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WIGGLING 'LITE' IN GUEST MODE

Buchla 208r V2.1 (Blue) Build Thread
MUFF WIGGLER Forum Index -> Music Tech DIY Goto page Previous  1, 2, 3, ... 20, 21, 22  Next [all]
Author Buchla 208r V2.1 (Blue) Build Thread
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.
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