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208p build thread (papz's PCBs)
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Author 208p build thread (papz's PCBs)
papz
FAQ
Buildnotes and calibration
(Build notes for the early "promotional offer" revision)
Parts layout
Schematics

Happy building !
the bad producer
thumbs up
papz
I updated the cards pics with components layout and values and the build notes.
The C5 47µF tantalum cap mentioned in the BOM works fine in the CO instead of the 56µF.
R45 100k instead of 20k eases tracking calibration.
Karl71
this is gonna be good. hyper looking forward to a thread of well documented success stories.
papz
Me too for sure ! lol
beautyofdecay_
I started my build today and populated the motherboard.
I have to wait for the cards components before I can continue...

papz
thumbs up
papz
Some extra infos added in the build notes.

It's better to match the vactrols on boards 10 and 11, or use dual VTL5C3/2.

Vactrols VT4 and VT2 on board 5 need to be selected on test for proper AM performance.

On board 7, R3 should be selected on test, a value between 3k8 and 12k, depending on the vactrol, to set the desired timbre amplitude. I find 4-5 folding is good, as shown on http://modularsynthesis.com/buchla/208/buchla_208.htm but others prefer more foldings. It's up to the builder to select what best suits his needs.

On board 8 the 2N4399 needs selection on test for proper sine waveshape.

I think this depends not only on the part itself but on the other parts in the circuit as well, therefore I use to select parts on test directly in each circuit.
pathein
thanks for the updates

I have just received the pcbs and panel. Got to say that the panel is really looking good. Next up will be waiting for the various parts to arrive, cant wait to start working on it
papz
Thanks for the feedback Chugging Beers
pathein
hi papz, some questions regarding the pA726 board. For the electrolytic, is it necessary to get at least 35v rating type or 25v type depending if its +-12v/+-15v?

for tab 1/1tab, it will be populated with male pin header?

for the resistors, will 1/10w rating be ok or stick to 1/4w type?
papz
25V is ok for the electrolytics, these are between each +15V/-15V/+10V rails and ground. But higher voltage is ok, I generally use 50V since I mostly stock these, are the same size and price as 25V and can do more. Also, the higher the voltage rating, the longer the life expectancy.

I'd rather use 1/4W resistors.

The DIP10 emplacements are to connect the pA726 to the boards, vertical one to 6 and horizontal one to 7.
I'm not sure the holes are large enough for headers.
I simply use thick components legs, there are much more than needed when building a 208. lol
"1" shows the µA726's pin 1, "tab" the µA726's tab/pin 10.
The trimpot should be on the same side as the other trimpots, this way you can't be wrong.
More details and pics on http://www.portabellabz.be/pa726.html
pathein
Cool, thanks for the info, much appreciated!
heapish
Has anyone done a mouser cart for this?
beautyofdecay_
papz wrote:
Some extra infos added in the build notes.

It's better to match the vactrols on boards 10 and 11, or use dual VTL5C3/2.

That's a good idea.
I think a VTL5C3/2 should work like this? The vertical blue line is a wire link.



The wires of the original VTL5C3/2 are long enough to connect the vactrol this way. I don't know about the current clones however...
papz
Or this way.
Legs can be extended with wire if needed.

sanemalkavian
Hi everyone. I am new at this, so not sure how good it is.

I compiled a Mouser project based on the BOM lists from PDFs. Mouser project has all the components that can be found based on those BOMs, so parts that are rare and cannot be found on mouser, including sliders, pots and hardware parts are not included.

I also included everything needed for pA726 except for CA3046 and two pin header.

In the attachment are all Excel files generated from PDFs, including a compiled mouser cart, where all parts that are not in stock are replaced with other part number. Compiled Excel doesn't include parts needed for pA726.

I hope this will help.

Mouser project 208
beautyofdecay_
I think there is a mistake in your BOM (I made the same mistake... eek! )
You should order CD4016, not CD4066!

The original BOMs from Roman specifies the CD4066. Check the PCB layout pictures from papz (or the original Buchla schematics). There only 4016s are used.

EDIT: checked the datasheets and the 4066 can be used also as it is an updated version of the 4016... Sorry for the confusion!
sanemalkavian
Thank you for the info. I used the recommendations from papz, as he says that 4066 can be used, except for card 8, where 4016 is recommended for IC2, so BOM contains 1 4016.
papz
Thank you sanemalkavian thumbs up

Some 4016 may cause problems indeed, which can be avoided using 4066 instead. I now use 4066 in all my 208 builds.
In case some wonder whether this affects the sound, the answer is no, these ICs are used to voltage control switches.
papz
Some builders ask me about this on the promo PCBs card 8.



The trace touched the eyelet and was rectified at last minute, but the solder mask wasn't rectified.
So no worries, it is ok and can be used as is.
beautyofdecay_
Making progress...

Card 1, 2, 3 and 4 are up and running cool
papz
thumbs up

trimix
Since I can't seem to find anyone offering panels for the 208 right now, I was wondering if anyone has drawing files (especially drilling centres) for the 208.
Formats can be .svg .ai .dxf ... anything editable.
I'm not looking to make a clone... I actually want to customize the look of the panel for myself. But of course the locations of the hardware must remain the same.
anybody???
delayed
https://electricmusicstore.com should have both panels and a drill sheet
Laughing
Has anyone here made the endeavor to drill out their own panel? I want to try when I get into a machine shop class later next month, but I'd love to hear some stories first.
bemerritt
Laughing wrote:
Has anyone here made the endeavor to drill out their own panel? I want to try when I get into a machine shop class later next month, but I'd love to hear some stories first.


I would find the drilling/milling easier than the printing part personally.
papz
To work with the iProgram card, pins 2 and 4 of both rows on the edge connector also need to be connected to 0V.
These 0V connections are not implemented on the PCB but can be added easily.

solidstatedisaster
trimix wrote:
Since I can't seem to find anyone offering panels for the 208 right now, I was wondering if anyone has drawing files (especially drilling centres) for the 208.
Formats can be .svg .ai .dxf ... anything editable.
I'm not looking to make a clone... I actually want to customize the look of the panel for myself. But of course the locations of the hardware must remain the same.
anybody???



I would totally be down for a blank panel and a frame for the reverb. I am unafraid of customizing stuff.
papz
More info about the iProgram card.

The clock connection is on rear pin 5 of the card edge connector and on pin 8 of the power connector.
The data connection is on rear pin 6 of the card edge connector and on pin 9 of the power connector.

I won't add the extra connections that the iProgram card needs to the final revision of the PCB, not many 208 clone users seem interested in the iProgram card and these contacts could be used for other purpose, it's easier and neater to add a connection than to cut a trace.
search64
I've been preparing for the next run of these boards by creating a BOM based on the 208r version.

Some collected questions based on my research:
- I've read Papz say somewhere to use 15mm standoffs, BOM says 17mm. Which to use?
- The replacement pn3565 has a different pinout than the 2n3563 from the original. Just want to make sure I know how to solder these in... Seems like when looking at the card from the component side, the flat side needs to point to the right, right? Anyone?
- The looping envelope looping board can be implemented in this as well? How do I wire this up without making another hole in the front panel. Which switch off position do I abuse for this?
- If I've read correctly, the C&K switches with solder lugs will fit this board, whereas the 208r requires the solder pin version?
- Can I use this cap instead of the 390uF Sprague one? https://nl.mouser.com/ProductDetail/Vishay-Sprague/TVA12087?qs=%2fha2p yFadujX3auk1NrQ%2fSwhQVMAV6PyngMw2mPnahLfacOT2MQazg%3d%3d
- Is there an alternative to the CA3046 needed for the pA726 that Mouser carries?
cygmu
search64 wrote:

- Is there an alternative to the CA3046 needed for the pA726 that Mouser carries?

I don't think so. You can get 3046s in various places without too much hassle but they are long obsolete in DIP form.

The SOIC version, LM3046, is also end-of-life but still available at Mouser and could be used with an adapter board.
search64
cygmu wrote:
search64 wrote:

- Is there an alternative to the CA3046 needed for the pA726 that Mouser carries?

I don't think so. You can get 3046s in various places without too much hassle but they are long obsolete in DIP form.

The SOIC version, LM3046, is also end-of-life but still available at Mouser and could be used with an adapter board.


Ok... sad banana

Is it just me, or is it strange to sub an obsolete part with a different obsolete part? Anyhoo... Thanks!
papz
I bought CA3046 from this ebay seller and they work fine.
https://www.befr.ebay.be/itm/5PCS-IC-INTERSIL-HARRIS-DIP-14-CA3046-CA3 046E/181950329911?hash=item2a5d15b437:g:dAYAAOSw8-tWYBDS
Working equivalents are listed in the pA726 build notes.

Use 15mm standoffs, as mentioned in the build notes.

PN3565 on card 6 should be mounted with the rounded side pointing to the outside

Any common 330µF electrolytic cap is ok on board 12.

Both PCB and panel mount switches can be used, as mentioned before.

The envelope looper circuit input should be connected to an orange banana and its output to the switch like on the pic (yellow cable to the mode select switch).

search64
Coolio. Thanks!
beautyofdecay_
As an experiment I used LEDs with a flat top on my 208. I rather like it!

papz
This looks nice.
search64
I see you also went with the BEMI no-nuts look hihi
delayed
beautyofdecay_ wrote:
As an experiment I used LEDs with a flat top on my 208. I rather like it!



What part number are they?
cygmu
Wow the flat LEDs look great. I absolutely do not want the hassle of lining them up properly but I gotta try...
Siri
Is this panel compatible 100%? https://electricmusicstore.com/products/208-rev-2-1-front-panel-frame- for-diy-kit
delayed
Per his other thread, yes the panels fit.
beautyofdecay_
search64 wrote:
I see you also went with the BEMI no-nuts look hihi

Heheh hihi Just used only a couple of nuts to fix the panel as long as I'm still building.

delayed wrote:
What part number are they?

These are from Mouser: 604-WP424IDT, but I think you can get them also from Thonk: http://www.thonk.co.uk/shop/new-style-flat-top-leds-turing-pulses-vact rol-mix/

cygmu wrote:
Wow the flat LEDs look great. I absolutely do not want the hassle of lining them up properly but I gotta try...

It's just 9 LEDs. It's not that hard. Definitely worth the effort I think!
papz
Thanks for the reference, these LEDs look nice and are not too bright (5 mcd), I'll definitely add some to my next Mouser order. thumbs up
papz
A small trace is missing between R28 and R30 on board 4 of the promo PCBs.

search64
Is that fixed on the final boards?

What sort of wire do you suggest to use for the build? For connecting bananas, the reverb, and the power?
beautyofdecay_
papz wrote:
A small trace is missing between R28 and R30 on board 4 of the promo PCBs.

Thanks! I fixed it on my card.
papz
It will be fixed on the final boards.

The reverb and preamp need shielded cable.

For the power, stranded AWG22.

For the bananas, same one or any thinner stranded cable is ok.

There's a dedicated topic https://www.muffwiggler.com/forum/viewtopic.php?t=129092&highlight=
search64
we're not worthy
solidstatedisaster
I missed the panel from EMS, so I decided to make my easel look like the prototype. Who knows, maybe I will make mine crazy custom looking, but this will get me going.
search64
Working through the BOM posted earlier in this thread, it's good to note that especially in the case of all the XICON resistors that it's actually cheaper to order 10 than 2-9. A single resistor is 14 cents, 10 are 19 cents. Since it's always good to have some extra, I'd say it's good to order at least 10 of each value.

I'm also seeing that Mouser states the LM301 is end of life, with no through hole alternative available. There's still plenty available now, but perhaps it's good to see if a more opamp would work in these positions?

Lastly, the BOM has no IC sockets.
bemerritt
Anyone find a suitable IC for the adaptor board that is available either on mouser or digikey?
papz
SMT 3046s are available from Mouser, these should work with a DIP/SMT adapter like 535-14-350000-11-RC
papz
The panels and reverb frames are back in stock.

If you bought the PCB set only you should receive an e-mail from me, in case the e-mail doesn't arrive, please contact me.

These are NOT available standalone to people who didn't buy the PCB set. It's not worth asking.
Bundles including PCB, panel and reverb frame will be available in March via my website.

Thanks
search64
Can't wait for the PCB sets! It's peanut butter jelly time!
cygmu
papz wrote:
The panels and reverb frames are back in stock.

