 0V
2 - 13V
3 - 0V
4 - 0.8V
5 - -1.5V
6 - 14.9V
7 - -15V
8 - 15V
9 - 0V
10 - 0V
11 - 0V
12 - 15V

PLEASE HELP :hail:


For a start, replace IC2 and retest, though it is possible you have another fault on the card causing it to fail. Pin 10 of IC2 should be an AC signal, you can't measure it with the DC voltage range of a multimeter. Look at it it on an oscilloscope and see what's there.
nicdro
tarandfeathers wrote:
nicdro wrote:
I need help again. Finished Card10 and 12 and checked if my modosc works.
Unfortunately no :(
IC2 of Card6 gets hot. I have no shorts on the molex connectors. these are my voltages at ic2 - pin 10 is suspicious:
1 - 8V
2 - 4.8V
3 - -0.5V
4 - -0.3V
5 - 0.02V
6 - -1.7V
7 - -15V
8 - -2.6V
9 - -0.3V
10 - -1.38V
11 - 15V
12 - 1,5V
13 - -0,5V
14 - 4,1V

Voltages of Molex Connector (Card 6 not installed)
1 - 0V
2 - 13V
3 - 0V
4 - 0.8V
5 - -1.5V
6 - 14.9V
7 - -15V
8 - 15V
9 - 0V
10 - 0V
11 - 0V
12 - 15V

PLEASE HELP we're not worthy


For a start, replace IC2 and retest, though it is possible you have another fault on the card causing it to fail. Pin 10 of IC2 should be an AC signal, you can't measure it with the DC voltage range of a multimeter. Look at it it on an oscilloscope and see what's there.


i got the voltages without ic2 installed. is card11 crucial for the headphone output? i hear a really high pitched sound but very quiet. i will test with ic2 replaced, but that wont keep it cool Dead Banana

update: same with another ic and i have an offest on ic2 pin10 when scoped.
Don T
nicdro wrote:

i got the voltages without ic2 installed. is card11 crucial for the headphone output? i hear a really high pitched sound but very quiet. i will test with ic2 replaced, but that wont keep it cool Dead Banana

update: same with another ic and i have an offest on ic2 pin10 when scoped.


Card 11 is not crucial for headphone output.

But first, based on what you have posted so far, my suggestion is to pull every card, and remove the panel if possible, and check everywhere you can for resistor lead clippings, with a magnifying glass if possible.
nicdro
Don T wrote:
nicdro wrote:

i got the voltages without ic2 installed. is card11 crucial for the headphone output? i hear a really high pitched sound but very quiet. i will test with ic2 replaced, but that wont keep it cool Dead Banana

update: same with another ic and i have an offest on ic2 pin10 when scoped.


Card 11 is not crucial for headphone output.

But first, based on what you have posted so far, my suggestion is to pull every card, and remove the panel if possible, and check everywhere you can for resistor lead clippings, with a magnifying glass if possible.


Hi Don,
I already did and reflowed every solder join on motherboard and the card itself. are the voltages at the molex connector correct?
nicdro
Something new: With the 4066 (IC5) installed, ICs 2,5,6 are getting hot now. Without they stay cool. I replaced IC5 several times - no change.



[/img]
nicdro


bemerritt
So close, yet so far. All i wanna do is plug this guy in...



However my power supply is not supplying the +15 volts. I have reflowed the chip, replaced it, reflowed it again, and still having troubles. Anyone have a schematic, ideas, comments, suggestions? I'll take anything at this point.





weedywhizz
One of your Diodes is placed wrong.
Its the one near C3
bemerritt
you deserve a beer! Guinness ftw!

switched it, but now getting +12 volts, which i would assume to mean either the chip got messed up with the switched diode, a short or a wrong part.

I guess ill try the one extra chip that hasnt been installed and go from there.

Thanks again! Sometimes a second pair of eyes really helps when you are stumped.
Peake
It doesn't hurt to take photos of unstuffed PCBs for quick reference regarding diode and cap polarity etc. I've made it a habit. That black 208/218 is awesome, hope you have it working ASAP!
benadryl
Any tips on the 211 power supply? I didn't realize I'd have to reflow IC2 and IC3 and I've never come across reflow in the simple eurorack SMD I've done before.

Should I suck it up and order a hot air reflow tool or is there a good way to hand solder them?
weedywhizz
Made around 20 of those 211 power boards and just used my soldering iron with 100% success. Just use s small tip.
Will post a blank 211 pcb picture tomorrow.
benadryl
Cool, thanks! I'll try that.
bemerritt
Well a new IC3 didnt help. Resistors match the images posted on modular synthesis.

I guess its time to order replacement capacitors and a IC2 and replace and check
nicdro
nicdro wrote:
Something new: With the 4066 (IC5) installed, ICs 2,5,6 are getting hot now. Without they stay cool. I replaced IC5 several times - no change.



[/img]


I have 15V at Molex Pin 6 (range) and 15 (offset) with no card installed (trimmer has no effect) - these are connected to pin 4 of IC2 which is an out of the ic (http://www.ti.com/lit/ds/symlink/rc4136.pdf). I've cut the traces molex 6 and 12 on the card and then ic1 smoked. really weird. I checked every trace with the schematics on card6 and everything seems to be fine. any ideas people? Thanks!
bemerritt
as soon as i get 15v from my power supply ill poke around for you!
weedywhizz
bemerritt
Thanks! If this next round of de-bugging doesnt work, just gonna buy one from you haha
Synesthesia
nicdro - there is a bit of a tweak to do with the PN3565.

depending on the pin out , the pins needs to be slightly changed. for example, i take mine from Tayda and reverse them ( my tested and approved method )




I can't guarantee this is your issue as i don't know the pinout of the component you used... but please double check this.
nicdro
Synesthesia wrote:
nicdro - there is a bit of a tweak to do with the PN3565.

depending on the pin out , the pins needs to be slightly changed. for example, i take mine from Tayda and reverse them ( my tested and approved method )

I can't guarantee this is your issue as i don't know the pinout of the component you used... but please double check this.


Thanks for the suggestions but i already tried without having them installed.
I bought these (just in case) https://www.ebay.de/itm/201697265826 there is no datasheet available.
i'm also in direct contact with dave brown - he told me card 11 is crucial as long as no reverb is installed. i tried to measure the triangle (ic2 pin3) and square (ic6 pin7) directly and got constant voltages of -13V and +12.
I checked every trace of the ics for there continuity and shorts... i am helpless at this point.
Don T
bemerritt wrote:
So close, yet so far. All i wanna do is plug this guy in...

However my power supply is not supplying the +15 volts. I have reflowed the chip, replaced it, reflowed it again, and still having troubles. Anyone have a schematic, ideas, comments, suggestions? I'll take anything at this point.





L4 is blown, replace.
bemerritt
Not that i dont believe you, more curious in how you can tell so i know for hte future. Figured L2 could be blown since it was connected to the misplaced diode, but never thought of L4.

Thanks for all the insight!
bemerritt
A new L4 showed up before the rest, should I wait to replace the diode as well, or put it in and cross some fingers?
search64
bemerritt wrote:
Not that i dont believe you, more curious in how you can tell so i know for hte future. Figured L2 could be blown since it was connected to the misplaced diode, but never thought of L4.

Thanks for all the insight!


It looks like it's exploded. Compare to L2 which looks neat and straight.
papz
Tips for the year SlayerBadger!

Tip 1 : calibrate the oscillators tracking properly

The 208s I build (with the pA726 expo converter) track on 5 octaves. A fine calibration needs subtle selection on test of R5 and R58 on board 6 and R14 and R44 on board 7.

I calibrate the tracking on a 208 with a 218.

I first adjust the offset and range trimpots with a frequency counter in a way the frequencies come close to what's written on the panel.

Then I adjust the HF (and LF for the CO) tracking trimpots and the panel "(trim)" ones together, and change the aforementioned resistors if the HF trimpot is off range, using a chromatic tuner (mine is Boss TU-2 )
To me, proper calibration means all the notes played with the 218 are in tune with MO initial frequency C0 (32.7Hz) and CO initial frequency C1 (65.4Hz).

In my latest build, calibrated for 1.2V/oct. :

Board 6
R58 : 390k
R5 : 91k

Board 7
R14 : 44k (68k added in parallel with 120k)
R44 : 150k
R45 : 100k trimpot

These values are suggestions and might not be ideal in another 208 or with another expo converter, why selection on test is needed for R58 and R44.
R5 and R14 values are ok for 1.2V/oct., should be ok for 1V/oct. and probably won't be ok for 2V/oct.
It's a time consuming work : 5-10 minutes warm up time and calibration adjustment are needed for each resistor change.

Tip 2 : reduce or eliminate the bleed of the envelope and pulser into the oscillators frequency

The drift is actually caused by the LED.
Add a resistor in series with it helps very much but reduces the LED brightness. The resistor value depends on the LED type used. Select it on test, 10k is good value to start with, then adjust to get a good compromise between LED brightness and oscillator stability.

The resistor can be added to the solder side of boards 3 and 4.
Cut the trace between the 2N1711 and the Molex connector (there's only one) and bridge the cut with the resistor. That's all folks.



Enjoy ! w00t
tarandfeathers
papz wrote:

Tip 2 : reduce or eliminate the bleed of the envelope and pulser into the oscillators frequency

The drift is actually caused by the LED.
Add a resistor in series with it helps very much but reduces the LED brightness. The resistor value depends on the LED type used. Select it on test, 10k is good value to start with, then adjust to get a good compromise between LED brightness and oscillator stability.