These are NOT available standalone to people who didn't buy the PCB set. It's not worth asking.


Once the PCBs are available, if someone buys one set of PCBs, is it worth asking whether they might be able to buy two panels?
papz
Yes
beautyofdecay_
Is connecting pin 2 and 7 on the pa726 PCB only needed for card 6 or also for card 7?
papz
It's needed for both on the early pA726 (with square corners) but not on the latest revision (with roundish corners).
beautyofdecay_
Thanks!
I only saw the wire on one of the PCBs in the pictures on your site so I just wanted to be sure.
papz
Yes, sorry, I really should change these pics. (hides)
This was the very first batch and a trace was missing on the board 6 connector, hence the cable. For board 7, the 2-7 link was on the board itself.

I removed the pics and will try and do new ones this weekend.
bemerritt
papz wrote:
Yes, sorry, I really should change these pics. (hides)
This was the very first batch and a trace was missing on the board 6 connector, hence the cable. For board 7, the 2-7 link was on the board itself.

I removed the pics and will try and do new ones this weekend.


I can send you some pics once i build mine up this weekend if you want.
papz
Thanks for the kind offer, your pics will most likely be better than mines thumbs up
Which IC will you use btw ?
bemerritt
Ended up going with a US ebay seller (had good ratings) that had quick shipping. Cheaper than the adapter plus the alternative IC.

Excited to finally get the 'other' adaptations off my build and get some good tracking.
beautyofdecay_
papz wrote:
Yes, sorry, I really should change these pics. (hides)
This was the very first batch and a trace was missing on the board 6 connector, hence the cable. For board 7, the 2-7 link was on the board itself.

I removed the pics and will try and do new ones this weekend.

No problem, that's why I asked cool
I'm using the old version (square corners) of the PCB btw.

Here is a picture of my build. Feel free to use it on your website if it's useful.


papz
Thanks, nice pic.
Hope the headers won't make adjusting the motherboard trimpots too tricky.
beautyofdecay_
Added a picture of the back of the PCBs.
Yes, the trim pots are still reachable. I cut of the male headers on the cards a bit to shorten the distance.
papz
Did you also remove the plastic part from the male headers ?
Otherwise, the distance remains the same regardless of the pins length.

Could you also take a pic with the boards 6 and 7 mounted to the MB please ? Thanks we're not worthy
beautyofdecay_
No, I used extra long headers, that's why I needed to shorten them a bit to match them with the female headers on the pa726 PCBs.
Here a few pics from my build. Depending on the angle of the picture it looks like the trim pots are not accessible anymore. However, with a small screw driver all the trim pots can still be reached.


card 6


card 7


both cards
papz
Thanks !
search64
Silly question perhaps, but does anyone have the Mouser codes for the 90 degree pins and shunts (the jumpers), for the pA726's?
beautyofdecay_
I used these for the angled 2 pin headers: 855-M20-9750242.
I had plenty of jumpers in store so didn’t have to buy any. But you could use this: 474-PRT-09044. Or search for “2 pin jumper”.
the bad producer
All going well here - so far!

papz, could you (or anyone else) shed light on this:

2 x 470ohms and 2 x 10k resistors
for the noisy headphones output fix on the
motherboard


I can't find (yet) any reference to this!
search64
the bad producer wrote:
All going well here - so far!

papz, could you (or anyone else) shed light on this:

2 x 470ohms and 2 x 10k resistors
for the noisy headphones output fix on the
motherboard


I can't find (yet) any reference to this!


Download the images from his website of where all the values go. He photoshopped them in on the motherboard near the gap where the headphone jack goes:


On the right...
the bad producer
hihi d'oh!

I didn't look there thanks!
papz
Thanks thumbs up

It's not photoshopped, it's gimped. lol
search64
Fair enough.

Now get me some boards so I can start soldering already! hyper
papz
The order is sent, waiting for the manufacturer's holiday end in a few days.
Should be available in the first half of March.
Om
search64
Good thing Mouser is out of some items I need anyway...

Oh btw! Question: the BOM is for 2V/oct, right? Or 1.2v/oct?
papz
Yes it's for 2V/oct but a selection on test of the CV scaling resistors is needed for accurate calibration, regardless of the choosen voltage. It's good to have various resistors on hand anyway and not only rely on the BOM, other resistors may need selction on test too.

You can get the parts not available from Mouser from other suppliers.
Mouser is not the only one, neither the cheapest...
solidstatedisaster
I was wondering how far everyone is on their builds?

I am 2 components (from ebay) away from being complete with parts, and one panel away from wiring everything together.

I was also wondering what sort of modifications we should be expecting to make on these boards? It looks like Roman's versions had a lot of resistors that needed to be changed to get it to track correctly, and was wondering if we should expect the same?
papz
It's in the build notes.
http://www.portabellabz.be/images/208/208%20build%20notes.pdf
search64
papz wrote:
Yes it's for 2V/oct but a selection on test of the CV scaling resistors is needed for accurate calibration, regardless of the choosen voltage. It's good to have various resistors on hand anyway and not only rely on the BOM, other resistors may need selction on test too.

You can get the parts not available from Mouser from other suppliers.
Mouser is not the only one, neither the cheapest...


That's true, but ordering from lots of different suppliers also comes with more shipping costs.

Plus, I've had my project at Mouser ready to order for some time now, including banana cables and jumpers, and everything I need for the 218r rev1... 600 bucks all in all Dead Banana
papz
Indeed
In fact I never order the parts for a single project only, so I think from a different point of view.
solidstatedisaster
papz wrote:
It's in the build notes.
http://www.portabellabz.be/images/208/208%20build%20notes.pdf


I have read that, I guess Dave Brown's page made it seem like there were more changes. I am very excited to wrap this up and start making music!
papz
I built many 208s and the only changes I did regarding tracking are the ones described in my build notes.
This doesn't mean it's the only way to proceed, since there is no official calibration procedure. Dave Brown wrote "I personally would like a little more low frequency", why he did more changes.
Feel free to experiment and find the settings that you're happy with. That's a great aspect of DIY : you can customize your builds to your own needs. wink
jonny_w
Has anybody had any luck with UTsource for the rare parts?
papz
All the rare parts I bought from UTSource are ok, except fake µA726, but are not needed for this build thanks to the pA726.
tarandfeathers
jonny_w wrote:
Has anybody had any luck with UTsource for the rare parts?


As Papz says, mostly fine. I also found that none of the FETs I bought were within spec, let alone within the spec required for the sine shaper, but they were FETs of some description. For the critical stuff J201 or similar is just as good.
search64
I'm sure you all found this already, but I bought the very handy 208 hardware kit and rare parts (and a nice case) from Weedywhizz:
https://www.samodular.com/buchla-cases-and-parts/buchla-diy-parts/part s-kits-buchla-modules/

papz
PCBs are ordered, should be available around mid-March.
search64
It's peanut butter jelly time!
beautyofdecay_
It's alive! cool
Just a quick test after finishing the last two cards. Only thing missing at this moment is the reverb tank.
Everything seems to be working as it should. Now on to calibrating...

I do need a new case as the old one for my rev1 version is not deep enough.

Thanks Constantin for an easy build!

papz
Yeah ! thumbs up
Congrats and thanks for the useful details and comments.
search64
beautyofdecay_ wrote:
It's alive! cool
Just a quick test after finishing the last two cards. Only thing missing at this moment is the reverb tank.
Everything seems to be working as it should. Now on to calibrating...

I do need a new case as the old one for my rev1 version is not deep enough.

Thanks Constantin for an easy build!



That sounds reassuring applause

I found the reverb tank at tonefactory.nl btw...
beautyofdecay_
search64 wrote:
I found the reverb tank at tonefactory.nl btw...

Thanks for that link. Didn't know them.
I ordered mine from banzaimusic.com.
papz
Tanks are also available from TAD.
http://www.tubeampdoctor.com/en/shop_Reverb_Cans_Effects_Accutronics_R everb/Accutronics_Reverb_Can_1BC2E_4677

The wait with Banzai can be very long, they list a lot of items that they don't have in stock actually, regardless of what their website claims. I had so many bad experiences with them that I no longer buy anything there.
beautyofdecay_
Yeah, I know. I usually also look at alternatives as it normally takes a lot longer than stated on their website... confused
solidstatedisaster
Got my 208p working today. The Random output is not functioning correctly, but everything else seems to be working right. It is going to take a while to calibrate it, but I am very excited to get it tuned.

Here is my first doodle
https://www.instagram.com/p/BfpZYeUDP3G/
papz
I like the acrylic panel thumbs up

For the random out issues, try and swap the ICs on board 2 , starting with the 4016/4066 which are often in cause.
solidstatedisaster
Alright, got the Random fixed! In the interim, I developed two issues.

Issue 1) the square wave on the complex oscillator and the shape knob have stopped working, for the most part. Every once and a while it comes back on, and I get it, but then I twist the shape knob, and it goes back to a sine wave.

Issue 2) I developed a Sequence issue where it stopped triggering the fifth note, so I replaced a 4013, because it looked weird, and now it skips the third note, and randomly triggers the 5. If I get the pulser up fast enough, it will trigger 3 and 5 about every other pass.

On the plus side, I got both oscillators tuned to scale almost perfectly, with very little drift, and this thing is super fun to play with, even with my issues.
search64
For issue 2: have you tried adding decoupling caps to most of the ICs on the sequencer card? This seems like a common issue.

Was Papz tip the solution for the random?
cleaninglady
Great thread papz ! SlayerBadger! SlayerBadger! SlayerBadger!

Even though i did a 208r V2 build, there's still plenty of things here that are relevant and get me thinking. Especially, the Dual Vactrol on Card 10 and 11. I would have done that in the beginning if i knew i could have.

Thanks beautyofdecay_ and for pointing that out.

the bad producer, i'll be dropping by in May to see you and have a few pints. Consider me available as solder monkey of you're still on the project then.
beautyofdecay_
As everything seemed to work OK I finished up the front panel yesterday. Mounting all the switch nuts and front panel screws.

Than spent about an hour figuring out why the 208 didn't work anymore confused. All sequencer LEDs were all on, the other LEDs displaying strange behaviour and no sound.
Eventually figured out that the slot connector was creating some kind of short circuit. Once I removed it everything worked fine again.

Still have to figure out what I can do to fix this.
beautyofdecay_
solidstatedisaster wrote:
Issue 2) I developed a Sequence issue where it stopped triggering the fifth note, so I replaced a 4013, because it looked weird, and now it skips the third note, and randomly triggers the 5. If I get the pulser up fast enough, it will trigger 3 and 5 about every other pass.

Make sure the control switch is in "front panel" position. I experienced similar issues when this switch was in the "both" or "prog-board" position without anything connected to the interface slot...
search64
How did you guys match the Vbe of the transistors (2N3565 on card 6). Just a diode test?
beautyofdecay_
search64 wrote:
How did you guys match the Vbe of the transistors (2N3565 on card 6). Just a diode test?

I used the Ian Fritz test circuit as described in this thread: https://www.muffwiggler.com/forum/viewtopic.php?t=81990&start=all&post days=0&postorder=asc

BTW: I used PN3565 instead of 2N3565.
papz
Match these is not essential.

Maybe both your edge connectors are misaligned ?
solidstatedisaster
search64 wrote:
For issue 2: have you tried adding decoupling caps to most of the ICs on the sequencer card? This seems like a common issue.

Was Papz tip the solution for the random?


I haven't tried the decoupling caps, someone will have to break that down with further detail for me to try it.

I am sure Papz solution would have worked fine, but I had a blown 4015, it was obvious in the right light, so switching that fixed random.
solidstatedisaster
[/quote]
Make sure the control switch is in "front panel" position. I experienced similar issues when this switch was in the "both" or "prog-board" position without anything connected to the interface slot...[/quote]

That is good to know, I didn't try that.
papz
If the sequencer works fine, no coupling caps are needed.
Should be added if it for example skips a step erraticaly.
This seems related to the ICs used, mostly 4013.

I don't think Solidstatedistaster's issue 2 is related to this, rather another IC to swap.

For issue 1, I'd suspect a bad contact or solder joint.
beautyofdecay_
papz wrote:
Maybe both your edge connectors are misaligned ?