The resistor can be added to the solder side of boards 3 and 4.
Cut the trace between the 2N1711 and the Molex connector (there's only one) and bridge the cut with the resistor. That's all folks.



Enjoy ! :party:


I also noticed this. I used some Wurth 635nm LEDs in mine, not the part from the BOM, these are close to the wavelength of a neon lamp which I think looks cool. They are very high brightness so I increased all series resistors to make them a more sensible level. After this all the fluctuations and bleed were gone (or at least at a level where I can't perceive it. FWIW the LEDs in the gates also have an effect, as you open the gates and the LED brightness increases you can hear the oscillator pitch droop. I recommend using high output LEDs and increasing the resistors for all of them, including the sequencer and gates.

I guess there is some bad 0V routing on the motherboard and the additional current when the LEDs are lit increases the voltage drop in the 0V path which detuned the oscillators.
papz
Interesting, the sequencer LEDs influence sounds acceptable to me but the LPG cause some drift indeed, although not as strong as the pulser or EG.
But disconnect the LPG LEDs didn't help, so I didn't even try with the series resistor resistor, I'll give a deeper look though.
The LEDs of the BOM are too bright to me, I'm not a big fan of bright LEDs, the ones I use in my builds are much softer.
tarandfeathers
papz wrote:
Interesting, the sequencer LEDs influence sounds acceptable to me but the LPG cause some drift indeed, although not as strong as the pulser or EG.
But disconnect the LPG LEDs didn't help, so I didn't even try with the series resistor resistor, I'll give a deeper look though.
The LEDs of the BOM are too bright to me, I'm not a big fan of bright LEDs, the ones I use in my builds are much softer.


To be honest the sequencer shouldnt make any difference as there is always one LED lit and always at the same current. The current through the LEDs in the stock BOM is designed for 1972/3 LED technology, yes its way too much for modern parts, I nearly went blind from the stock values! The LEDs I used only need about 1mA or so for good output. Enough for daylight operation and certainly for studio or stage mood lights...
papz
I noticed a very slight drift when the sequencer is running, obviously related to the passage of a LED to another. But it's really acceptable indeed.

With the softer LEDs I use (I *think* are Mouser part # 696-SLX-LX3044HD), I get perfect brightness using the BOM values and the difference with the added 10k series resistors on board 3 and 4 is very slight.
I just finished servicing a 208 built by someone else who sent it to me for debugging and calibration, whose LEDs are very bright (maybe the BOM's ones ?), the series resistors added as described above cause a stronger brightness difference altough the 10k value is the same.
bemerritt
Ended up being a faulty IC2. Got goosebumps when i heard it for the first time. Now to get the 218 up and running today, finish the case and troubleshoot.

Everything seemed to work except the mod oscillator, but that might have been my nooby self having some switches in the wrong place seriously, i just don't get it ? either way, was super excited to finally get it powered up.
bemerritt
Couple case questions for those who have one or made one or even seen one.

Depth - I presume it makes the most sense to put hte power distribution under the 218 since it is much shallower. Do you then make hte case just deep enough to clear the 208 cards? Is it smart to add some kind of support for the cardes, ie esd foam? Or does that just more easily transfer the force from bumping the case around?

Ground - Am i right in thinking it makes sense to add a banana jack next to my power inlet that is connected to ground? In the future I will most likely cross patch with a euro system, so this seems to make sense.

Any other tips/tricks? Ill be making a case similar to a pitts move 208 (euro) case. So i have flexibility to do whatever i please.
Karl71
bemerritt wrote:
Couple case questions for those who have one or made one or even seen one.

Depth - I presume it makes the most sense to put hte power distribution under the 218 since it is much shallower. Do you then make hte case just deep enough to clear the 208 cards? Is it smart to add some kind of support for the cardes, ie esd foam? Or does that just more easily transfer the force from bumping the case around?

Ground - Am i right in thinking it makes sense to add a banana jack next to my power inlet that is connected to ground? In the future I will most likely cross patch with a euro system, so this seems to make sense.

Any other tips/tricks? Ill be making a case similar to a pitts move 208 (euro) case. So i have flexibility to do whatever i please.
thats my thought as well for a common ground.I saw that Samodulars boats have a ground to banana wired directly from the power on switch.or maybe Samodular can chime in.his boats can be viewed on his store page.
bemerritt
So after playing around with it for a while, it seems my main issue is with the mod osc.

- At first I was getting a very high note, with the frequency slider working in reverse.
- I then noticed that my roman boards for the uA726 that i had mounted with pin headers could possibly be shorting on the adjacent board.
- Removed card 6, trimmed headers and noticed the tempco i had epoxied to the IC had a loose connection.
- Replaced tempco with a sandard resistor
- Now my mod osc acts as below, very low frequency, the fequency slider does work properly and i can modulate the complex osc with it. Video shows me cycling the wave forms




Obviously the waveforms dont look to great either.

So now I am going to look at other adaptations for the uA726, as that is my prime suspect. Any other ideas?

side note: it seems the newer BEMI easels have a frequency range switch, which these do not have anywhere, correct?

Thanks!
nicdro
bemerritt wrote:

- Removed card 6, trimmed headers and noticed the tempco i had epoxied to the IC had a loose connection.
- Replaced tempco with a sandard resistor

Sorry for not able to help you but where did you install the tempco? I've used the ua726 board from roman as well and having problems with my mod osc (very low in frequency - sloth slow)
bemerritt
nicdro wrote:
bemerritt wrote:

- Removed card 6, trimmed headers and noticed the tempco i had epoxied to the IC had a loose connection.
- Replaced tempco with a sandard resistor

Sorry for not able to help you but where did you install the tempco? I've used the ua726 board from roman as well and having problems with my mod osc (very low in frequency - sloth slow)


Well, considering I am having a sloth slow mod osc, sounds like we are in this together!

R12 is where i put a tempco and epoxied it to the top of the IC on the adaptor board. Problem is, that the 330R tempco is a 603 surface mount part, and it is the opposite of fun to attach to some trimmed leads and get into position. A couple pages previous I think someone helped me out with this. I'll look for it.
nicdro
bemerritt wrote:
nicdro wrote:
bemerritt wrote:

- Removed card 6, trimmed headers and noticed the tempco i had epoxied to the IC had a loose connection.
- Replaced tempco with a sandard resistor

Sorry for not able to help you but where did you install the tempco? I've used the ua726 board from roman as well and having problems with my mod osc (very low in frequency - sloth slow)


Well, considering I am having a sloth slow mod osc, sounds like we are in this together!

R12 is where i put a tempco and epoxied it to the top of the IC on the adaptor board. Problem is, that the 330R tempco is a 603 surface mount part, and it is the opposite of fun to attach to some trimmed leads and get into position. A couple pages previous I think someone helped me out with this. I'll look for it.

Is this essential to do? I mean sloth slow like i can count every 0.001V step with a DMM at ic2 pin3 - dont know if oscillation is even the right name for that slowness haha - still working on it with dave brown.
IF i have anything working i will report here. Dave told me to check and verify the TR8 and TR6 as well as the R83 resistor on the motherboard - they are good at mine.
Peake
Edit: You're already working on it with Dave
nicdro
Peake wrote:
One of the oscillators, I forget which and didn't find an answer going several pages back in this thread, has its general frequency set via one of the resistors in the build which can be changed to bring it up or down. Hoping that's the issue and someone who knows the answer will chime in.

on card6 you can bridge pin4 and pin5 of ic4 with a 2k to 10k resistor to set a fixed frequency. this is what i was told.
bemerritt
Well i looked back and it looked like some people had to flip the legs of the transistors. Tried that and didn't work, so i put them back to how i "thought" they were before. Then this happened.



SlayerBadger!

I have to have the frequency range all the way up, so it looks like I will test some resistors between pins 4/5 of ic4
captnapalm
bemerritt wrote:


side note: it seems the newer BEMI easels have a frequency range switch, which these do not have anywhere, correct?

Thanks!


Correct, the originals didn't have this; it was a feature added by BEMI.

On mine if I want a higher frequency, I patch a voltage from one of the "preset voltage source" pots on the 218 into the freq input of the MO.
folpon
bemerritt i'm so proud of you right now. congratulations. smile

for the record I also have a somewhat slow mod osc that doesn't track well. (I have the parts on hand to try some fixes but haven't had the time.) Does yours get to audio rate if the slider and fine tune pot are all the way up?
bemerritt
folpon wrote:
bemerritt i'm so proud of you right now. congratulations. smile

for the record I also have a somewhat slow mod osc that doesn't track well. (I have the parts on hand to try some fixes but haven't had the time.) Does yours get to audio rate if the slider and fine tune pot are all the way up?


Thanks for the positivity! Yeah, haven’t measured it, but definitely gets into audio range. Pretty low, though.
nicdro
bemerritt wrote:
folpon wrote:
bemerritt i'm so proud of you right now. congratulations. smile

for the record I also have a somewhat slow mod osc that doesn't track well. (I have the parts on hand to try some fixes but haven't had the time.) Does yours get to audio rate if the slider and fine tune pot are all the way up?


Thanks for the positivity! Yeah, haven’t measured it, but definitely gets into audio range. Pretty low, though.

You might try to change R9 of card6 to 330k or even higher to get a higher frequency.
bemerritt
THanks ill try that as well. For some reason last night it went back to the high frequency pitch again, with reverse slider action. Then later went back to being correct. Must be something loose...
nicdro
Ok I replaced IC4 with two 2N3904 and now it oscillates! Dave Brown did an awesome job narrowing it down and helping as well as explaining things.
Still have to do the complex osc cards and calibration. Bemerritt , hope you figure it out soon! Did the R9 resistor do anything?
bemerritt
Right now it is working, so haen't changed anything yet. Working on the case and the 218, which is working except for trigger out. So i need to verify i implememnted the mods correctly.

Glad to hear yours is working, time to get busy with the rest of it!
edwinm
nicdro, are you saying you replaced the uA726 on card 6 with two 2N3904's? Do you have any further details? I can't get my modulation oscillator to oscillate so perhaps this is the solution!
Karl71
edwinm wrote:
nicdro, are you saying you replaced the uA726 on card 6 with two 2N3904's? Do you have any further details? I can't get my modulation oscillator to oscillate so perhaps this is the solution!
the 2N3904s are a temporary solution, in the absence of a Ua726 or Potabellabz adapter.it helps to clarify that the circuit works.
bemerritt
218 working, still cant believe this is just sitting there, waiting to be played whenever i feel like it.

Side note: Dont use small bear switch caps, the blue and red ones cracked almost immediately. Will probably get some from sam modular at some point, unless someone stateside has some that dont crack.

nicdro
Get the switch and slider caps from mouser. Great haptic and softer so they don’t crack.

https://www.mouser.de/productdetail/mountain-switch/108-00341-ev?qs=pa uJpjJdVLhkeXbe1RjmyQ%3D%3D

Yes i used two 2n3904. Dave brown has some tips on his page - I will see if it works good enough for me or if I need another solution. But no more Roman‘s smd solution for me. I’ve checked everything with Dave and replacing ic4 helped in the end - perhaps this would solve your problem as well!

http://modularsynthesis.com/modules/tips/tips.htm
bemerritt
thanks for the link, ill give them a try. Luckily i have orange ones already from boops. Smallbear have really nice soft touch ones, but not in all the colors needed.
Peake
The uA726 is a pair of matched NPN transistors with a heater to hold them at a stable temperature. From Dave's page:

http://modularsynthesis.com/roman/buchla258/discrete_pair_uA726.jpg

People are saying these switch and slider caps are the best; pull down the "Variation" option for the 208 kit.

https://www.samodular.com/product/switch-caps/
edwinm
Thanks Peake and Karl71, I'll give the 2n3904s a try
Karl71
Ok.Im having trouble with audio out and Im not sure where to start.Ive been trouble shooting my MO with Dave and it turns out its fine.its working.I can only hear it when I have the monitor out maximum volume and my speakers cranked.I began to suspect Card 11 but I can hear the lpgs opening and closing with no signal but only at extremely high volume.Im now suspicious of Card 12.I installed my reverb tank and raised the reverb volume.I tapped on the tank and nothing! from my experience with guitar amp spring reverb I should be hearing the sproing of the spring vibration.can any one verify this.with no signal output that the spring reverb can be sproinged.I apologise for the loose terminology.
papz
Card 11 output is via R36 (220 ohms) or Molex pin 3. With the routing switch in central position can you monitor MO signal there with a scope ?
Can you hear LPG1 CO output in LPG2 with the routing switch in lowest position ?
If yes, card 11 is not in cause.
If not, try and track the signal following schematics, MO input is Molex pin 9 (it's quite low), or swap all ICs on card 11 anyway and double check all solder joints for a bad one or a bridge.
If you have no MO signal at Molex pin 9, check the headers solder joints and it's not shorted to ground.

If there's no signal at all from LPG2 regardless of the switch position, it's good to also double check the sliders, pot and R71 33k resistor connections on the motherboard.

If the problem was on card 12 you shouldn't hear the CO/LPG1 either because both LPG outputs are summed.
I'm not sure the reverb problem is related.
bemerritt
Seems like a lot of MO problems/not problems lately. Did we all use romans replacement boards? or just a coincidence?
papz
I don't know but you all should use the pA726 hihi
http://www.portabellabz.be/pa726.html

PCBs pairs for 208 will be available again very soon, I just received the new ones and need to test all is fine before offering them.
Price is €30 shipped for 2 PCBs.

bemerritt
Yup, waiting for those to go back in stock! will hopefully be ordering those next month.

Might be a longshot, but a black toolbox would be most appreciated!
papz
A black ToolBox is definitely possible, but the price would depend on how many people are interested. cool
Doing few PCBs is expensive.

Please let know if you're interested in https://www.muffwiggler.com/forum/viewtopic.php?t=195008
Thank you
Karl71
bemerritt wrote:
Seems like a lot of MO problems/not problems lately. Did we all use romans replacement boards? or just a coincidence?
I used Ua726a.I thought it was smoked and tried the 2n3904s.when I heard signal at very high volume , I put the Ua726a back in and I could hear it trmendously low.I can also hear the different waveshapes.Ive applied pitch with the sequencer and it tracks.Ive also used the mod cv banana out to modulate the pulser period and it works.Im just not getting output.the problem is elsewhere.
Karl71
papz wrote:
Card 11 output is via R36 (220 ohms) or Molex pin 3. With the routing switch in central position can you monitor MO signal there with a scope ?
Can you hear LPG1 CO output in LPG2 with the routing switch in lowest position ?
If yes, card 11 is not in cause.
If not, try and track the signal following schematics, MO input is Molex pin 9 (it's quite low), or swap all ICs on card 11 anyway and double check all solder joints for a bad one or a bridge.
If you have no MO signal at Molex pin 9, check the headers solder joints and it's not shorted to ground.

If there's no signal at all from LPG2 regardless of the switch position, it's good to also double check the sliders, pot and R71 33k resistor connections on the motherboard.thanks papz.Ive been over the schematics and will do some probing tonight.If I had enough components I would start building up the 208p MO, LPGs and Card 12 to cross check.but its going to be midweek when my mouser order arrives and who knows when the UTsource stuff arrives
Karl71
My previous message got mixed in with the quote,
papz
The new pA726 works and is available. applause

http://www.portabellabz.be/pa726.html#208

papz
Looks like there's a problem with the replies in this thread, they display in Karl71's latest post... hmmm.....
Don T
Ladies and Gentlemen,

For multiple reasons, I will not be finishing the build started on this thread. Whoever wishes can finish up the build information on the remaining portions if they so desire.

Best of luck to all!
nicdro
papz wrote:
A black ToolBox is definitely possible, but the price would depend on how many people are interested. cool
Doing few PCBs is expensive.

Write me down for this one as well! applause

Mine is now fully (most of it) set. Just needs to be calibrated but it sound… WOW!
The AM is not doing as i would except it would and the inverter out gives me a constant voltage but this will be fixed real'quick i hope.

The 218 is next - hope it is a faster build tho lol
Karl71
Don T wrote:
Ladies and Gentlemen,

For multiple reasons, I will not be finishing the build started on this thread. Whoever wishes can finish up the build information on the remaining portions if they so desire.

Best of luck to all!
thats a shame.would really loved to have seen it through.thanks for consolidating all this information from the various threads.it was a game changer and made the build a possibility.respect to everybody who asked a question and eveybody who replied.
Sammus
papz wrote:
A black ToolBox is definitely possible, but the price would depend on how many people are interested. cool
Doing few PCBs is expensive.


I'm also interested a black toolbox. Possible up to 4 of them.
Sammus
Don T wrote:
Ladies and Gentlemen,

For multiple reasons, I will not be finishing the build started on this thread. Whoever wishes can finish up the build information on the remaining portions if they so desire.

Best of luck to all!


Thanks Don, this is an incredibly useful resource.
papz
Please post or repost your interest for a black ToolBox in the dedicated interest check thread, it will be easier to count. Thank you.

https://www.muffwiggler.com/forum/viewtopic.php?t=195008
edwinm
I'm still trying to debug my board 6 and would reeeaaally appreciate some help!. I've tried two 2N3904s instead of the ua726, swapped all the ICs for new ones and replaced the 2N3565s but I still don't get any oscillation. Can someone tell me what is the first point on the schematic where I should see an oscillating signal? Thanks!
nicdro
edwinm wrote:
I'm still trying to debug my board 6 and would reeeaaally appreciate some help!. I've tried two 2N3904s instead of the ua726, swapped all the ICs for new ones and replaced the 2N3565s but I still don't get any oscillation. Can someone tell me what is the first point on the schematic where I should see an oscillating signal? Thanks!

Check for oscillation: pin3 of ic2; pin3 of ic6
Check if you get a voltagechange at Edge pin6 and 12 (Molex Pins) while moving the freq slider. And check the emitters of q2 and q3 - what does it read? It should switch on and off afaik.
edwinm
Hey, thanks! So no voltage change on 6 and 12 when moving the freq slide but there is change on 5. Pin 3 on ic2 and ic 6 both go high and so do the emitters on q2 and q3. I've double checked that q2 and q3 are orientated correctly.

So I guess I should start by looking for issues between molex pin 5 and pins 6 and 12?
nicdro
Right. What I understood is that the frequency voltage goes from the mb via pin5 to the card to ic2 thru r9 and a couple of things. From the card via pin6 back to the motherboard, thru trimmers (not sure about that tho) and then back to the card via pin12 and into the ua726 thru r12.
Karl71
I had a similiar problem and Dave Brown was incredibly helpful in locating the signal.this is from Dave

That signal goes through the analog switch IC3 and is amplified by IC2 pins 12, 13, 14. Pin 13 is the input. Verify you have a 0 to 6V signal there. Then verify you have gain on pin 12. The gain should be 1+25/62. My calculations say +3.6V/-3.8V which is 7.4V pk-pk which agrees with the notes for pin 4.