Well, the motherboard connector is a bit off but as it is flush with the PCB I cannot do a lot about that. When checking the front panel edge connector however, I noticed that a couple of contact strips on both sides of the connector were warped and touching each other. After I bend them back so they did not touch one another I reinstalled the front panel connector and now the 208 keeps functioning without problems cool
papz
thumbs up

To match transistors, I use a cheap Chinese transistor tester, various types are available on ebay for about €20.
Maybe not the most accurate, but enough for matching purpose.
captnapalm
sanemalkavian wrote:
Hi everyone. I am new at this, so not sure how good it is.

I compiled a Mouser project based on the BOM lists from PDFs. Mouser project has all the components that can be found based on those BOMs, so parts that are rare and cannot be found on mouser, including sliders, pots and hardware parts are not included.

I also included everything needed for pA726 except for CA3046 and two pin header.

In the attachment are all Excel files generated from PDFs, including a compiled mouser cart, where all parts that are not in stock are replaced with other part number. Compiled Excel doesn't include parts needed for pA726.

I hope this will help.

Mouser project 208


Hi sanemalkavian, thanks for providing the cart!
However it looks like there are some components that don't belong on a 208. Perhaps you also ordered 218 parts at the same time? I see an ST/Link programmer and other items...
search64
captnapalm wrote:
sanemalkavian wrote:
Hi everyone. I am new at this, so not sure how good it is.

I compiled a Mouser project based on the BOM lists from PDFs. Mouser project has all the components that can be found based on those BOMs, so parts that are rare and cannot be found on mouser, including sliders, pots and hardware parts are not included.

I also included everything needed for pA726 except for CA3046 and two pin header.

In the attachment are all Excel files generated from PDFs, including a compiled mouser cart, where all parts that are not in stock are replaced with other part number. Compiled Excel doesn't include parts needed for pA726.

I hope this will help.

Mouser project 208


Hi sanemalkavian, thanks for providing the cart!
However it looks like there are some components that don't belong on a 208. Perhaps you also ordered 218 parts at the same time? I see an ST/Link programmer and other items...


...this is very strange... I copied his cart as a personal project in my own account and adjusted it for myself. This is my cart eek! hmmm.....
search64
Digging a bit deeper. It's not exactly my cart... Some things are off. This is really strange. Anyway, I'll try to fix it today.
search64
Ok I fixed it now, so no more 218r elements in there. I did leave the IC sockets in there, which were missing in the initial cart. I also put 10 for every resistor as a minimum, as the price of the Xicon's drops off if you buy 10 or more. Lastly, the cart includes the C&K toggle switches required, so no need to buy those off of Digikey.

DISCLAIMER: please double check the BOM before ordering this cart! I take no responsibility for anything missing. As far as I'm concerned this is just a starting point.


Oh, there is no power connector for the cable in this cart. So should you need one, add one of these EDAC connectors (587-306-50-010). You can solder a small piece of wire across the fourth pin connector to ensure you don't accidentally plug it in backwards (stole that idea from Weedywhizz).
captnapalm
search64 wrote:
Ok I fixed it now, so no more 218r elements in there. I did leave the IC sockets in there, which were missing in the initial cart. I also put 10 for every resistor as a minimum, as the price of the Xicon's drops off if you buy 10 or more. Lastly, the cart includes the C&K toggle switches required, so no need to buy those off of Digikey.

DISCLAIMER: please double check the BOM before ordering this cart! I take no responsibility for anything missing. As far as I'm concerned this is just a starting point.


Oh, there is no power connector for the cable in this cart. So should you need one, add one of these EDAC connectors (587-306-50-010). You can solder a small piece of wire across the fourth pin connector to ensure you don't accidentally plug it in backwards (stole that idea from Weedywhizz).


Great, thanks. It should also be noted that there are a variety of banana cables and shorting bars in this BOM that some might not need.
search64
captnapalm wrote:
search64 wrote:
Ok I fixed it now, so no more 218r elements in there. I did leave the IC sockets in there, which were missing in the initial cart. I also put 10 for every resistor as a minimum, as the price of the Xicon's drops off if you buy 10 or more. Lastly, the cart includes the C&K toggle switches required, so no need to buy those off of Digikey.

DISCLAIMER: please double check the BOM before ordering this cart! I take no responsibility for anything missing. As far as I'm concerned this is just a starting point.


Oh, there is no power connector for the cable in this cart. So should you need one, add one of these EDAC connectors (587-306-50-010). You can solder a small piece of wire across the fourth pin connector to ensure you don't accidentally plug it in backwards (stole that idea from Weedywhizz).


Great, thanks. It should also be noted that there are a variety of banana cables and shorting bars in this BOM that some might not need.


Actually, there shouldn't be anymore. Pretty sure I removed those. There are only bananas jacks now.
captnapalm
search64 wrote:

Actually, there shouldn't be anymore. Pretty sure I removed those. There are only bananas jacks now.


Ah yes you're right, sorry. I was looking at a cached version. Carry on...
papz
Thanks for the corrections thumbs up
pathein
am soldering the motherboard at the moment and having some questions on the LEDs

For the sequencer led 1 to 5, i supposed the current limiting resistors are the 220R ones.

How bout for led 6, 7, 8 and 9?

If i have to change the resistors value to cater for other colours but brighter ones, will it affect other functions?
search64
pathein wrote:
am soldering the motherboard at the moment and having some questions on the LEDs

For the sequencer led 1 to 5, i supposed the current limiting resistors are the 220R ones.

How bout for led 6, 7, 8 and 9?

If i have to change the resistors value to cater for other colours but brighter ones, will it affect other functions?


For the two LPGs, the resistor is on the LPG cards (look for the 220r resistor). Haven't checked, but suspect the same goes for pulser and EG.
pathein
thanks search!

That made sense, will check out the cards schematic for the resistors.
papz
220 ohms R45 on card 10 and R36 on card 11 are not in series with the LED but with the LPG output.

To add a resistor in series with the LED of the pulser and envelope, I cut the trace on the board 3 and 4 between the Molex connector and 2N1711 (LED driver) and bridge with a resistor.
https://www.muffwiggler.com/forum/viewtopic.php?p=2725583&highlight=#2 725583

The same can be done on the motherboard for the LPGs, cut a trace going to a LED's leg and bridge with a resistor.

Resistor should be selected on test to match the LED type and desired brightness.
search64
Hmm, didn't follow the traces well enough it seems. So those leds have no resistor to limit current?
pathein
going through the info papz posted on the softer leds. I found some leftover leds for other projects, same family from lumex and lesser intensity at 6 mcd.

The product code is SSL-LX3044HD. Seem like mouser dont have it, but can be found via digikey or element14.

i will probably try out the leds and stock resistor values to see how it will be.
solidstatedisaster
I never fully figured out where the bad solder joint is on my complex oscillator, but I have got it to where I can press on my acrylic panel, and it fixes the bug.

A buddy of mine brought over his Octotrack last night, and we sampled and jammed for a few hours, and made a 80's film soundtrack. I love this synth, thank you Paps for doing this.

Now I need to figure out how to wire midi to my 218e
pathein
quick question, is the 56 pin edge connector same as theLW-N28A2G Connector?
search64
pathein wrote:
quick question, is the 56 pin edge connector same as theLW-N28A2G Connector?


Almost, but not entirely:
https://www.samodular.com/buchla-cases-and-parts/buchla-diy-parts/part s-kits-buchla-modules/

One has pins, the other solder lugs. I’m not sure if that’s a problem...
pathein
ahh ok, that should be fine then.

i have both but using the lw connector on the panel and the 56 pin connector on the motherboard pcb as i didnt want to cut off the protruding part on the 56 pins ones to fit the panel
papz
If a connector like the one on the SAmodular pic is used, I recommend to cut off the protruding part anyway to avoid a gap. Easy to do with a hot blade or good cutting pliers.
Mount this one to the PCB and a LW-N28A2G to the panel may need to reduce the transfer card.
solidstatedisaster
Alright, I somehow managed to mess up something on my complex oscillator while changing my acrylic panel to my beautiful new 208p panel. The Mod osc still is fine, but the complex is very quiet, here is a vid of it https://www.dropbox.com/s/ffup38dbka2w376/video-1521205704.mp4?dl=0 . I still cant track down the issue on my Complex oscillator wave shape. If anyone can help me track these issues down, I would appreciate it. I suspect a bad solder joint, but I am at that point of frustration trying to find it.

Thanks![/url][/video]
papz
The loudness problem may also be in LPG1 (card 10).
Did you try and replace the waveshape pot and switch ?
solidstatedisaster
papz wrote:
The loudness problem may also be in LPG1 (card 10).
Did you try and replace the waveshape pot and switch ?


I tested the pot with a multimeter and it seemed fine. I reflowed the switch, the entire card pins for 8 and 9, all the resistors around the switch and pot, and it still seems to be an issue. The loudness this is really weird, I added new shielded cable for the envelope follower, to cut down on the noise, and that was the only thing I changed on that card.
papz
Then I would suspect the waveshape pot or switch.
If are faulty, reflow won't help.
You can test the switch with a continuity test.

I'm afraid you maybe also changed something else on card 10 although it was not intentional. Mr. Green
Double check it.
solidstatedisaster
papz wrote:
Then I would suspect the waveshape pot or switch.
If are faulty, reflow won't help.
You can test the switch with a continuity test.

I'm afraid you maybe also changed something else on card 10 although it was not intentional. Mr. Green
Double check it.


I dont have any extra switches lying around, but that has always worked perfectly when it was working. I have a ton of 10k pots, I can give one of those a shot and see what happens.

I got a lot of digging ahead of me tonight smile
solidstatedisaster
Okay, it is not the pot that is the issue of the wave selection, nor is it the switch, so I am sort of at a loss on that. I have replaced all the chips on card 8 and 9.

It wasn't a bizarre short from the new shielded cable I used, because i removed it. The gates were working perfectly before I took the panel off. What could be wrong?
papz
Most PCBs arrived today, the parcel with the motherboards was delayed and will arrive tomorrow.
So I'd be able to start shipping on Wednesday.

Various options are available, including mini distro board or ToolBox and BOB expander.

http://www.portabellabz.be/208pcb.html
search64
papz wrote:
Most PCBs arrived today, the parcel with the motherboards was delayed and will arrive tomorrow.
So I'd be able to start shipping on Wednesday.

Various options are available, including mini distro board or ToolBox and BOB expander.

http://www.portabellabz.be/208pcb.html


It says it’s sold out...
papz
Can you try again please ?
Paypal sucks and the code is sometimes modified when I save the page very frustrating
You can rather use bank transfer if in the EU, it's cheaper, just pm or e-mail me for the bank details.
search64
PM’d!
papz
Paypal issue seems fixed, several people already purchased.
It's peanut butter jelly time!
solidstatedisaster
papz wrote:
Then I would suspect the waveshape pot or switch.
If are faulty, reflow won't help.
You can test the switch with a continuity test.

I'm afraid you maybe also changed something else on card 10 although it was not intentional. Mr. Green
Double check it.


Finally figured out both of my issues! The wave selection problem was the program selector switch, and the volume issue was a slider... it works beautifully now. Thanks for the ideas on fixing it, and thanks for the killer synth.
papz
thumbs up
Is the "program selector switch" the "control" one ?
Can you please explain how it affected the CO wave ?
Chaotic
I'm in It's peanut butter jelly time! nanners
solidstatedisaster
papz wrote:
thumbs up
Is the "program selector switch" the "control" one ?
Can you please explain how it affected the CO wave ?


As far as I can tell, it was one leg of the switch that activates the program card wasn't properly soldered, and it caused the CO waveform knob to not work, and the only way to activate it was to press on the pot until it flexed into connection. While I was changing the panel, and had the lp1 issue, I did a shitty job touching up the program switch, never solder hungry, and caused a bridge that made the whole 208 only function in Both mode. Once I fixed that, I got normal function back. The lp1 fader issue was a bad connection, and being hangry worked in my benefit, because I stopped treating my synth as a precious instrument, and just started flicking it back and forth until it worked. Resoldered, and my problem was fixed.
captnapalm
I found a missing trace on card 12 tonight (these are the promo PCBs). It connects the reverb tank via card edge pin 6 to the input (pin5) of IC1. Not sure if this is fixed in the production boards? You can see the trace there on one of Roman's card 12s.