See if any of those measure the same.



I would check resistors for correct values. R31, R32, R29, R28, R52m R27, R26, R22. Brown and red, and red and orange can look the same so you might need to measure.
Karl71
Also if you have a scope pin 3 of IC 2 should give you a nice triangle wave.take the far right banana out foe mod cv and input it to the pulser period cv in whilst it clocks your sequencer.is it modulating the pulser and sequencer speed? hope this helps.my problem was at LPG 2, no audio.I had a 330r in place of a 330k.
edwinm
Thanks Karl, I'll go through those pins tomorrow. I've checked resistor values but will check again!

What's confusing me at the moment is that adjusting trimmers TR6 and TR9 has no effect on the voltage of pin 12 of Molex 6 on the motherboard (with card 6 removed). It stays at around 15v. This can't be right can it?
nicdro
Maybe there is a short to +15V
Dave told me that the reason that you don’t see any change while adjusting the trimmers has something to do with the circuitry and the impedance of you DMM. Should be ok!
davebr
nicdro wrote:
Maybe there is a short to +15V
Dave told me that the reason that you don’t see any change while adjusting the trimmers has something to do with the circuitry and the impedance of you DMM. Should be ok!

Actually, edge pin 12 is the base to the expo pair and only changes 18 mV per octave. So with a 5 or so octave range change with the slider, the voltage changes just 90 mV.

Dave
cygmu
Over on emcloned Roman has asked for a list of corrections to the boards, which he will then correct for his final PCB designs on this project.

So if you are aware of a correction that should be made, please let Roman know!
search64
Ask him if he can add the arpeggiator to the 218. Would make it perfect.
Karl71
Its been 4 1/2 months and finally my 208r is alive.this evening whe I sat down to familiarise myself with the calibration process, my scope shots showed my CO waveforms were being modulated slightly,with nothing patched and all sliders at 0.it looks like they are belly dancing.has anybody had the same problem? Could anybody suggest where I might start to look.thanks.
papz
Adjust the CO waveshape trimpot should help.
Karl71
papz wrote:
Adjust the CO waveshape trimpot should help.

Thanks papz.I did try as per Dave Browns page.but I couldnt get a stable waveform.after I posted I looked at card 9 and I remembered I had no 40k2 or 49k9 resistors.I think they were back ordered on mouser at the time.so I paralelled and seriesed as tight as I could.Im wondering was it tight enough.
davebr
Karl71 wrote:
papz wrote:
Adjust the CO waveshape trimpot should help.

Thanks papz.I did try as per Dave Browns page.but I couldnt get a stable waveform.after I posted I looked at card 9 and I remembered I had no 40k2 or 49k9 resistors.I think they were back ordered on mouser at the time.so I paralelled and seriesed as tight as I could.Im wondering was it tight enough.

Is the modulation related to the MO frequency or something else? You can email me and we can continue this offline if you like. We need to figure the source. It is either the MO, the two COs beating against each other, or a random oscillation. Once we figure that, then we know where to start looking.

Dave
Karl71
davebr wrote:
Karl71 wrote:
papz wrote:
Adjust the CO waveshape trimpot should help.

Thanks papz.I did try as per Dave Browns page.but I couldnt get a stable waveform.after I posted I looked at card 9 and I remembered I had no 40k2 or 49k9 resistors.I think they were back ordered on mouser at the time.so I paralelled and seriesed as tight as I could.Im wondering was it tight enough.

Is the modulation related to the MO frequency or something else? You can email me and we can continue this offline if you like. We need to figure the source. It is either the MO, the two COs beating against each other, or a random oscillation. Once we figure that, then we know where to start looking.

Dave

Dave my MO is looking really good so I dont believe thats the problem.I think its the two CO beating as the visible modulation increases with an increase in frquency of the CO pitch slider.If I remember my triamgle output on card 9 was quite good too.I have replacement resistors coming tomorrow so I will swap them out.
papz
From memory, the timbre trimpot setting also caused spurious oscillation in some builds. Try and adjust the timbre, waveform and card 9 trimpots together could help.

If the parallel resistors have the good value within 1% tolerance, they are not in cause.
Karl71
papz wrote:
From memory, the timbre trimpot setting also caused spurious oscillation in some builds. Try and adjust the timbre, waveform and card 9 trimpots together could help.

If the parallel resistors have the good value within 1% tolerance, they are not in cause.

Yeah papz I spent a good deal of time matching the resistors.I went through every resistor I had to find the tightest values.Ithink the problem is with the trimmers.last week when I scoped card 8 CO out from the edge connectors It was good.I think the problem began when I started moving trimmers.Im going to sit down with it later this evening and center everything and work from there.I also have most of the components for your 208p arriving tomorrow,so I might just build up cards 7-9 and see how it behaves.
davebr
Karl71 wrote:
Yeah papz I spent a good deal of time matching the resistors.I went through every resistor I had to find the tightest values.Ithink the problem is with the trimmers.last week when I scoped card 8 CO out from the edge connectors It was good.I think the problem began when I started moving trimmers.Im going to sit down with it later this evening and center everything and work from there.I also have most of the components for your 208p arriving tomorrow,so I might just build up cards 7-9 and see how it behaves.

Remember there are two trimmers that affect the COs tracking together. Card 9 R5 and TR7.
Karl71
davebr wrote:
Karl71 wrote:
Yeah papz I spent a good deal of time matching the resistors.I went through every resistor I had to find the tightest values.Ithink the problem is with the trimmers.last week when I scoped card 8 CO out from the edge connectors It was good.I think the problem began when I started moving trimmers.Im going to sit down with it later this evening and center everything and work from there.I also have most of the components for your 208p arriving tomorrow,so I might just build up cards 7-9 and see how it behaves.

Remember there are two trimmers that affect the COs tracking together. Card 9 R5 and TR7.

Thanks Dave.I had tried yesterday evening with both those trimmers and the best I could get was the slow belly dancing waves.im thinking if I centre everything,all trimmers and start from a middle point I may be able to keep track of what is happening.I will be in touch if I exhaust the trimmer possibility.
Karl71
papz wrote:
From memory, the timbre trimpot setting also caused spurious oscillation in some builds. Try and adjust the timbre, waveform and card 9 trimpots together could help.

If the parallel resistors have the good value within 1% tolerance, they are not in cause.

Yip,its the timbre trimmer on the motherboard.its good now but i will continue this evening.
papz
thumbs up
bemerritt
so i was attempting to calibrate and noticed the bellydancing as I adjusted the CO waveshape trimpot.

here it is pretty stable



turn the trimpot too far and you get this



now, any ideas on how to get a better looking sine wave?[/video]
davebr
bemerritt wrote:
now, any ideas on how to get a better looking sine wave?[/video]

Yes, hand select Q1 for an Idss between 0.7 and 1.2. I personally just adjust resistors. Typically R41 on card8 will do the trick. I generally lower it and empirically find a value I like.

Dave
Karl71
davebr wrote:
bemerritt wrote:
now, any ideas on how to get a better looking sine wave?[/video]

Yes, hand select Q1 for an Idss between 0.7 and 1.2. I personally just adjust resistors. Typically R41 on card8 will do the trick. I generally lower it and empirically find a value I like.

Dave

I cant seem to dial out the instability.the best I can get is a very slow cycling.its apparent in the square wave stting.I tried swapping the 2n4339 but the ones I got from Utsource gave me a triangle output,no Sine.Ive ordered some from Samodular and hope to have them soon.I also have a small dimple in the top half of my sine.it causes uneven folding.I saw in another thread Tarandfeathers had a similiar issue and tracked it down to the 4016 on card 8.Im going to try replace that too.if nothing helps then I will try Daves resistor mod.
bemerritt
davebr wrote:
bemerritt wrote:
now, any ideas on how to get a better looking sine wave?[/video]

Yes, hand select Q1 for an Idss between 0.7 and 1.2. I personally just adjust resistors. Typically R41 on card8 will do the trick. I generally lower it and empirically find a value I like.

Dave


Thans dave. That and the trimmer on card 8 helped produce a perfect sine. Now just need to build up Papz's replacement boards to improve tracking and get my reverb tank bracket from electric music store.....

has anyone 3d printed one, as I have cad experience/access to one. If anyone can provide some dimensions ill send them a printed one!
Karl71
bemerritt wrote:
davebr wrote:
bemerritt wrote:
now, any ideas on how to get a better looking sine wave?[/video]

Yes, hand select Q1 for an Idss between 0.7 and 1.2. I personally just adjust resistors. Typically R41 on card8 will do the trick. I generally lower it and empirically find a value I like.

Dave


Thans dave. That and the trimmer on card 8 helped produce a perfect sine. Now just need to build up Papz's replacement boards to improve tracking and get my reverb tank bracket from electric music store.....

has anyone 3d printed one, as I have cad experience/access to one. If anyone can provide some dimensions ill send them a printed one!


Did you perform the trimmer mod?how far did you need to come down?
captnapalm
bemerritt wrote:
reverb tank bracket from electric music store.....

has anyone 3d printed one, as I have cad experience/access to one. If anyone can provide some dimensions ill send them a printed one!


I doubt a 3d printed bracket would hold up to the stresses. I can make some by hand (I have a sheet metal brake) if electricmusicstore doesn't come through soon.
bemerritt
Karl71 wrote:
bemerritt wrote:
davebr wrote:
bemerritt wrote:
now, any ideas on how to get a better looking sine wave?[/video]

Yes, hand select Q1 for an Idss between 0.7 and 1.2. I personally just adjust resistors. Typically R41 on card8 will do the trick. I generally lower it and empirically find a value I like.

Dave


Thans dave. That and the trimmer on card 8 helped produce a perfect sine. Now just need to build up Papz's replacement boards to improve tracking and get my reverb tank bracket from electric music store.....

has anyone 3d printed one, as I have cad experience/access to one. If anyone can provide some dimensions ill send them a printed one!


Did you perform the trimmer mod?how far did you need to come down?


Can check when i get home, i think i lowered the resistor by 20% or so and maxxed out the trimmer.
bemerritt
captnapalm wrote:
bemerritt wrote:
reverb tank bracket from electric music store.....

has anyone 3d printed one, as I have cad experience/access to one. If anyone can provide some dimensions ill send them a printed one!


I doubt a 3d printed bracket would hold up to the stresses. I can make some by hand (I have a sheet metal brake) if electricmusicstore doesn't come through soon.


Yeah, the 3d printed would just be a placeholder until the metal one arrives, but it can be quite strong with the right design. I have no doubt it will eventually come as the website comes under new "management". Not sure where you are located, but thanks for the offer on making one. I'll give it a little more time, as i would then need to get my money back as well. Any rough dimensions would be awesome tho.
bemerritt
Finally put it all back together and bam, sequencer and evelope generator arent putting any voltages out. LED's on the front panel are working. Open it back up and somehow, it appears my 12 volt power wire is sticking to the bottom of a daughter board.

I pull it off before i can even see what card it is. It looks like both of those two outputs go back to card 3. Sequencer to IC7, EG to IC 2. I switched IC1 and IC7 but didn't notice any change in performance.

Safe to say I fried all the IC's on the board? Relatively easy to just toss some new ones in, after I order them ofcourse. Any other ideas?

Really upset, but ultimately glad it wasn't worse.
needspeed
Anyway to find front panels at this point as having PCBs is great, but a front panel would be very helpful.....Thanks for any assistance.....Steve
Karl71
needspeed wrote:
Anyway to find front panels at this point as having PCBs is great, but a front panel would be very helpful.....Thanks for any assistance.....Steve


You could try papz.he sells them with his 208p pcb sets.
needspeed
Karl71 wrote:
needspeed wrote:
Anyway to find front panels at this point as having PCBs is great, but a front panel would be very helpful.....Thanks for any assistance.....Steve


You could try papz.he sells them with his 208p pcb sets.


Thanks will give it a go.....Steve
finson
Hi there, I have a problem with the pulser on my 208 r2.1. I can hear the pulses of the pulser on the phones while the monitor level is on zero! With lower pulser period, the single pulses turn into a audible sound. It seems the pulser modules transitions leak to the ground... This still occurs with a disconnected pulser LED.
Does somebody had/has the same problem with their 208, or has some idea what's wrong?
synthi
finson wrote:
Hi there, I have a problem with the pulser on my 208 r2.1. I can hear the pulses of the pulser on the phones while the monitor level is on zero! With lower pulser period, the single pulses turn into a audible sound. It seems the pulser modules transitions leak to the ground... This still occurs with a disconnected pulser LED.
Does somebody had/has the same problem with their 208, or has some idea what's wrong?

I´ve heard similar stories caused by not enoght juice in the PSU, you cold try powering the 208 with a bigger one...
doepferiano
happening to me too

the pulser clicks in the audio outputs, with volume to 0
the incredible thing is if I move the volume to 8 is going down

(the ENV too if in autoretrig mode)

finson wrote:
Hi there, I have a problem with the pulser on my 208 r2.1. I can hear the pulses of the pulser on the phones while the monitor level is on zero! With lower pulser period, the single pulses turn into a audible sound. It seems the pulser modules transitions leak to the ground... This still occurs with a disconnected pulser LED.
Does somebody had/has the same problem with their 208, or has some idea what's wrong?
dingebre
Hi everyone. Just coming to the Buchla world and Buchla SDIY projects. I just ordered the 218 PCB set from Roman. The BOM calls out a "microcontroller card" based on an STM32F405. The link in the BOM does not connect to this card and I can't find it on the site. Could some kind soul help me source the proper card?

Thanks
David
gruvsyco
dingebre wrote:
Hi everyone. Just coming to the Buchla world and Buchla SDIY projects. I just ordered the 218 PCB set from Roman. The BOM calls out a "microcontroller card" based on an STM32F405. The link in the BOM does not connect to this card and I can't find it on the site. Could some kind soul help me source the proper card?

Thanks
David


https://electricmusicstore.com/products/microcontroller-card
dingebre
Sigh... I totally missed that on the products page. Thank you very much.

David
dingebre
tarandfeathers wrote:
Envelope sustain boards are now up for sale, along with various other 208/Buchla odds and ends, at http://www.dunningtonaudio.co.uk

[...]

I'm writing an article that goes into some depth about the design of the envelope generator, the nature of the problem and how it is fixed. That should be up in a couple of weeks, for anyone who is interested.


Hello all. Just coming into this build, a bit late, I know. I was wondering if there is another source for "tarandfeathers" envelope sustain board? His site appears to be out of stock and I've not found information about any additional runs.

Or, does someone want to sell me one? PM if you have a spare you don't mind selling.

Thanks!

David
muncky
See here:
https://www.muffwiggler.com/forum/viewtopic.php?t=203257
dingebre
Many thanks.

David
trimix
I may be over-analysing at this point, but is there a preferred way to test each card for proper function before hooking up the whole enchilada and adding power?
When I do eurorack builds I test each module out of the rack, on my bench. But has someone come up with a test rig or setup to test, for example, card #8 on its own? Or do you plug it into the mother board and see if it functions at all?
wedaman
Hello everyone.
I ask questions here because I can not find the build thread of Buchla 211.

I built the POWER SUPPLY UNIT MODEL 211.
However, the +15V terminal has only 11.75 voltage.
Does anyone know the information on the circuit diagram of Buchla 211 ?

I post a photo.
Please give me advice.

captnapalm
wedaman wrote:
Hello everyone.
I ask questions here because I can not find the build thread of Buchla 211.

I built the POWER SUPPLY UNIT MODEL 211.
However, the +15V terminal has only 11.75 voltage.
Does anyone know the information on the circuit diagram of Buchla 211 ?

I post a photo.
Please give me advice.


the 15V is supplied by IC3. All the problems I've seen with these have come from a blown or improperly soldered IC3.
wedaman
captnapalm wrote:
wedaman wrote:
Hello everyone.
I ask questions here because I can not find the build thread of Buchla 211.

I built the POWER SUPPLY UNIT MODEL 211.
However, the +15V terminal has only 11.75 voltage.
Does anyone know the information on the circuit diagram of Buchla 211 ?

I post a photo.
Please give me advice.


the 15V is supplied by IC3. All the problems I've seen with these have come from a blown or improperly soldered IC3.


captnapalm, Thank you for your support.
I will check the IC3.
wedaman
wedaman wrote:
captnapalm wrote:
wedaman wrote:
Hello everyone.
I ask questions here because I can not find the build thread of Buchla 211.

I built the POWER SUPPLY UNIT MODEL 211.
However, the +15V terminal has only 11.75 voltage.
Does anyone know the information on the circuit diagram of Buchla 211 ?

I post a photo.
Please give me advice.


the 15V is supplied by IC3. All the problems I've seen with these have come from a blown or improperly soldered IC3.


captnapalm, Thank you for your support.
I will check the IC3.


I checked IC3 and re-soldered, but I could not get +15v.
IC3s Pin11 outputs -15 v.

I can not find a circuit diagram and I can not repair it.
Throw my hands up.
captnapalm
wedaman wrote:


I checked IC3 and re-soldered, but I could not get +15v.
IC3s Pin11 outputs -15 v.

I can not find a circuit diagram and I can not repair it.
Throw my hands up.


I was wrong before. It looks like IC3 only makes -15.

The only places I could find +15 on mine are on one side of R4 and one side of D1 and that area.

My suspicion is that it takes +12V and +5V and adds them together, then uses resistors to trim it down to +15.
davebr
captnapalm wrote:
wedaman wrote:


I checked IC3 and re-soldered, but I could not get +15v.
IC3s Pin11 outputs -15 v.

I can not find a circuit diagram and I can not repair it.
Throw my hands up.


I was wrong before. It looks like IC3 only makes -15.

The only places I could find +15 on mine are on one side of R4 and one side of D1 and that area.

My suspicion is that it takes +12V and +5V and adds them together, then uses resistors to trim it down to +15.

I have no information and don't have one to look at easily but the LM27313 is a boost regulator so I believe it is used to step up the +12V to +15V. From a quick look at the datasheet the bandgap reference is 1.23V and I see a 13K3 resistor in the BOM. Working backwards, that would require a 148K9 resistor for the other resistor and there is a 150K in the parts list. Check these resistor values and soldering around these parts.