Sorry for my fluxy pic; haven't cleaned them yet.

captnapalm
captnapalm wrote:
I found a missing trace on card 12 tonight (these are the promo PCBs). It connects the reverb tank via card edge pin 6 to the input (pin5) of IC1. Not sure if this is fixed in the production boards? You can see the trace there on one of Roman's card 12s.


I just re-read the build notes and I see now this is by design assuming you’ll be connecting the tank directly to card 12 rather than going through the motherboard. I’m testing each of my cards on a 208r2 so the reverb wasn’t working and had me scratching my head for a while. Carry on!
papz
Hi Luther

Sorry for the head scratching, it's always good to double check the build notes. wink

Yes, I intentionaly removed this trace because it's much better to connect the reverb with a shielded cable rather than via the board to avoid bleed issues.
So builders don't have to cut the trace.
Btw, I'm not a fan of the cap + resistor mod visible on your board, the shielded cable works better to fix the bleed.

The final boards currently available have dedicated pads to ease the shielded wiring.


This mod was done in some original 208s as well, according to Dave Brown's page.
solidstatedisaster
Alright, I spoke too soon. I had 2 days of a perfect working 208, recorded a few YouTube videos, I was having a blast. I turned it on last night, and the complex oscillator was super quiet again, with the same ground hum. I changed out the slider, that didn't change anything. I still am not convinced that I have a bad part in the chain, as that would have no output, but finding it is driving me crazy. I emailed Dave Brown about it, and this was his response:

"Technically, the audio path is card 9 to card 8 to card 5 to card 10.

 

On card 8, the VCO1 outputs are square on edge pin 14 and triangle on pin 15.  The triangle from card 9 comes in on pin 9.  They all get waveformed and come out on edge pin 4 so verify all those pins.

 

Pin 4 goes over to card 5 pin 8.  I have a block diagram on my site for card 5.  It goes through IC2 to select the proper path   Note the preamp goes through this same path, so if you select balanced external and it doesn’t work, then the issue is past this point.  From IC2 it goes through IC4 with output on pin 12.  It goes through the modulator and comes out on IC5 pin 10.  You can’t look at it on the edge pins.  From there it goes to card 10 where it is present on IC2 pin 3.   It goes through the vactrols and comes out on edge pin 8.  From there is goes to the channel A pot on the motherboard and then to card 12 IC1 and is output on pin 3.  That goes back to the motherboard for the master, etc.

 

See if you can follow it along."

I won't have time to try this until tomorrow, if anyone has any other ideas, I am all ears.
solidstatedisaster
Update on the continuing saga. I followed Dave's recommendation, and (for now) my complex oscillator is at normal volume, with normal functions. I wish I knew what I did to fix it, but I reflowed so many connections, I could have been anything.

The wave selection was the stupidest thing, and I am super embarrassed to admit it, but if it helps the herd, it is worth it. After all this soldering, desoldering, resoldering, following the traces, I finally found the issue. It was a short on the motherboard at the "from program" banana jack. I literally couldn't see it, seriously, not even under a magnifying glass. I resoldered the wire, and the short is gone. I think in the future, I am going to use bus wire for the banana jacks...

Good luck fellow builders.
trimix
Heywhat are the specs for the 208 reverb tank? Size, impedence, etc.
The BOM only lists "Spring reverb tank - Belton"
captnapalm
trimix wrote:
Heywhat are the specs for the 208 reverb tank? Size, impedence, etc.
The BOM only lists "Spring reverb tank - Belton"


Belton model 1BC2E

User xpander has some in stock and is easy to work with.
Or you can purchase direct from Belton in Korea.
http://www.accutronicsreverb.com/main/?skin=sub01_01.html
papz
I added the reverb reference to the buildnotes.
Thanks
search64
That's good, but it most definitely IS in the BOM from electricmusicstore. Just have a look at the left most column:

https://cdn.shopify.com/s/files/1/0388/9729/files/208-BOM-v2.1-MB.pdf? 9331062364855035085
papz
Indeed.

In several builds (by me and other builders) a 4066 doesn't work for card 8 IC2 and a 4016 is needed although 4066 is fine everywhere else but right now I have in front a me a perfectly working 208 with a 4066 at this place. hmmm.....
I also updated the buildnotes about this.
heapish
cygmu wrote:
Wow the flat LEDs look great. I absolutely do not want the hassle of lining them up properly but I gotta try...


Masking tape on the panel. Solder one leg of each. Take off masking tape. Check. Adjust with tweeser/iron if needed. Solder other leg.
papz
New calibration infos and tips added in the build notes http://www.portabellabz.be/images/208/208%20build%20notes_final.pdf
search64
Cool. So to be sure: the original BOM is for 2V/oct right?
papz
I think so but I didn't calibrate a 208 for 2V/oct so far.

In the 70s with the original 218 design, small CV drifts could happen, 2V/oct helped compensate for the effect of a voltage difference : this was less on 2V/oct than on 1V or 1.2V/oct.
The current 218r and 218e designs output very accurate CV and 2V/oct is no longer needed.
solidstatedisaster
My preamp/envelope follower is super quiet, and I can't get it to output cv, is that normal for these models?
beautyofdecay_
Finally started calibrating my 208p and I started with the 2 pa726 modules.
When calibrating the pa726 boards I get an initial room temp voltage of 679 mV (on average, the reading fluctuates up and down a bit). Both modules are installed in the 208 when calibrating, this is correct?

After installing the jumpers and letting the modules warm up for half an hour, I can *just* get the pa726 on card 6 to 619mV (at the end of the trimmer range) but the one on card 7 I can only adjust to 613mV. Is that a problem?
I would expect the adjustment range to be larger. Maybe there is something wrong...?
papz
Preamp / env. detector : you should have CV at the banana output and audio signal in LPG2 when the routing switch is in its upper position.
Is your tinijax socket properly wired ?

pA726 : if you can go down up to 613mV, you should be able to get 619mV.
The trimpot setting can sometimes be extreme, depending on the IC used and the actual room t°.
The initial room t° voltage should be measured without jumper on the 208 module unpowered for at least 20 minutes, immediately after turned on and very quickly. If you have time to notice fluctuations it's already powered for too long for a good measurement.
beautyofdecay_
papz wrote:
pA726 : if you can go down up to 613mV, you should be able to get 619mV.
The trimpot setting can sometimes be extreme, depending on the IC used and the actual room t°.
The initial room t° voltage should be measured without jumper on the 208 module unpowered for at least 20 minutes, immediately after turned on and very quickly. If you have time to notice fluctuations it's already powered for too long for a good measurement.

I tried again just now after adding test pins to the pa726 boards so I could clamp my test leads to the PCB in stead of holding them myself...
The room temp voltage of both boards (without jumper) was as expected: 0.6936V and 0.6953V (stable, no fluctuations).
After installing the jumpers and switching on the 208 for half an hour I could adjust T0 as follows:
pa726 card 6: 0.5415-0.6252V (should be 0.6336V)
pa726 card 7: 0.5348-0.6195V (should be 0.6353V)

The max voltage is at the end of the range (fully counter clockwise).
Is that close enough or should I start replacing components?
papz
If your oscillators pitch remains tolerably stable, it is close enough.

Which CA3046 are you using ? I use these and have enough range for a comfortable adjustment : https://www.befr.ebay.be/itm/5PCS-IC-INTERSIL-HARRIS-DIP-14-CA3046-CA3 046E/181950329911?hash=item2a5d15b437:g:dAYAAOSw8-tWYBDS

In a previous build I used UL1111 instead of CA3046 and had to change a resistor value because the trimpot was off-range, was the 51k or 3k.
beautyofdecay_
I used the one in my pictures of the pa726 modules.
I then tried a similar version to the one you reference. Mine looks the same but has the following text to the right of the white vertical bar
CA3046
RCA H 410

However, the results are the same as with the previous versions... hmmm.....

I double-checked the components and all resistors are the right value. I will experiment with the 51k and/or 3k resistor to see if that helps.
papz
Weird...

But in fact, these 3046s don't look like on the ebay pic... They work fine however.

beautyofdecay_
I tried changing the 3k resistor to 2k3 (10k parallel to 3k) but that resulted in an even smaller adjustment range.
I then changed the 51k resistor to 46k7 (560k parallel to 51k) and I could adjust for the 60mV difference. The adjustment range is now 0.5844-0.6742V.
This is perfect to calibrate for the 0.6345V I need as T0 room was 0.6945V.

So I will now replace the 51k resistor with a 47k resistor on both modules and report back with the final results wink

UPDATE: With the 47k resistors installed, both pa726 modules are now calibrated to the right voltage!
n82558
Hello, I'm about to start work on my 208p and I found the mouser BOM on Page 1 of this thread, but is there a list somewhere of all the components that are NOT included on this BOM? Thanks!
captnapalm
n82558 wrote:
Hello, I'm about to start work on my 208p and I found the mouser BOM on Page 1 of this thread, but is there a list somewhere of all the components that are NOT included on this BOM? Thanks!


This should be everything not in the Mouser bom except for the boards/panel/reverb frame and general stuff like hookup wire etc. You'll also need the two ICs for Papz's ua726 boards.
search64
captnapalm wrote:
n82558 wrote:
Hello, I'm about to start work on my 208p and I found the mouser BOM on Page 1 of this thread, but is there a list somewhere of all the components that are NOT included on this BOM? Thanks!


This should be everything not in the Mouser bom except for the boards/panel/reverb frame and general stuff like hookup wire etc. You'll also need the two ICs for Papz's ua726 boards.


No this is no longer the case. Somehow I fucked up then fixed this BOM (search this thread). For one, the BOM now includes all switches and I believe it has IC sockets. Other than that, I think you should verify yourself, even though that’s a shitload of work.
captnapalm
search64 wrote:
captnapalm wrote:
n82558 wrote:
Hello, I'm about to start work on my 208p and I found the mouser BOM on Page 1 of this thread, but is there a list somewhere of all the components that are NOT included on this BOM? Thanks!


This should be everything not in the Mouser bom except for the boards/panel/reverb frame and general stuff like hookup wire etc. You'll also need the two ICs for Papz's ua726 boards.


No this is no longer the case. Somehow I fucked up then fixed this BOM (search this thread). For one, the BOM now includes all switches and I believe it has IC sockets. Other than that, I think you should verify yourself, even though that’s a shitload of work.


I ordered the BOM after you did the fixes to it, and it did contain everything it should have. There were a few extra caps and resistors that didn't match the BOM, but nothing was missing.
n82558
Even though its listed in the non-mouser BOM, I see that mouser carries part 2N4340 and 2N4339. Is there any reason not to order them there?
search64
n82558 wrote:
Even though its listed in the non-mouser BOM, I see that mouser carries part 2N4340 and 2N4339. Is there any reason not to order them there?


I believe I added it to the Mouser bom already...
search64


This is going to take a little while.
papz
It's easier to first populate the least high components, resistors and diodes. wink
search64
papz wrote:
It's easier to first populate the least high components, resistors and diodes. wink


This is personal preference.
papz
Indeed, personally I prefer the easiest way. lol
search64
Well I'm not going to argue with a pro Guinness ftw!


What order would you do the motherboard? Start with the pin headers?
papz
I populate the motherboard in this order
1. resistors, ceramic cap and diode
2. tantalum caps
3. pin headers
4. edge connector and trimpots
5. pots, slightly solder the central leg only to ease panel placement and alignment without bending legs, final soldering done after panel is mounted and pots nut screwed. It's good to add a second nut behind the panel to the 16mm ones.
6. sliders
7. switches
8. electrolytic caps and reverb frame
search64
thumbs up
needspeed
papz wrote:
I populate the motherboard in this order
1. resistors, ceramic cap and diode
2. tantalum caps
3. pin headers
4. edge connector and trimpots
5. pots, slightly solder the central leg only to ease panel placement and alignment without bending legs, final soldering done after panel is mounted and pots nut screwed. It's good to add a second nut behind the panel to the 16mm ones.
6. sliders
7. switches
8. electrolytic caps and reverb frame


Exactly!!!!!!!!!!!!!!!!!!!!!
search64
Any notes on mounting the panel? It seems as though it's impossible for the 9mm pots to be screwed to the panel, right?
captnapalm
search64 wrote:
Any notes on mounting the panel? It seems as though it's impossible for the 9mm pots to be screwed to the panel, right?