Dave
jersupereq
I'm having an issue where noise slowly builds up until it drowns out the oscillators. I believe its related to card 12 where ic4 is heating up like crazy. I can't find any shorts or errors on the card. The soldering is ugly i know seriously, i just don't get it


[/img]
davebr
jersupereq wrote:
I'm having an issue where noise slowly builds up until it drowns out the oscillators. I believe its related to card 12 where ic4 is heating up like crazy. I can't find any shorts or errors on the card. The soldering is ugly i know seriously, i just don't get it

IC4 is getting hot because it is oscillating. That is also the source of the noise. Those LM380s can go unstable quite easily. Check all the component values around that part and make sure the soldering is good. Lots of different things can make them oscillate so you just have to check everything. They will burn themselves out so I wouldn't leave it powered on for long.

Dave
jersupereq
davebr wrote:
jersupereq wrote:
I'm having an issue where noise slowly builds up until it drowns out the oscillators. I believe its related to card 12 where ic4 is heating up like crazy. I can't find any shorts or errors on the card. The soldering is ugly i know seriously, i just don't get it

IC4 is getting hot because it is oscillating. That is also the source of the noise. Those LM380s can go unstable quite easily. Check all the component values around that part and make sure the soldering is good. Lots of different things can make them oscillate so you just have to check everything. They will burn themselves out so I wouldn't leave it powered on for long.

Dave


You were right I spotted an incorrect cap value on the motherboard right next to card 12, no more noise or overheating. Thanks! thumbs up Next bug to figure out is the pulser not running only stepping with the switch, but now is time to sleep. Dead Banana
trimix
Papz, I'm just now calibrating (or trying to) my two pA726 adapters.
The trim pots seem to do nothing....
And the last comment on your build sheet states, "The voltage should be around 0.63V" uh, where?

Also when testing board 6 (with no other boards mounted on the Motherbd) the ca3046 gets really hot at the top end....normal? Board 7 not at all.
I've checked component placements and soldering all looks good, no obvious shorts. I guess I just don't know what I should be seeing as normal
papz
The voltage should be measured with the red probe on the pA726 "T° Volt" pad next to the trimpot and the black probe on the 208's ground.

The trimpot works with the jumper in place only, first measure without jumper and then with jumper to adjust voltage 60mV below the first reading. If it doesn't change voltage, double check resistors value and solder joints.

The 3046 should get hot, that's how thermal oven compensation works.
If it stays cold, there is a problem, faulty IC or bad solder joint or bad connection with the 208 card...
gruvsyco
Some questions.

Should the frequencies on the panel be fairly close to real? My pitch goes way below 55 and way above 1760.

My CO tracks the keyboard at 2v/o but not at all on 1 or 1.2. No matter the adjustment, the range is not wide enough. The MO has the same problem except it doesn't even track on 2v/o. Should the MO track the keyboard at all?

My timbre/waveshape circuit (slider) seems to be full at around 3-4. I'm guessing the knob on that circuit is supposed to morph the waveform from sine to whatever the waveshape selected is. If this is the case, my knob seems to give the best waveforms at around 50%.
papz
This should help http://www.portabellabz.be/images/208/208%20build%20notes_final.pdf
wedaman
Hello everyone.
I need help.

I removed the flux. And I confirmed soldering with a loupe.

I can not hear anything from card 6. Which pin of molex is the MO output of card 6?

And there is sound from card 7. However, moving the FINE TUNING knob and the PITCH slide does not change the sound.
Where is pitch adjustment on card 7?

I used pA726.
trimix
I'm working on a few issues... but before I get into those, I wonder if I'm connecting my scope incorrectly...
- I have the probe connected to the output jack leads at the top of the motherboard.
- Output knob all the way CW, Headphones all the way CCW, Preamp level sliders all up, Output channel pots A and B both CW, preamp switches to VCA


The first 5 cards are working really well, Mod oscillator is responding to inputs, but only on AM modulation... and I don't seem to get anything from there on. I do hear a low level output from the mod oscillator, so I'm fairly sure card 5 and 6 are good, but 7/8/9 are (maybe) not outputting. Working on that.

But I want to make sure there isn't a better way to read the output. I would clip the scope to the output pins of the card directly, but because these boards are so interdependent, that wouldn't help
wedaman
wedaman wrote:
Hello everyone.
I need help.

I removed the flux. And I confirmed soldering with a loupe.

I can not hear anything from card 6. Which pin of molex is the MO output of card 6?

And there is sound from card 7. However, moving the FINE TUNING knob and the PITCH slide does not change the sound.
Where is pitch adjustment on card 7?

I used pA726.


I found the schematic. I try to solve it myself.
Thanks. lol
papz
Hi

Are your pA726 good working ? The 3046 should warm up.
The MO is not audible if in low frequency or not properly routed to the LPG2 (signal routing switch in the middle position). Does it modulate the CO when you push the index slider up with the modulation switch set to am of fm ?

The trimmers location is on https://modularsynthesis.com/roman/buchla208v2/208spss.htm
The pA726 calibration instructions on http://www.portabellabz.be/images/pa726/pa726-208.pdf
The schematics on http://www.portabellabz.be/images/208/schemas_208.zip
The 208 calibration instructions and build notes on http://www.portabellabz.be/images/208/208%20build%20notes_final.pdf

Monitoring at the output jacks is ok and what I do but don't do it with all levels all the way up to avoid distortion.
trimix
papz wrote:


Are your pA726 good working ? The 3046 should warm up.
.

Thanks for responding, Papz

I have 4 of the pa726 boards assembled. One is working in Board 6, although I get very little change with the trimmer. I'm not fully satisfied with that, but the 3046 on card 6 is heating up. (seems at one end only however). That's what I thought was a problem at first. I used a TL071 instead of TL061 on all boards

Ive tried the remaining 3 pa726 on card 7, which just stays cold. Trimmer does nothing. I've also swapped the 3046 onto/from the working (?) pa726 and no change, but card 6 still seems to be working the same. I've taken 3046 from the unused boards and swapped them around too. I get different readings at the T* but again the calibration procedure is ineffective so far. So I don't think it's to do with the pa726.
I was very careful to check every joint on Card 7 - no shorts... clean pads; every component is oriented correctly and in the right place. I lifted legs and checked resistors (all 1% or better) and all caps. I swapped the 4136's for new ones, changed the tranny. Molex pin #18 gives me -15v and #17 shows +15v... of course #16 for Q ground and #15 for Noisy ground. The other ones going between boards I have no idea what should be the readings.

The exception to the overall build is the LM301's - no dip8 was available, so I have an SOIC8 on an adapter board in its place throughout the build, including on card 6. That can't be the problem could it? Orientation and contacts have been checked.

So I'm kinda stumped at this point - I've did my due diligence before reaching out for help, but help is welcome. Until the pa726 issue is confidently resolved, I don't feel I should continue the remaining calibrations. It's like card 7 is just dead. I even sprayed cold canned air onto the card to see if there were any warm spots - it just stayed frosty all over!

I'm going to dive into the motherboard tonight, but don't expect to see anything there, because I'm getting voltages on the Molex pins in every position.

I've looked thru all the links you provided, and I'm up with all the changes you suggested , along with those of Dave Brown and Don T.
papz
DIP8 LM301's are easy to find. I got some from this seller which are ok https://www.befr.ebay.be/itm/LM301AN-Amplificateur-operationnel-DIP-8- National-RoHS-Lot-de-5/181746393780?hash=item2a50ede2b4:g:XIsAAOSwFO5a FtRu
I'd replace the SOIC8 ones with these to exclude this as a possible cause.

TL061, TL071, TL081 work on the pA726.
To exclude the pA726 as a cause, you can replace it with a pair of NPN such as 2N3904 (check the µA726 datasheet for pinout) or the SSM2212 adapter for test purpose.
trimix
Will do - thanks. It will take a couple weeks for all the replacements to arrive (also ordered more cd3046) and in the meantime I have another set of PCBs to assemble. I'll see if the second batch have the same problems
Sammus
I got a rare parts kit from boops a little while ago and finally have just opened to use. My kit contains two "7994659 SGS 17026" in place of the MC846P.



I can't anything on the internet at all about that part number - just checking, is it an equivalent part? (and not an error in packing)?

Cheers

Edit: confirmed by boops to be the mil spec version
dingebre
Question re: 218r power. Is the ground on the V2 PCB connected to clean or noisy ground? Or, more likely, am I missing the painfully obvious again...

David
wedaman
Please someone give me some advice.

I have problems with MO.

When the routing switch is centered, the sound of CO can be heard from the output, but the sound of MO is very small at output.

The MO signal reaches the Molex pin 9 of the card 11 from the Molex pin 4 of the card 6 via R 84 (120 K ohm) of the mother board.

I confirmed with the scope that the signal was coming up to R 84. However, the signal becomes weak after R 84 and the waveform is also very small.

Are these correct? What is the function of R84?
papz
Does the MO work as a modulation source ? You can check it with the index section and the mod CV out.
If it works, the problem is likely not in the MO but in the LPG2, on card 11, or in the modulator, on card 5.
You can check the LPG2 with another source : external signal patched to the preamp, with the routing switch in top position, or LPG1 output with the routing switch in bottom position.
wedaman
papz wrote:
Does the MO work as a modulation source ? You can check it with the index section and the mod CV out.
If it works, the problem is likely not in the MO but in the LPG2, on card 11, or in the modulator, on card 5.
You can check the LPG2 with another source : external signal patched to the preamp, with the routing switch in top position, or LPG1 output with the routing switch in bottom position.


Thanks, papz.

I confirmed the mod CV out (pin 11) of card 6 with the scope.
The voltage of pin 11 is DC 4.93 V.
And the voltage of pin 4 is AC 0.668 v.
Card 6 does not seem to work well.

The pA 726 has been calibrated. The soldering has been reconfirmed and the value of the part has been reconfirmed.
Do you have any advice?
papz
I meant the mod CV out banana socket in the top right of the panel.
Can you patch it to a CV input, such as CO pitch or other, and check if it modulates ?

Can you also check if pushing the MO index sliders up modulates the CO pitch (FM) or amplitude (AM) depending on the modulation switch position ?

Also if there's signal on the channel B with the signal routing switch in the lowest position, both LPG1 and LPG2 sliders to 10 and channel A pot to 0 ?
wedaman
papz wrote:
I meant the mod CV out banana socket in the top right of the panel.
Can you patch it to a CV input, such as CO pitch or other, and check if it modulates ?

Can you also check if pushing the MO index sliders up modulates the CO pitch (FM) or amplitude (AM) depending on the modulation switch position ?

Also if there's signal on the channel B with the signal routing switch in the lowest position, both LPG1 and LPG2 sliders to 10 and channel A pot to 0 ?



Thanks for your advice, papz !
I tried it in your way.

I connected a patch from the CV out at the top right of the panel to the CO pitch input.


This is the result.

<balanced external>
I moved MO index sliders up, but it does not change.

<a.m.osc>
I moved the MO index sliders up. The sound of CO gradually became smaller. It is not completely quiet.

<f.m.osc>
I moved the MO index sliders up. The pitch of CO gradually down.


Also, when the routing switch is in the lowest position, both LPG1 and LPG2 sliders to 10.
The sound of channel A becomes smaller, but it does not quiet completely. And channel B became completely quiet.

What is wrong?
Peake
Balanced External is the vactrol "ring modulator" which requires an external signal into the Preamp Aux In jack and the Gate 2 Source switch all the way up and Gate 2's level up as well...
papz
The MO seems working. If you increase the MO frequency, does the CO pitch and amplitude modulation well get faster ?

The issue is probably related to LPG2.
Does the LED light up if you push the LPG2 right slider up ?

You don't seem very familiar with how the 208 works or should work. Do you have the manual ? https://drive.google.com/file/d/0BwtXQvT4dT5hVkpqeDJCMS1fYmM/view?usp= sharing
Sammus
I also have a potential issue with my MO I haven't managed to track down yet.

The MO output looks perfect and seems to modulate as expected, but when I look at it on a scope the CV output and the main output through the LPG looks very different. With MO set to square, the CV out is a nice perfect square wave. Through the LPG (fully open), the voltages decay toward zero, so they're kind of slopey looking squares. At high frequency it looks like a square still, but as the frequency drops the decay becomes very apparent.

I haven't done much troubleshooting at all, and start poking around when I get a chance, but any pointers would be much appreciated.
tarandfeathers
Sammus wrote:
I also have a potential issue with my MO I haven't managed to track down yet.

The MO output looks perfect and seems to modulate as expected, but when I look at it on a scope the CV output and the main output through the LPG looks very different. With MO set to square, the CV out is a nice perfect square wave. Through the LPG (fully open), the voltages decay toward zero, so they're kind of slopey looking squares. At high frequency it looks like a square still, but as the frequency drops the decay becomes very apparent.

I haven't done much troubleshooting at all, and start poking around when I get a chance, but any pointers would be much appreciated.


This is normal behaviour. The audio output amplifiers are capacitively coupled so they will not pass the DC components of the square wave.
Sammus
tarandfeathers wrote:
Sammus wrote:
I also have a potential issue with my MO I haven't managed to track down yet.

The MO output looks perfect and seems to modulate as expected, but when I look at it on a scope the CV output and the main output through the LPG looks very different. With MO set to square, the CV out is a nice perfect square wave. Through the LPG (fully open), the voltages decay toward zero, so they're kind of slopey looking squares. At high frequency it looks like a square still, but as the frequency drops the decay becomes very apparent.

I haven't done much troubleshooting at all, and start poking around when I get a chance, but any pointers would be much appreciated.


This is normal behaviour. The audio output amplifiers are capacitively coupled so they will not pass the DC components of the square wave.


Sweet, I had a slight inkling that may be the case, but not confident enough to make any assumptions. Everything seems fine, in that case smile thanks for putting my mind at ease.
wedaman
papz wrote:
The MO seems working. If you increase the MO frequency, does the CO pitch and amplitude modulation well get faster ?

The issue is probably related to LPG2.
Does the LED light up if you push the LPG2 right slider up ?

You don't seem very familiar with how the 208 works or should work. Do you have the manual ? https://drive.google.com/file/d/0BwtXQvT4dT5hVkpqeDJCMS1fYmM/view?usp= sharing



When I increase the MO frequency, the CO pitch did't amplitude modulation well get faster.

The LED light up when I pushed the LPG2 right slider up.

Thank you for letting me know the link of the manual.

I will check LPG 2 (card 11) again.

I know that it is important that vactrols values match.
What do you think about the resistance value of vactrols? Which is the higher or lower resistance value recommended?
papz
The vactrols matching is not related to this issue.
Vactrols faults are rare and since the panel LED lights up I wouldn't suspect a dead one at first.
Their resistance should be infinite or very high (several Mohms) with the slider to 0 and between around 1K and 1.5K with the slider to 10, measured installed on the board, with the module powered.

Check or replace ICs on board 11 and IC3 on board 5.
4016 and 4136 are usual suspects.
If this doesn't help, check Q1 2N4340 on board 11.

And of course double check the solder joints for a bad one or a bridge, components values and orientation, headers solder joints...
wedaman
papz wrote:
The vactrols matching is not related to this issue.
Vactrols faults are rare and since the panel LED lights up I wouldn't suspect a dead one at first.
Their resistance should be infinite or very high (several Mohms) with the slider to 0 and between around 1K and 1.5K with the slider to 10, measured installed on the board, with the module powered.

Check or replace ICs on board 11 and IC3 on board 5.
4016 and 4136 are usual suspects.
If this doesn't help, check Q1 2N4340 on board 11.

And of course double check the solder joints for a bad one or a bridge, components values and orientation, headers solder joints...



I checked, but vactrols had no problem.

I replaced ICs on board 11 (4066 and 4136), IC 3 (4066) on board 5 and Q 1 2N4340 on board 11.

But there was not any change. Probably this condition will be normal for my 208.
I will calibrate next.

By the way, I am reading the Easel manual in Google Translate. There are many pages!

Papz, thank you for your support.
papz
You're welcome.

If the LPG2 / channel B outputs no signal, I'm afraid this condition is not normal, definitely. wink
wedaman
I'm asking about 5 pots of 208 mother board.
I am using the following pots.

CHANNEL B (A100K)
CHANNEL A (A100K)
REVERB LEVEL (B100K)
MONITOR LEVEL (A100K)
OUTPUT LEVEL (A100K)

However, I noticed it when I saw the DAVE's site. https://modularsynthesis.com/roman/buchla208v2/208%20Motherboard%20fro nt.png
The 50K pots is used.
Please tell me the value of your POT.
Is 100K OK?
papz
Any value from 10k to 100k is ok but a faulty channel B pot could also be a cause.
With a signal routed to LPG2 fully open, you can check for signal with the scope from card 11 pin 3 and trace it untill card 12 pin 11 via the pot and R71 33k resistor on the MB.
wedaman
papz wrote:
Any value from 10k to 100k is ok but a faulty channel B pot could also be a cause.
With a signal routed to LPG2 fully open, you can check for signal with the scope from card 11 pin 3 and trace it untill card 12 pin 11 via the pot and R71 33k resistor on the MB.


I checked, but the above case is no problem.


There seems to be a problem with IC 2 (4066) of card 5.
When I checked by the scope, the signal of MO is coming up to pin 8 of IC 2. However, the waveshapes from pin 9, pin 10, and pin 13 of IC 2 are small and distorted.
I replaced the IC 2, but it was not improved.

Any advice is welcome.
papz
Sorry but your descriptions and answers to my questions are not clear. This makes it very difficult to figure out what happens and help you.

What do you mean by "the above case is no problem" ?
Are the LPG2 and channel B working ? Could you trace the signal as I told you ? Which signal was it ? MO ? CO via LPG1 ? External ?
From your previous posts, I understood this output is not working but the MO works as a modulation source.

Can you post pics of your cards and of the oscilloscope displays, detailing where it was measured and the related panel settings ?
wedaman
I'm sorry for the late reply.

papz wrote:
Any value from 10k to 100k is ok but a faulty channel B pot could also be a cause.

When I checked with the scope, channel B pot is working.
Because, when channel B pot is CCW, the waveform becomes horizontal. And CW, the height of the waveform becomes maximum.


papz wrote:
With a signal routed to LPG2 fully open, you can check for signal with the scope from card 11 pin 3 and trace it untill card 12 pin 11 via the pot and R71 33k resistor on the MB.


I traced the MO signal.
The routing switch is centered, LPG 2 and channel B pot are fully opened.


The following are the images of the scope of each part.

at card 11 pin 3.



at channel B pot center pin on MB (fully opened).



before R 71 33 k resistor on the MB.



after R 71 33 k resistor on the MB.



at card 12 pin 11.



I think there is a problem with R 71 33 k resistor. But R 71 is a correct value.