Correct, they just protrude through the panel holes enough for the knobs to be attached.

My panel attaching process is:

1. leave the cards and reverb tank off the motherboard to give access.
2. only solder one lead of the 16mm pots so they can be adjusted later.
3. mount all the banana jacks to the panel.
4. mount the program card to the panel.
5. attach the standoffs to the motherboard.
6. if the LEDs haven't been installed yet, put them through the holes now but don't solder.
7. screw one nut onto each of the switches, a little more than halfway down.
8. screw one nut onto each of the 16mm pots, all the way down.
9. set all switches to the center position. for 2-position switches, set them in-between.
10. lower the panel down over the switches and set it in place around them. you may need to fiddle with the 16mm pots a bit to let them through.
11. once in place, screw in the countersunk mounting screws.
12. put the switch nuts on loosely.
13. with a small long screwdriver, spin the nuts on the back side of the switches until they're flush with the bottom of the panel.
14. tighten the switch nuts on top of the panel snugly (don't over-tighten).
15. push the LEDs into place and solder from the back side.
16. heat the 16mm pot solder joints one by one and get them into place. put on the washers and nuts and snug them down.
17. mount the tini and headphone jacks from the sides.
18. solder the wires to connect all the banana jacks and the audio jacks.
19. solder the remaining 16mm pot leads.

I hope I remembered everything; I just put one together yesterday!
search64
Wow thanks! Good to know for sure I’m doing it right.
pathein
Was going through card 3 for the promo pcb and realised that C6 position on the pcb is different from the component overlay picture in the zip file from the first post. Am wondering if its correct to solder c6 as below?



papz
Yes

pathein
great, thanks papz!
Synesthesia
search64 hello hello !

I noticed you have 3 IC sockets on card 12.

It is normally advised not to used IC sockets for the LM380. they warm up - and use the ground plate as heatshield.
papz
A heatsink can be mounted to the LM380s.
search64
Good catch, but indeed I am using heatsinks. Like in the original I might add:

https://modularsynthesis.com/buchla/208/buchla_208.htm
search64
Going faster than expected...



Motherboard and 4 cards done (need to wire the bottom bananas still). Probably going to replace the headphone jack, not crazy about the plastic threading. Correct part number is 112BX instead of the N112BX as stated in the BOM.

How crucial is it to select the modulator vactrols? hmmm.....
papz
AM linearity depends on the modulator vactrols selection.
It works with unselected ones but a perfect calibration might not be possible unless you're lucky, the modulation waveform might be twisted resulting in a modulation frequency double of the MO's initial one at some point of the slider course.
search64
Is there another way of selecting them other than trying them one by one on the actual board? Is it a case of properly matching them, or is it some kind of unknown magic juju?
papz
I don't know, I select them on the actual board.
search64
What are people's experiences with the change suggested here (https://modularsynthesis.com/roman/buchla208v2/208spss.htm) to change C4 on card 11 to 47uF? I have a spare 47uF tantalum but just curious about any potential downsides.
trimix
Ok dumb question time...
Where are you guys getting these pA726 cards? I don't have anything in the pcb kit I received. And we need 2 of them, correct?
hmmm.....

edit: d'oh! as usual... search for hours, ask the question, then find the answer yourself in 5 minutes....
nevermind! Problem solved!
trimix
Just making my parts orders, and all the Vactrols listed in the BOM are VTL5C3...and to use a couple VTL5C3/2.

Right now I have enough VTL5C1 on hand to avoid getting any more. Can these be substituted for the 5C3's? Obviously if it can be done without blowing anything up, I can save a few bucks... FUUUCCKKKK!!!
search64
trimix wrote:
Just making my parts orders, and all the Vactrols listed in the BOM are VTL5C3...and to use a couple VTL5C3/2.

Right now I have enough VTL5C1 on hand to avoid getting any more. Can these be substituted for the 5C3's? Obviously if it can be done without blowing anything up, I can save a few bucks... FUUUCCKKKK!!!


I'm building mine using VTL5C1's except for the LPGs where I used dual VTL5C3/2.
cygmu
Maybe this post is useful when deciding on vactrols:
https://www.muffwiggler.com/forum/viewtopic.php?p=2437146#2437146
papz
A good selection on test of a vactrol is the most important. These parts may have a large tolerance even in a same batch of the same manufacturer.
Dave Brown compared accurately different vactrols that he has in stock : https://modularsynthesis.com/vactrols/vactrols.htm
No risk to fry anything using other type however.

@trimix : order well received thanks, I'll ship today. The pA726s come with the 208p PCB set, maybe did you buy a 208r ? I don't seem to have a record of a 208p purchase by you, but if you did and I forgot these in the set, please pm me and I'll refund you the pA726 purchase.
search64
search64 wrote:
What are people's experiences with the change suggested here (https://modularsynthesis.com/roman/buchla208v2/208spss.htm) to change C4 on card 11 to 47uF? I have a spare 47uF tantalum but just curious about any potential downsides.


Any ideas on this?
papz
No
captnapalm
search64 wrote:
search64 wrote:
What are people's experiences with the change suggested here (https://modularsynthesis.com/roman/buchla208v2/208spss.htm) to change C4 on card 11 to 47uF? I have a spare 47uF tantalum but just curious about any potential downsides.


Any ideas on this?


I changed it on my builds and didn't notice any difference either way.
search64
thumbs up
trimix
and did it work, or should I spring for MORE vactrols? I agree with using the VTL5C3/2 's
trimix
search64 wrote:
trimix wrote:
Just making my parts orders, and all the Vactrols listed in the BOM are VTL5C3...and to use a couple VTL5C3/2.

Right now I have enough VTL5C1 on hand to avoid getting any more. Can these be substituted for the 5C3's? Obviously if it can be done without blowing anything up, I can save a few bucks... FUUUCCKKKK!!!


I'm building mine using VTL5C1's except for the LPGs where I used dual VTL5C3/2.


oops lost the quote...
Again: did it work ok with the VTL5C1?
search64
Well... I still need to wire all the bananas, and the preamp input. And then test and adjust. So I don’t know yet Mr. Green

I’ll keep you posted!
search64
Couple of questions for the experts:

1. Looking at the motherboard, what is the point of the two test points, tp1 and tp2? What do you test there?
2. In the original Easel, what does this green wire do, and why is it left off in current builds?

papz
You're asking too many questions lol
search64
It’s a delaying tactic so I don’t have to plug it in test it (and potentially blow something).
papz
No worries, if something blows, it can be repaired. wink
search64
I fired it up and it's working smile ...mostly...

Timbre does absolutely nothing. I did alter R3 and R9 on board 7, perhaps that was too much?
papz
If timbre does absolutely nothing, the resistors value is probably not in cause.
I'd rather suspect faulty IC1 4136 or VT1 vactrol or bad solder or bent IC leg in the socket...

Just in case, the timbre affects sine and triangle only, if the CO outputs a square wave at full level, timbre won't affect it.
search64
Cool, will be troubleshooting tonight/tomorrow.

I think the timbre is the only thing not working at all, the rest is fine besides needing trimming. One small thing I need to think about is that the led's from the pulser and the envelope still bleed through, even though I did the 10k mod as suggested.

I'm already in love with the immediacy of the thing. It's so easy to play!
[s]https://soundcloud.com/jorgen-van-de-burgt/buchla-easel-snippet[/s]

(Btw, I quickly recorded that with Whatsapp on my phone from a headphone so sound quality sucks).
astroschnautzer
search64 wrote:
Cool, will be troubleshooting tonight/tomorrow.

I think the timbre is the only thing not working at all, the rest is fine besides needing trimming. One small thing I need to think about is that the led's from the pulser and the envelope still bleed through, even though I did the 10k mod as suggested.

I'm already in love with the immediacy of the thing. It's so easy to play!
[s]https://soundcloud.com/jorgen-van-de-burgt/buchla-easel-snippet[/s]

(Btw, I quickly recorded that with Whatsapp on my phone from a headphone so sound quality sucks).
If you have the possibility to use a linear psu it will take care of most of the bleeding...
search64
Can't. I'm using a Cincon 50W brick with the 211 in the case I bought from Samodular.
papz
The value of the resistor added in series with the LED depends on the LED type. Try and test with other values and find the best compromise between brightness and bleeding.
The LPG LEDs also cause some bleeding and a resistor can be added there as well.

Both the Cincon and 211 are not linear but switch-mode.
I didn't try with a linear PSU but I can keep the bleeding in the 208s I build to a very acceptable level with the Meanwell PD-2515 and 7805 + 7812.
LEDs bleed too in some instruments with a linear PSU, so I'm not sure the PSU is the cause.

My only experience with Cincon 12V block + 211 is in an Easel that I just built for someone who supplied with a suitcase powered this way. There were noises and interferences in the LPG1 output, especially noticeable with the MO in high frequencies.
Since the 211 was built by someone whose tech skills I know are not the most reliable and I have no experience with this board, I didn't attempt to track down the issue and prefered to immediately replace the whole PSU with a PD-2515 + my mini distro board which I know are ok.
The LPG1 is now perfectly quiet.
The LED bleeding is barely noticeable, only in high frequencies and when both the LPG and envelope or pulser LEDs lit together.
astroschnautzer
papz wrote:
The value of the resistor added in series with the LED depends on the LED type. Try and test with other values and find the best compromise between brightness and bleeding.
The LPG LEDs also cause some bleeding and a resistor can be added there as well.

Both the Cincon and 211 are not linear but switch-mode.
I didn't try with a linear PSU but I can keep the bleeding in the 208s I build to a very acceptable level with the Meanwell PD-2515 and 7805 + 7812.
LEDs bleed too in some instruments with a linear PSU, so I'm not sure the PSU is the cause.

My only experience with Cincon 12V block + 211 is in an Easel that I just built for someone who supplied with a suitcase powered this way. There were noises and interferences in the LPG1 output, especially noticeable with the MO in high frequencies.
Since the 211 was built by someone whose tech skills I know are not the most reliable and I have no experience with this board, I didn't attempt to track down the issue and prefered to immediately replace the whole PSU with a PD-2515 + my mini distro board which I know are ok.
The LPG1 is now perfectly quiet.
The LED bleeding is barely noticeable, only in high frequencies and when both the LPG and envelope or pulser LEDs lit together.
personally I didn't have as good results with a Meanwell PD-2515 and 7805 + 7812 than with a samodular psu, but best was a linear psu.
search64
Right, so obviously Timbre wouldn't work without C2 on card 7 installed very frustrating

Working now, but a bit bonkers, so adapting the resistor(s) to get a bit more control hihi
papz
thumbs up
Most circuits work better with all the needed parts installed indeed. lol
search64
WTH, this morning I had everything working. Now I screwed everything into the case, the reverb doesn't do anything anymore... turning the knob attenuates the signal before cutting it entirely. sad banana
papz
Broken or disconnected reverk tank.
search64
I can feel the spring vibrate, so the problem seems to be after the spring tank...
papz
The problem occured when you installed the module into the case, so it's more likely physical than electronic. The tank and its wiring are the first suspects.
Check the tank connections and the input and output coils resistance, should be about 25ohms and 900 ohms. If infinite resistance, the coil is broken.
search64
Right, thanks. Indeed, it's broken. Input coil is at 28 ohms but the output coil gives no resistance measurement. Do those things break easily?
papz
Yes, the coil wire is very thin and very fragile.
It often breaks in the visible part between the coil and header connector. If that's it you can try and repair it with solder but it's not easy because the wire pieces are very short.
Replacing the tank is the best solution.
pathein
Am currently all done with the passive parts across all cards and moving next to the transistors. I have labeled the leads of the transistors from papz built zip file pictures, according to the schematic for easy reference.

If there's any mistake in the pictures, do let me know.
n82558
Ok I may just have fatigue from staring at the board for too long but I can’t figure out where I’m supposed to connect the two conductor tinijax for the envelope detector. Can anyone point me in the right direction?

Also, was the sprague cap (or an alternative) for the output board included in the bom? I can’t seem to find it in my bag of parts. If not, does anyone know where to find one?

Thanks!
search64
You connect two of the three conductors to ground. The signal connection connects to card 10.

The Sprague is replaced with a 330n cap. It’s not as big as the 390n original.
n82558
Great, thank you.

I've currently got 3 cards done. No LEDs are lighting up yet so I decided to check the PSU rails to see if there are any shorts. Sure enough, if card1 is plugged in, 5v reads as 12v. I can't see any mechanical shorts on the card, anything else I should look for? Could it possibly be on the motherboard?
search64
Did you perhaps switch the 5V and 12V supply wires?
n82558
Nope, they’re at the proper voltages without card 1 installed. When card 1 is installed they’re both at 12v
papz
Possibly a faulty IC ? I'd try and replace them.
n82558
Yep, seems to be the 4009. Ordered some replacements online so I'll see if that fixes it. Everything else is working well so far though (fingers crossed)
papz
The caps are gone SlayerBadger!


I'll ship free of charge this soft caps set for sliders and switches to the first 208p builder who pms me. w00t



I think are the ones that Boops used to sell.
n82558
So I just finished the last of my cards and excitedly plugged in my easel but the output quality is horribly noisy (lots of static and crackling) regardless of which output its plugged into. Another strange behavior is that the large red output knob doesn't affect the volume on either the headphone out or the tinijax out. All other functions seem normal (although I haven't done any of the calibration procedure yet) so I'm guessing this is a problem with card 12? I know the card is expected to get hot but it gets very very hot to the touch, especially IC3. Can anyone suggest something I can do to fix this issue? I've attached a video of this behavior (sorry for the bad audio, its recorded from my phone's microphone), a direct recording from the headphone out, and images of card 12.

https://www.youtube.com/watch?v=fOcpuPG46us

https://soundcloud.com/lupin-tapes/208output/s-Sr2to





papz
There's something looking like a thin bridge of solder or flux between solder joints of contacts 3 - 4 and 9 -10 (rear side, starting from left) of the Molex connectors, these are the output and input of IC3 and IC1.
Clean this.
If this doesn't help, also check the male headers on the motherboard for shorts and the pots connections.
n82558
That was just some flux (and maybe a cat hair) but I cleaned it off and nothing changed. The output pot still doesn't do anything so I decided to poke around with the tip of a cable and noticed that I got clean audio off the pin of the pot thats closest to the bottom of the module. I then tested the resistance between that pin and the center pin of the pot with my multimeter and it read somewhere around 20M regardless of the pot's position. This suggests that the pot itself is bad, correct? I guess now I have to take the whole panel off to replace it. waah
papz
This looks like a faulty pot indeed. So bad.
Since in the corner, it should be possible to replace it without taking the whole panel off, only unsoldering the closest bananas and removing the mounting screws and other pots nuts to be able to slightly bend the PCB just enough to insert the new pot.
Cut off the faulty pot's legs will help remove it also.
n82558
So I was able to desolder the pot without removing the panel only to realize that I don't have a replacement so I just placed a smallbear order. The pot is definitely fried, when I test it with my multimeter it doesn't have any connection between pins. I tested the module without the pot though and it still has the same horrible distortion and static. Seems like the pot was only part of the problem...
papz
Maybe the pot was rather victim of the problem.
Did magic smoke escape ? Does the pot smell ?
n82558
Didn't get any magic smoke or burning smell. I got 3 replacement pots so at least I have some to sacrifice in case the module is burning out pots. I was trying to decipher the schematic but to be honest I"m not great at reading them. Where does the trace that the bottom pin on that pot lead to? It seems like the top pin goes to ground, and the wiper goes to a different trace on either side of the board. Really didn't want to but I guess I'll be taking the panel off tomorrow.
papz
Top pin : quiet ground
Wiper : card 12 pin 9
Bottom pin : R73 whose other end goes to R72 and to the reverb pot wiper. R72's other end goes to the monitor pot.

Here's a pic of the panel side.

n82558
Ok so I got a new pot and adding that didn't fix anything. I checked for shorts between pins on the header for card 12, and pins 5 and 15 are shorted to eachother. Is that correct? Something i've observed is that the output is quiet when I first switch on the module, but the noise, static and crackling increase the longer the module is on. What are the chances it could be a bad LM380?

EDIT: I removed the panel to do some more testing. Turns out the module is burning out the output pot, but I'm not sure why. Also, after further observation it seems that pins 5 and 15 are only shorted when reverb tank's input is attached to the motherboard. If I unplug the input from the tank those pins are no longer shorted. I've included pictures of the header for card 12 with the pins I'm talking about circled, as well as broader pictures of the output side of the motherboard. Does this make sense to anyone else because I'm driving myself crazy trying to figure out whats going wrong!









p.s. a special thanks to papz for all your assistance despite your claim on your website that you don't offer individual assistance! hihi
papz
This "short" is normal, it's in fact 26 ohms, the reverb tank's coil resistance, but your multimeter considers there's continuity because it's very low.

The output level pot is connected to IC1 4136. Does replace it help ?
n82558
I don't have any extra 4136 ICs so I swapped the one on card 12 with one on the enveloper and it doesn't change anything. Also, the enveloper continues to work as its supposed to so that seems to suggest that the IC that was on card 12 wasn't bad.
papz
Which voltages do you have on the pots terminals ?
n82558
The outer pins are both less than 1v but the wiper is almost 12v. Seems like there's a short to 12v somewhere?

Edit: This was with no pot installed.
papz
Do you still have 12V on wiper without card 12 plugged ?
n82558
Yes, I do.
papz
So the issue is on the motherboard.
Clean all the flux and chase it.
12V is on pin 14 of the pin header.
n82558
Found it! Or part of it...
I had motherboard c6 between pins 9 and 14 of card 12. I desoldered that and no more 12v on the output pot wiper. I think that cap is fried though because I get continuity between its leads when I test it with my meter. Of course I don’t have a replacement on hand...

Could I use a different style or value of cap there? At least for testing purposes?
n82558
Answered my own question; through another 15uf electrolytic in there (non-axial, bent on its side) and we’ve got beautiful clean sound! Now to put this dang thing back together...
papz
C6 is a filter cap between +12V and ground.
A 22µF common electrolytic cap should do the job.

Edit : great, glad it's fixed thumbs up
n82558
Alright so I'm really kicking myself now... very frustrating very frustrating very frustrating

I had a perfectly working easel (with the panel off) and was going to put everything back together but decided to wash it first. I cleaned all the cards and the motherboard with 90%ipa and water like I normally do and then blew them off with compressed air and a heat gun in some places. I then reassembled the panel and soldered all the banana jacks and waited a few hours till there was no sign of moisture left (or so I thought) and then powered it on. Nothing happened and I got the faint smell of magic smoke. Now the module won't do anything. I have all the cards off the motherboard and I don't see any visible shorts although there's some whitish residue in places (maybe from minerals in the water?).

Even with none of the cards installed, I'm getting a very strange behavior; when I turn on the module, noisy ground reads around 7.5v and then slowly decreases towards zero the longer the module is on. If it was reading at a consistent voltage I"d assume a short but the fact that it slowly decreases has me baffled. What could cause this?
papz
Ouch ! Sorry to read this.

The decreasing 7.5V on the noisy ground is normal behaviour, I just checked.

Did you check the power rails ?
n82558
Ok, thanks. at least I can stop looking for that problem!

Power rails are all good. I’m guessing some ic’s were shorted by residual moisture. When I get home I’m just going to insert the cards one by one until I find an issue.
papz
A short or fried component on a single card can cause the full module to stop working indeed.
If it does nothing, the 13.5V regulator circuit on card 3 is a culprit.
You'd be able to spot the damaged card(s) by smell if there was magic smoke.
n82558
Which ICs are involved in that part of the circuit?
papz
IC7 and Q2.

The schematics are your friends wink
http://www.portabellabz.be/images/208/schemas_208.zip
n82558
Thanks Papz. All good with the 13.5v regulator. I swapped out some 4066s and now the module is semi operational. Everything on the left side works as it should as do both oscillators but the LPGs are spotty. I noticed that they work intermittently if I put pressure on the cards. Is it possible that the alcohol/flux residue coated the headers/molex connectors and are blocking conductivity? It seems farfetched but all my solder joints look pretty solid.
papz
I don't think this coating is possible.

What's the LPG issue ? No sound ? Does the LED light up ?
n82558
Card 10 passes audio intermittently and the LED comes on intermittently. Card 11 does nothing unless I apply a lot of pressure and then the LED comes on but it still doesn't seem to pass audio. Also, the main outputs aren't working now, only the headphones.
captnapalm
n82558 wrote:
Card 10 passes audio intermittently and the LED comes on intermittently. Card 11 does nothing unless I apply a lot of pressure and then the LED comes on but it still doesn't seem to pass audio. Also, the main outputs aren't working now, only the headphones.


Were the ICs installed when you washed the cards? If so, I would carefully remove each one, make sure there's no water residue in the sockets (I'd blow them out) and re-seat. The fact that pushing on the card makes it work means there's a bad connection somewhere. If it's not in the sockets I'd start looking at all your solder joints next; you could have a cold solder that didn't cause a problem until you disassembled and stressed it. If you suspect the Molex connectors on the cards, re-seating them once should fix that.
papz
Just in case, IC3 on card 5 is also part of the LPGs circuit.
Puzzler
Whats the mystery about R52 100K on Board 3 - Envelope Generator Board?
papz
It's a load resistor of the 13.5V regulator circuit.
Puzzler
papz wrote:
It's a load resistor of the 13.5V regulator circuit.

OK, but where is it? hmmm.....
papz
In the bottom left corner of card 3, only labeled "100k", not "R52" on the drawing.
Puzzler
Which drawings are we using? Because Im working with this one Board 3. And there are only labels, no values.
captnapalm
Puzzler wrote:
Which drawings are we using? Because Im working with this one Board 3. And there are only labels, no values.


Papz has some of his own card pics with additional notes, which you can download from his web page:
http://www.portabellabz.be/images/208/cards.zip
Puzzler
Rockin' Banana!
Puzzler
Are these vactrolls correctly installed?
needspeed
Puzzler wrote:
Are these vactrolls correctly installed?


I will look at mine later but hopefully someone beats me to it......Steve
papz
Yes they look correctly installed.
Puzzler
Thanks fo rthe halp.
Another question:


Whats supposed to be connected to these?
I connected the reverb tank signal output to card 12. But what are these 2 spots for?

And what reference is TP1 and TP2 for?

And for the pa726 it says:
"Use a 12k resistor if the supply is +/-15V or a 10k resistor if +/-12V"
Supply is the AC/DC Adapter right?
papz
Just ignore these spots and the test points (TP).

The pA726 for 208's supply is +/-15V (supply is the power rails, not the adapter), the link in the 208 build notes sent to info for an older pA726 revision, sorry, I just corrrected it : here is the good one for this revision : http://www.portabellabz.be/images/pa726/pa726-208.pdf
trimix
gawd I feel like a nooob.

Building the black 208/218 set, and ready to apply power for the first time soon. Yes I see the 6 points for power connection. But off the board, where is the power coming from... ie, what is the PSU to use?
I have this card still to build: (photo) Is this what the mother board and 218 keypad should plug into? If so, what power is supplying this card and how?

Then if this set is built into a case, are we adding external linear or switching power supply units as well? What configuration should they be? If you have pics of your setup, that would be really helpful. Kinda trying to not blow anything up at this point....
captnapalm
trimix wrote:
gawd I feel like a nooob.

Building the black 208/218 set, and ready to apply power for the first time soon. Yes I see the 6 points for power connection. But off the board, where is the power coming from... ie, what is the PSU to use?
I have this card still to build: (photo) Is this what the mother board and 218 keypad should plug into? If so, what power is supplying this card and how?

Then if this set is built into a case, are we adding external linear or switching power supply units as well? What configuration should they be? If you have pics of your setup, that would be really helpful. Kinda trying to not blow anything up at this point....


If you build out the board you have, then you only need to power it with a 12v wall brick like this:

https://bit.ly/2K1mUXG

You just connect it to the +12v and ground on the 211 board.
Puzzler
papz wrote:
Just ignore these spots and the test points (TP).

The pA726 for 208's supply is +/-15V (supply is the power rails, not the adapter), the link in the 208 build notes sent to info for an older pA726 revision, sorry, I just corrrected it : here is the good one for this revision : http://www.portabellabz.be/images/pa726/pa726-208.pdf


Thanks for your help!