I would like to ask your opinion.
Any advices are welcome.
papz
With the routing switch in central position, this sine wave is a bit surprising : the MO has no sine output. It looks like it's the CO output.
Is the routing switch good working ? The IC related to this switch is IC1 on card 11.
tarandfeathers
papz wrote:
With the routing switch in central position, this sine wave is a bit surprising : the MO has no sine output. It looks like it's the CO output.
Is the routing switch good working ? The IC related to this switch is IC1 on card 11.


I don't think the MO is producing any output (or it is not making it through the switches on the modulator), according to the scope traces that sine wave is over 28kHz so something in the MO signal path is unstable and oscillating. There shouldn't be any signal on the scope at card 12 pin 11 anyway, this is right on the inverting input of an op amp whose non-inverting input is tied to ground - an op amp always tries to keep its inputs equal so it uses its output to force the inverting input to ground as well.

Is there anything more sensible looking on card 6, pin 4? The signal levels mentioned earlier sound low to me, there should be around 7.5Vp-p at this point, wedaman reported getting only around 0.67V?
papz
Thanks tarandfeathers. 28kHz is high for the CO indeed.

Wedaman wrote the MO modulates the CO as it should, so the CV output is working and I assumed the signal output it's taken from is thus working as well, but it's good to doublecheck indeed.
wedaman
Thanks Guys.

I swaped IC 1 of card 11 five times. Is it still necessary to swap?
Do you know how to check whether the IC is OK or error?


These are waveshape images of card 6 pin 4.
I have not calibrated yet. sorry.

It's saw.



It's rectangle.(I understand not square, haha )


It's triangle.



Please let me know what you think.
Any advice will be of help to me.
tarandfeathers
Although the shapes and amplitude are approximately correct, the frequency is well outside the range of what the MO should be producing. Where were the frequency slider and fine tune pot set when these images were taken?

I think you need to remove card 6 and double and triple check all solder joints and values, maybe post photos? If you can get the card operating in the correct range then the waveshapes should be much better formed.

The LPG and output amplifier are almost certainly working okey, but the signal coming from the MO is completely out of band and will not be passed (it is low pass filtered to the sine-like wave you posted earlier), plus it is outside the range of human hearing so you wouldn't hear it anyway.
wedaman
tarandfeathers wrote:
Although the shapes and amplitude are approximately correct, the frequency is well outside the range of what the MO should be producing. Where were the frequency slider and fine tune pot set when these images were taken?

I think you need to remove card 6 and double and triple check all solder joints and values, maybe post photos? If you can get the card operating in the correct range then the waveshapes should be much better formed.

The LPG and output amplifier are almost certainly working okey, but the signal coming from the MO is completely out of band and will not be passed (it is low pass filtered to the sine-like wave you posted earlier), plus it is outside the range of human hearing so you wouldn't hear it anyway.


Hi tarandfeathers,
I appreciate your precise advice.
The frequency of MO is out of range. I understood.
Certainly the sound of my MO is like a mosquito sound.
I will go back home and check double triple card 6.
I will post the results.
papz
According to these previous reports the MO is able to oscillate at LFO rate. The out of range is likely due to a wrong setting of its preset and range trimpots on the MB.
I wonder if it's not a user problem rather than an electronic issue.

wedaman wrote:
<a.m.osc>
I moved the MO index sliders up. The sound of CO gradually became smaller. It is not completely quiet.

<f.m.osc>
I moved the MO index sliders up. The pitch of CO gradually down.


wedaman wrote:
When I increase the MO frequency, the CO pitch did't amplitude modulation well get faster.
tarandfeathers
You could also interpret those comments as meaning that the sound of the CO changes as the index slider is moved, but does not necessarily continue changing when the slider stops moving. Even with external CV, I'd be surprised if you could get the Mo up to that frequency in normal circumstances.
papz
Unlike the CO that is limited to about 2.5 kHz the MO is able to oscillate at high frequency above the audio range. On my 208, properly calibrated, I can drive it up to 30 kHz using the ToolBox frequency switch and panel input together as CV sources.
tarandfeathers
papz wrote:
On my 208, properly calibrated, I can drive it up to 30 kHz using the ToolBox frequency switch and panel input together as CV sources.


No doubt, but I wouldn't describe that as "normal circumstances" when troubleshooting a suspect module :wink:
papz
Indeed, but with the panel settings and trimpots all the way up, I wouldn't be surprised if the MO oscillates at 30kHz, I won't uncalibrate mine for test purpose only though wink

Improper calibration and panel settings upset effective troubleshooting, so we're likely not under "normal circumstances".

Hence my wondering regarding a user error :
- if the MO oscillates above the human ear audible range, it's normal not to hear it
- some measures, descriptions and answers of Wedaman are incomplete, vague, wrong or contradictory
- Wedaman doesn't seem to have a very clear idea of how the 208 works and what it's supposed to do
wedaman
Sorry, my English is not good.
Wait a while for the results. hyper
wedaman
I checked card 6 three times. But the sound of MO is like a mosquito sound.
I didn't swap only Q1 (2N4341) of card 6. I will swap as soon as parts arrive from mouser.

They are the images of card 6.
[img][/img]

[img][/img]


pa726.
[img][/img]

[img][/img]


Also the images of card 11.
[img][/img]

[img][/img]


Do you have any advice?
Thanks.
papz
What are the panel settings when the MO sounds like a mosquito ?

C4 on card 11 looks very big for a 1µF cap, should be the same as C5.
Same for card 10 just in case.
Sammus
papz wrote:
What are the panel settings when the MO sounds like a mosquito ?

C4 on card 11 looks very big for a 1µF cap, should be the same as C5.
Same for card 10 just in case.


C4 on card 11 is likely swapped as per the recommended mod on https://modularsynthesis.com/roman/buchla208v2/208spss.htm

Quote:
The MO is mixed to the signal output through C4 on Card 11. This is a 1 µF capacitor feeding a 10K potentiometer which is a high pass filter with a lower frequency cutoff of 15 Hz. I increased C4 to 47 µF with a capacitor on the rear of the card where there is more room. This allows lower frequency MO output to be passed through on the signal outputs. This scope image shows the mixing of a low frequency MO triangle with a high frequency CO which is not possible with the original 1µF capacitor.
papz
Thanks for the info, I didn't know this mod, the latest time I checked Dave's page in details was long ago.
wedaman
This movie is the MO sounds like a mosquito.
https://youtu.be/wrGz6U-hMk0

The channel A level is 2.5 but the channel B level is 10.
The channel B is very small sound.

Do you have any advice?
Thanks.
tarandfeathers
I think I have heard that people with fake uA726s found that their oscillators produced extremely high frequencies (relatively speaking). Perhaps there is a build error with the pA726 on the MO card or a faulty CA3046? You can try replacing the sub module temporarily with two 2N3904 (or any generic NPN transistor) and see if this improves the behaviour - tracking/temperature stability won't be good but it should oscillate at the correct frequency.
wedaman
tarandfeathers wrote:
I think I have heard that people with fake uA726s found that their oscillators produced extremely high frequencies (relatively speaking). Perhaps there is a build error with the pA726 on the MO card or a faulty CA3046? You can try replacing the sub module temporarily with two 2N3904 (or any generic NPN transistor) and see if this improves the behaviour - tracking/temperature stability won't be good but it should oscillate at the correct frequency.


Thanks tarandfeathers.
I have 2N3904s. I try your excellent advice ! hyper
Sammus
Hi!

I just finished casing my 208r build, almost everything is perfect, except the pulser doesn't trigger from the keyboard!

1) I have read Dave Brown's guide, and have install the missing link from SW8 to SW10 which I think is meant to solve this exact issue:
Dave Brown wrote:

A 218 V1 will sometimes not trigger correctly as the pulse output is only about 6V. You can parallel a 240K resistor across R56 on the back of the motherboard to change the pulse in threshold from 10V to 5V. This changes the threshold for the Pulser, Sequencer, and Envelope Generator. However, the Pulse input will NOT trigger the pulser when Keyboard is selected. There is a run missing to SW10. Add a wire on the motherboard rear between SW8 and SW10 as shown below.


2) 218 I'm using is a V2 with a "proper" pulse output, and the pulse successfully triggers the envelope and steps the sequencer if set to.

3) I have checked the pulser switch continuity as per the part number, and it is functioning as it should. I checked all before installing them, and then again now I have noticed this issue smile

4) Double checked panel settings smile the bottom pulser switch is is set to "triggered" and the top one is set to "keyboard".

Any guidance here would be much appreciated! thanks!
kashmir
Hello everyone,

I was extensively calibrating my recently finished 208 (big thanks to all builders for sharing the tips and mods!) and I was wondering how should the timbre circuit perform. I'm able to get enough of folds and have no unwanted oscillations but still there are some "pops" in the sound when increasing timber slider at higher frequencies. On the scope the waveform is smoothly shaping and then suddenly jumps forward a bit, it is usually at the moment when the rising peak is changing to dip. This happens more with higher frequencies (say 500hz above) and higher slide range (6-10). It pops usually 2 3 times between 6-10 on the slider and always at the same spots so it is not random. I tried different resistor changes on various recommended places and all possible calibrations, but the combination of few folds+higher pitch+ strong timbre always causes it.

Is this behavior usual or the timbre can work smoothly at all settings?

Another thing that no one mentioned is that the spring reverb oscillates a lot, sometimes it howls really loud, so no speakers or headphones are needed to hear the easel smile anyone has simillar issue?
keithwin
Hi All,

Looking to buy a Music Easel Infinite Sustain Module by Dunnington Audio, anyone got a spare?

Many thanks

Keith


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