And another question seriously, i just don't get it
https://www.youtube.com/watch?v=G7E0jS7rT_8

Some kind of clipping/clicking is audible.
It seems as if its a pulse which marks the beginning and end of an envelope?!

Loudest when "SIGNAL ROUTING" switch on top position.
Loudest audible on Channel B, but also in Channel A.

Now I dont know if this is an error or "fixable" via calibration or what is the reason for this? sad banana
papz
Maybe this could help seriously, i just don't get it
https://www.muffwiggler.com/forum/viewtopic.php?t=201116&highlight=

Edit : I just checked on the 3 208s I have on hand, this occurs too but very slightly when EG and pulser are running, not sure how loud it is in yours from your video.
That being said, I rarely use the LPG2 at full level with no audio signal sent into it, probably why I didn't notice it before. Mr. Green
Puzzler
Yes this "208r PULSER leaking in audio channel (and ENV too)" describes my problem quite well.

I havent tested the bleeding workaround yet. Will give it a try.
But what else could be done?
papz
Which PSU are you using ?
I just noticed that this clicking is louder with a 211 board + Cincon brick PSU like the one pictured below. This PSU also causes hum at the outputs. Not the first time I have problems with this PSU, it caused interferences in the CO of another 208 I worked on recently. I've seen 2 only (not my builds) so far, both cause problems, and I've heard about other issues with these a.o. from Captnapalm. Likely not the best design.
With the same 208 and a Mean Well PD-2515 + the mini distroboard available on my website, the outputs are perfectly quiet of hum and this clicking is very slight.

So you could try another PSU.

Puzzler
I bought from samodular, which came with such a matte black distribution board + 12V AC/DC adapter.

The Mean Well PD-2515 is powered by 230V(EU) and the MW powers then the mini distribution boards, right?
papz
Yes
trimix
papz wrote:

@trimix : order well received thanks, I'll ship today. The pA726s come with the 208p PCB set, maybe did you buy a 208r ? I don't seem to have a record of a 208p purchase by you, but if you did and I forgot these in the set, please pm me and I'll refund you the pA726 purchase.


I received the pA726 cards - thanks. the kit I bought was the Ltd Edition Black, Rev 2.1 which includes the 218 as well. Actually, I'm building these for a friend as well, so two sets were sent to me. There are some small chicklets included, but not the pa726 like the ones I received. Kinda confused, but haven't got to that board in the build yet.
papz
The chiclets are another µA726 replacement board supplied with the 218r, for a smt SSM2212.
You can use these or the pA726 at your best convenience, but I recommend the pA726 (of course wink).
papz
A possible cause of the problems with the 211 power board may be that all the grounds are interconnected : there's continuity between the quite and noisy grounds and the Cincon brick's -.

I replaced the 211 board with an Artesyn AEE00CC18-LS +/-15V DC/DC converter that I had on hand, powered with the Cincon brick's 12V, connected to a mini distro board with 7805 and 7812 (I didn't use the Cincon's 12V to power the +12V rail directly) and with well separated Q and N grounds : the 208 is now perfectly quiet and the LPG2 clicking is barely noticeable.
Puzzler
If you put the Pre AMp switch to "lo" and Signal Routing to middle, you also cant hear the clicking.
papz
If you patch an audio signal to the preamp input you shouldn't hear the clicking either, regardless of the switch position. wink
Siri
papz wrote:
A possible cause of the problems with the 211 power board may be that all the grounds are interconnected : there's continuity between the quite and noisy grounds and the Cincon brick's -.

I replaced the 211 board with an Artesyn AEE00CC18-LS +/-15V DC/DC converter that I had on hand, powered with the Cincon brick's 12V, connected to a mini distro board with 7805 and 7812 (I didn't use the Cincon's 12V to power the +12V rail directly) and with well separated Q and N grounds : the 208 is now perfectly quiet and the LPG2 clicking is barely noticeable.


Hi papz, How are the quiet ground and noisy ground separated on your mini distro pcbs? On the one with 4 tabs (from pictures) i can see a place to put a component that connect the two and on the two tabs one i don't see anything... How do you do, if i may ask?
papz
Q and N grounds are not connected on the mini distro boards.
I added this emplacement on the one with 4 tabs just in case someone ever needs to short them but it should be left empty in most cases.
cygmu
papz wrote:
Q and N grounds are not connected on the mini distro boards.
I added this emplacement on the one with 4 tabs just in case someone ever needs to short them but it should be left empty in most cases.


This is exposing my lack of understanding of the grounding scheme.

On the 208 mini distro boards (2 tabs), what do Q and N connect to? Presumably at least one of them connects to the 0V input?
papz
On my 208 mini distro board the noisy ground is connected to the 2 "N" pads only.
Shorting quiet and noisy grounds on the distro board may cause a slight background hum and interferences. I'm not an engineer and can't explain why but I noticed it.
In the 208 quiet and noisy grounds are shorted on board 12, not on the MB. There's certainly a reason why Don Buchla did it this way.
cygmu
Interesting. I remember the note on the Board 12 schematic now which says that Q and N are shorted there, from some version onwards, or something like that.

I had always assumed this was in addition to them being connected at the PSU -- because otherwise how did the previous versions work at all?
papz
Maybe the previous versions worked with a slight hum and interferences ? lol

Here's the note :

Puzzler
papz wrote:
Maybe the previous versions worked with a slight hum and interferences ? lol

Here's the note :



So this note explicitly says to remove the feedthrough Q and N are shorted.
But didnt you say shorted Q and N is the reason for feedthrough?
Or did I miss something?

Also you said patching the pre-amp would eliminate feedthrough, isnt it somehow possible to get a workaround somewhere there (at the pre-amp), without need of an actual patch?
papz
The note explicitly says Q and N should be shorted on this board (that is board 12).
Not on the distro board.
This confirms my previous posts.

The preamp is not meant to be used at full level routed to the LPG at full level routed to the output channel at full level without any audio signal present at its input. If you do it like this, it's not only a pointless setting but it will result in this slight clicking, even if the Q and N are not shorted on the distroboard. This is normal behavior.
The preamp is meant to feed audio into the 208. With an audio signal patched into the preamp input - which is the normal and only way it should be used - the clicking will disappear.
trimix
I'm trying to find the tantalum capacitor for c2 of Card 12...supposed to be 390uF (12v) Axial. It doesn't seem to exist anymore on the interwebby thing. What have you guys used, and where did you get it from? Is there a substitute?
captnapalm
trimix wrote:
I'm trying to find the tantalum capacitor for c2 of Card 12...supposed to be 390uF (12v) Axial. It doesn't seem to exist anymore on the interwebby thing. What have you guys used, and where did you get it from? Is there a substitute?


some people use a 330uf like Dave Brown mentions:
https://modularsynthesis.com/roman/buchla208v2/208spss.htm

I have several of the original NOS ones. Send me a PM if you’d rather have one of those.
papz
This cap's value is not critical and any 330µF electrolytic is fine indeed.

On board 12 too, the expensive big inductors can be replaced by another 2.2µH inductor, for example Taiyo Yuden CAL45TB2R2K.
trimix
Ah good advice. thank you both. I hadn't checked the DB mods yet as I was just compiling an initial order from the BOM.
dingebre
Hi everyone. I am just coming to this project, I've ordered a set of 208 PCBs, a ToolBox, and BOB from Portabellabz. I've been reading all the MuffWiggler threads I can find on the topic as well as Dave Brown's excellent site.

I would like to clear up one question. Has the pin out of the 2N2907A on card 3, EG, been changed or do I still have to swap the base and collector leads? The thread that Don T started for Roman's PCBs starts out saying the newest version of Roman's PCBs correct this so the swap is not needed. What about on Papz's PCBs? ( I don't fully understand the interaction between Roman and Papz and their PCB sets)

https://www.muffwiggler.com/forum/viewtopic.php?t=174863&start=all&pos tdays=0&postorder=asc

Thank you.

David
papz
Hi

The 208p PCBs are error free. No builder fix is needed, you just have to mount the parts as shown on http://www.portabellabz.be/images/208/cards.zip

The other differences with the 208r are listed in the FAQ http://www.portabellabz.be/208pcbfaq.html

Happy building.
dingebre
papz wrote:
Hi

The 208p PCBs are error free. No builder fix is needed, you just have to mount the parts as shown on http://www.portabellabz.be/images/208/cards.zip

The other differences with the 208r are listed in the FAQ http://www.portabellabz.be/208pcbfaq.html

Happy building.


Thank you!

David
tronotape



Has anyone made a reference to what these connectors correspond to on the PCB? (Not specific to these codes, just in general including S1-, S2-, and S3-)
Sammus
papz wrote:
Or this way.
Legs can be extended with wire if needed.



Using a dual vac means there is only one led instead of 2 in series when using 2 vacs. I thought one wouod need to add a current limiting resistor to the led side to compensate for the voltage drop normally present from the second led? Why is it not the case? smile (asking for curiosity, mostly)
tarandfeathers
tronotape wrote:



Has anyone made a reference to what these connectors correspond to on the PCB? (Not specific to these codes, just in general including S1-, S2-, and S3-)


They don't correspond to anything on these, or the RF boards. The original used a ribbon cable on an IDC header to connect to the banana jacks at the bottom of the panel, I presume S is the connector, the second number is the row and the third number is the pin on that row. So you can think of them as the contact points that the banana jacks connect to.
tarandfeathers
Sammus wrote:
Using a dual vac means there is only one led instead of 2 in series when using 2 vacs. I thought one wouod need to add a current limiting resistor to the led side to compensate for the voltage drop normally present from the second led? Why is it not the case? :) (asking for curiosity, mostly)


Buchla normally drive the LEDs in their optocouplers using a voltage controlled current source, so, within the capabilities of the supply rails, a given CV will result in a particular current, regardless of the value of the dropping resistor, or in other words the drive circuit will force the dropping resistor to develop the required voltage across it to ensure a particular current flows. Remember that LEDs are roughly speaking constant voltage devices where once you get to turn on the brightness depends not on the voltage across the led but on how much current is flowing through it, so a current source is a better way to drive them for control applications. The series resistor is there for overload protection only.
papz
Sammus wrote:
Using a dual vac means there is only one led instead of 2 in series when using 2 vacs. I thought one wouod need to add a current limiting resistor to the led side to compensate for the voltage drop normally present from the second led? Why is it not the case? smile (asking for curiosity, mostly)

Good question.
I did some tests comparing boards 11 and 12 with dual and single vactrols and noticed no significant difference, at least not bigger than what one could expect from the vactrol tolerance.
Increasing R40's value (in series with the vactrol LED) even makes the LPG sound less snappy.
dksynth
Alrighty, I'm here hat in hand.

CO problems, tears!

First shot at building one of these, loving the papz boards and the panel is fantastic quality.

I don't 100% understand the CO operation yet, it seems the expo on card 7 runs two separate oscillator cores?

My symptoms are as follows:

CO outputs only very thin spike in timbre is down.
With timbre all the way up, waveshapes come through but not really the right ones.

It seems like my card 9 isn't outputting a triangle... gone through all values and solders, can't find anything, so maybe I am missing something about how it works.

here are some scope shots:



This is from card 8, Pin 9 in blue is supposed to be the card 9 triangle but looks quite lopsided, pin 15 yellow is the other triangle



here's the output of the sine shaper at IC4 pin 3 with TIMBRE up in yellow against pin 14 square wave in blue.

It seems like the sine is always mixed with everything else, so with my sine stuck not really working it results in these thin pulse waveforms. Looks like the two COs are in sync, but that lopsided triangle is causing havoc with the sine shaper and sending everything sideways.

any help, pointers welcome, thanks!
papz
Can you get a proper sine wave with timbre and waveshape to 0 adjusting the card 8 trimmer ?
If not, swap Q1 or change R41's value.

The CO is 2 different oscillators indeed.
There are some useful notes on how it works on https://modularsynthesis.com/roman/buchla208v2/208spss.htm
Sine is always present at the CO output, the other waveshapes are added to it.
Timbre affects the triangle and sine only.
dksynth
Thanks for you input papz,

No sine at all unless timbre is up.

Which now that I think about it.... sine must be dead somewhere. Timbre is the sine or triangle modulated by each other? A static voltage coming out of the sine would explain the other symptoms.

Q1 idss tests as 0.8 within spec and I put a trimmer for r41
papz
Did you try and replace the ICs ?
Is IC2 on card 8 a 4016 or 4066 ? 4066 works better than 4016 everywhere in the 208 except on card 8 where it causes problems in some builds.
dksynth
I did make that mistake! But I already found that it, put the 4016 in card 8. it was even worse before I found that.... CO wasn't making much sound at all.

I'm going to try and replace some ICs when I get back into the shop tonight if I can't find where the sine is going squirrely.

I do think I may have some bad LM301s, I have a very very old tube of them I found in the shop I was using and one of them on card 9 (IC6) got a bit hot. Not too hot to handle, no hard shorts and voltages were fine but I replaced it and the new one is running cool. Maybe some of the other ones are suspect as well.

-dk
dksynth
Got it! Problem on card 9, ins an outs of that 4136 weren't making sense. Replaced it and the 301s for good measure.

All working now smile
papz
thumbs up
tronotape


Is there suppose to be a connection between pins 5 and 6 on board 2? Bottom photo is my board.
papz
Indeed, this is a missing trace, thanks for finding it. IC1 pins 5 and 6 are well connected in the schematics.
It remained unnoticed so far because the panel random outs work without it.
It's related to the random output 1 on the program card.

Damn, so my PCBs are no longer error free. cry
aabbcc
papz wrote:
Indeed, this is a missing trace, thanks for finding it. IC1 pins 5 and 6 are well connected in the schematics.
It remained unnoticed so far because the panel random outs work without it.
It's related to the random output 1 on the program card.

Damn, so my PCBs are no longer error free. cry


Please update your website with this smile I will be buying a kit next month or so and will for sure have forgotten all about this by then razz
papz
Of course, I updated the build notes http://www.portabellabz.be/images/208/208%20build%20notes_final.pdf

Thanks for your future purchase wink
trimix
papz wrote:

Good question.
I did some tests comparing boards 11 and 12 with dual and single vactrols and noticed no significant difference, at least not bigger than what one could expect from the vactrol tolerance.
Increasing R40's value (in series with the vactrol LED) even makes the LPG sound less snappy.


How's this for a roundabout and half-related question: I asked about this quite a long time ago, but there was no definitive answer.
Has anyone ever experimented with using different Vactrols? The reason I ask is because I have a lot of VTL5C1's on hand. Could I use these instead of the specified VTL5C3's (except, of course, where dual VTL5C3s are indicated) without problems? It's not like they're THAT accurate in their performance!
...or are they ? seriously, i just don't get it
papz
VTL5C1's might upset calibration, I serviced a 208 built by someone else who used VTL5C1's at various emplacements and couldn't calibrate it properly until I replaced some with a VTL5C3. Maybe another VTL5C1 would have been ok, tolerance is so large, but I didn't test, having no VTL5C1.

Anyway feel free to experiment, there's no risk of damage.
The important thing is you are happy with your 208's sound and behavior. wink
wedaman
Hello everyone.
I appreciate the dedicated work of papz.

Please help me install switch 11 (DIGIKEY PART # CKN 1008 - ND) on the motherboard.

Is the correct answer as shown below?
ON (triggerd) - OFF (off) - Momentary ON (one)
captnapalm
wedaman wrote:
Hello everyone.
I appreciate the dedicated work of papz.

Please help me install switch 11 (DIGIKEY PART # CKN 1008 - ND) on the motherboard.

Is the correct answer as shown below?
ON (triggerd) - OFF (off) - Momentary ON (one)


Yes that's correct. The momentary position should be when you depress the switch downward to the "one" setting.
wedaman
captnapalm wrote:
wedaman wrote:
Hello everyone.
I appreciate the dedicated work of papz.

Please help me install switch 11 (DIGIKEY PART # CKN 1008 - ND) on the motherboard.

Is the correct answer as shown below?
ON (triggerd) - OFF (off) - Momentary ON (one)


Yes that's correct. The momentary position should be when you depress the switch downward to the "one" setting.



Thanks! captnapalm.
tronotape
Should the fine tune knobs be set at noon when calibrating?
papz
When calibrating I set the CO fine tune fully CCW to make sure the lowest frequency possible is about 55Hz, if lower instability occurs sometimes, and the MO fine tune fully CW to have a comfortable range in audio frequencies.
wedaman
Hello everyone.

It is a question about calibration.
Where are the oscilloscopes connected when calibrating Buchla 208?
The ground is easy to understand. But at which point should each calibration be connected?
papz
Hi
I monitor the audio outputs for calibration.
wedaman
papz wrote:
Hi
I monitor the audio outputs for calibration.


I see. Thanks. Rockin' Banana!
Chaotic
First power up and testing. Love this machine. It seems like everything is functioning as it should. I have not calibrated it yet Rockin' Banana!
papz
thumbs up
Chaotic
I can almost say I have finished my 208 It's peanut butter jelly time!
Only one problem remaining.
Sometimes when I turn up headphone pot strange things happens. Distortion, noise, crackling and audio drop. The tuning is also affected. Turning down the pot restore the sound. Both line out and headphone are the same.
Visual inspected the values on the card.

My first thought was the headphone pot but I have tried another card 12 and then its ok.
Some ideas where I can start?
papz
Inspect solder joints.
Check values with a multimeter, comparing with the good working card 12.
tarandfeathers
Also measure across the monitor volume pot and check if there is DC across it.
fg
hello, simple question about the dpdt on on on,
which one is the good A or B ?



thanx for your answer
davebr
Chaotic wrote:
I can almost say I have finished my 208 It's peanut butter jelly time!
Only one problem remaining.
Sometimes when I turn up headphone pot strange things happens. Distortion, noise, crackling and audio drop. The tuning is also affected. Turning down the pot restore the sound. Both line out and headphone are the same.
Visual inspected the values on the card.

My first thought was the headphone pot but I have tried another card 12 and then its ok.
Some ideas where I can start?

Your LM380s are likely breaking into high frequency oscillation. That will draw significant power and affect the tuning and explain the noise. I'm not sure why both the headphone and line outs are affected unless the oscillations are disturbing other circuits.

Lots of things can affect oscillations including wrong part values and soldering. Check all the part values around IC3 and IC4. The parts will get hot when oscillating and can burn themselves out. You can lift one end of R17 and R33 to disconnect the LM380s and verify the problem goes away (you won't have any headphone output). Then put one resistor back in and verify, then the other. You can probably isolate it to one of the channels. R17 drives IC3 and R33 drives IC4. You know the problem is on Card12 since you substituted it. Good luck.
papz
The on-on-on switches should be C&K (available from Mouser, Digikey) or Taiway (available from Small Bear) to match the PCB trace that makes the short needed between 2 lugs for this type of switch.
Another manufacturer's ones might not work because the short is between 2 other lugs and the pinout is different.

A on your pic.
fg
ok A

big thanx for your answer
Chaotic
davebr wrote:
Chaotic wrote:
I can almost say I have finished my 208 It's peanut butter jelly time!
Only one problem remaining.
Sometimes when I turn up headphone pot strange things happens. Distortion, noise, crackling and audio drop. The tuning is also affected. Turning down the pot restore the sound. Both line out and headphone are the same.
Visual inspected the values on the card.

My first thought was the headphone pot but I have tried another card 12 and then its ok.
Some ideas where I can start?

Your LM380s are likely breaking into high frequency oscillation. That will draw significant power and affect the tuning and explain the noise. I'm not sure why both the headphone and line outs are affected unless the oscillations are disturbing other circuits.

Lots of things can affect oscillations including wrong part values and soldering. Check all the part values around IC3 and IC4. The parts will get hot when oscillating and can burn themselves out. You can lift one end of R17 and R33 to disconnect the LM380s and verify the problem goes away (you won't have any headphone output). Then put one resistor back in and verify, then the other. You can probably isolate it to one of the channels. R17 drives IC3 and R33 drives IC4. You know the problem is on Card12 since you substituted it. Good luck.


Thanks. Tried my card on my friend´s 208 and it works. Couldnt see something wrong but resoldered all the solder joints and now its working. It had something with the 380s to do. They got very hot. Checked all the component values and they were ok
Now I hear some crosstalk from the osc and pulser with all signal pots down. I have read about it somewhere so now I have to read all the threads again. hihi

Edit #1: Tomorrow I will try to put a resistor in series to the led on the pulser. Maybe that will solve the leaking from it?
And try another psu. Now Im using a Blacet 500mA. I have a 800mA I can try.

Edit #2: The resistor solved most of the clicks from pulser and envelope.
Another psu had nothing to say. But I tried a shorting between noisy and quiet ground on the distro board and most of the CO leakage disappeared.
I know this should not be done but it seems like the leakage is better. Not gone but less audiable
Chaotic
The only issue now is the bleeding. Not only the MO, but the CO too.
It's quite noticeable when all pots and slider pointed at zero. And it disappear when I crank the output pot to about 4.
I tried to swap card #12 with my friend´s roman card and then, no bleeding. Quiet.
I have checked the component values and they are the same.
Only the capacitor types are different. (same values)
Some ideas?
[img][/img]
papz
Are your cables to the distroboard thick enough ?
Chaotic
papz wrote:
Are your cables to the distroboard thick enough ?

I have used 1mm2 (AWG 17)
papz
This should be enough indeed.
The difference in behavior swapping cards 12 is weird, I'm not sure the capacitor type is in cause as long as the values are ok.
Since it's more noticeable when all pots and sliders are to 0, it looks ground related. Compare resistance between the cards 12 groundplane and Q and N grounds on the MB, with the module disconnected from the distroboard (shorted Q and N on this, right ?).
fg
hello, it's done and working !!!

just small question about a strange behaviour from the sequencer in "both mode" only, everything is ok in "front panel mode"
see the picture below.



any ideas ?

thanx a lot for all
papz
Did you use modern 4013's ? Some cause stages # errors. If yes, try and swap them with old ones such as V4013D, available on ebay .
fg
yes, i use a modern one i will try an old one

but it s working very well in "front panel mode" ? just instable in "both mode"
i think that is strange.

the rest is perfect !!! thanx again
papz
There are dual outputs stages for the panel settings and for the program card slot settings. Your problem is probably related to the card one and affects the global performance when in both mode because both stages are active.
If swapping the 4013s (there are 2) doesn't help, there's maybe a short or bad contact somewhere.
fg
hello

I hear a little "the pulser" in the co, is there a solution to this little problem ?

a trim to turn ?

but may be is it normal, this is the first time that i use this machine.
100% noob

thank you again
papz
Let me quote the build notes. wink
http://www.portabellabz.be/images/208/208%20build%20notes_final.pdf

Quote:
LEDs and bleed
The LEDs, mostly the pulser's and envelope's ones, affect the oscillators pitch. This can be
attenuated by the addition of series resistors. To add a resistor to the pulser's and envelope's LED, cut the
PCB trace between the 2N1711 and Molex connector (there's only one, on the solder side) of
boards 3 and 4 and bridge the cut with a resistor.
Add a resistor in series with the other LEDs can be done on the motherboard the same way.
Depending on the LEDs you use, select a resistor in order to achieve the best possible
compromise between LED brightness and oscillators drift.
With the LEDs suggested above, 10k resistors are fine.

Sequencer
If the sequencer sometimes erraticaly skips a step, the 4013s are probably in cause. Some new
ones work fine, others don't. All the NOS ones I tested are ok.
fg
i reed build notes a long time ago but i forget, that's perfect !!! thanx
d'oh!

i command V4013D and after it will be ok i hope/think
fg
applause

10K is perfect !!!

thx
fg
for the information


v4013D won't fix my sequencer problem in "both mode" in the first time

very frustrating

i switched ic 2 to 4 and 4 to 2 and ok with 4 and 5 steps but problem with 3 steps

sad banana

thx
papz
thumbs up thanks for the info
4001s may have weird behavior, I had problems with some too, despite my IC tester says they are ok.
fg
i change the ic3 on card 1 and everyting seems ok now
It's peanut butter jelly time!
thanx again
Chaotic
My issue with this was solved with decoupling caps on half of the chips on card one nanners
papz
Yes decoupling caps can help too but I prefer to have good working ICs.
I can't help thinking that adding caps heals the symptom but doesn't cure the disease, despite it works.
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