208p build thread (papz's PCBs)

From circuitbending to homebrew stompboxes & synths, keep the DIY spirit alive!

Moderators: Joe., lisa, luketeaford, Kent

Post Reply
User avatar
papz
Super Deluxe Wiggler
Posts: 2995
Joined: Sat May 18, 2013 6:52 pm
Location: in a suitcase
Contact:

Post by papz » Wed Nov 06, 2019 4:27 pm

Card 12 should be in place because Q and N grounds are shorted on it, it doesn't work properly otherwise.

The best way to test/debug is to have a good working 208 on hand as a reference to compare. In case of issue swapping cards makes it much easier to locate the cause.

If you don't have access to another 208, follow the calibration instructions in the build notes and on Dave Brown's pages. The build threads are also a good source of tips and infos.
Last edited by papz on Wed Nov 06, 2019 4:34 pm, edited 1 time in total.
Finest EMS gear service and Music Easel/208 goodies

I'm not a synths dealer and I'm not aware of an inexpensive Synthi secret market, please don't ask me if I know one for sale.
I don't offer support of any kind to people attempting to build clones of EMS equipment.

kristop
Learning to Wiggle
Posts: 48
Joined: Thu Mar 24, 2016 12:31 pm

Post by kristop » Wed Nov 06, 2019 4:34 pm

Ah! Ok, I wondered if there were other things on some other cards that would be necessary. So if I put in Card 12 the sequencer might work? Sadly, no other 208 to play with. So I guess I'll just see how things go when I finish up the last of the cards.

Do I need all the banana jacks soldered to be able to calibrate/test properly? Or is there just a few needed to be able to calibrate? Just thinking if I have to trouble shoot a problem on the MB how much it could suck to have to desolder all of those.

Also, is there any reverb other reverb tanks that might work that might be available in North America? I don't have the reverb frame and was just going to mount it to the inside of my case (whatever that winds up being) so in theory there are options, but I can't seem to find much else that has the same input/output impedances as the 1BC2E, but it costs more to ship one of those over to Canada than the actual cost of one.
[bandcamp width=400 height=120 album=592621704 size=large bgcol=ffffff linkcol=0687f5 tracklist=false artwork=small]

kristop
Learning to Wiggle
Posts: 48
Joined: Thu Mar 24, 2016 12:31 pm

Post by kristop » Wed Nov 06, 2019 4:36 pm

papz wrote: The best way to test/debug is to have a good working 208 on hand as a reference to compare. In case of issue swapping cards makes it much easier to locate the cause.
Would having a BEMI easel on hand be helpful? I might have access to one of those.
[bandcamp width=400 height=120 album=592621704 size=large bgcol=ffffff linkcol=0687f5 tracklist=false artwork=small]

User avatar
papz
Super Deluxe Wiggler
Posts: 2995
Joined: Sat May 18, 2013 6:52 pm
Location: in a suitcase
Contact:

Post by papz » Wed Nov 06, 2019 4:41 pm

I prefer to test the fully built module.

The BEMI 208 is different in various aspects but it's better than nothing.
Finest EMS gear service and Music Easel/208 goodies

I'm not a synths dealer and I'm not aware of an inexpensive Synthi secret market, please don't ask me if I know one for sale.
I don't offer support of any kind to people attempting to build clones of EMS equipment.

User avatar
boops
Ultra Wiggler
Posts: 769
Joined: Mon May 06, 2013 6:06 am
Location: Paris France
Contact:

Post by boops » Wed Nov 06, 2019 6:02 pm

:hmm: its true ,i m well know as a bad and a no reliable wiggler :bananaguitar:
i ve built 1257 x 208R rev2 and have even sold some with some cards missing.(imho ,the easier debug to do) :mrgreen:



For the timbre ,begin with R3 gives me generally some good results,cheaper and easier than play with the vactrols.

papz wrote:
boops wrote:With my experience of the 208.for debugging
often ,we believe that all is fine ,on each card,but with a simple 4016
shorted,a flux short,a real short,a bad connection,etc somewhere in the 208,small problems appear,like a click in the env,an osc no stable etc.
After having debugged some 208 that you built and sold, I can only confirm this. :mrgreen:

R3 value depends on both the VT1 vactrol tolerance and the final user's own preference, therefore it should be selected on test as explained in the 208p build notes.
FS :custom buchla 203 style càbinet ,skiff new design,boat ,hardware for diy cabinet ,easel case ,new 1u to 10u to 56u and more. / New 208 buchla card 12 /
HQ small case buchla psu PCB
https://www.muffwiggler.com/forum/viewt ... 93#3118393
https://www.muffwiggler.com/forum/viewt ... highlight=

User avatar
papz
Super Deluxe Wiggler
Posts: 2995
Joined: Sat May 18, 2013 6:52 pm
Location: in a suitcase
Contact:

Post by papz » Wed Nov 06, 2019 6:33 pm

boops wrote:i ve built 1257 x 208R rev2
With mass production, a faulty unit is more likely to happen. :lol:
Finest EMS gear service and Music Easel/208 goodies

I'm not a synths dealer and I'm not aware of an inexpensive Synthi secret market, please don't ask me if I know one for sale.
I don't offer support of any kind to people attempting to build clones of EMS equipment.

User avatar
papz
Super Deluxe Wiggler
Posts: 2995
Joined: Sat May 18, 2013 6:52 pm
Location: in a suitcase
Contact:

Post by papz » Wed Nov 06, 2019 10:04 pm

I mean that R3 should be selected on test according to the VT1 vactrol's tolerance to fit the user's preference, not that one should play with the vactrols here.
There's no fixed value for "best performance", whether it's 8k2 or other, because the vactrols don't behave the same, with one a 1k8 resistor in R3 may give you a lot of foldings while another won't reach as many foldings even with a 10k resistor. This is why R3 value is not the same in the BOM - thus in the actual vintage 208 which was cloned - and in the schematics.
Finest EMS gear service and Music Easel/208 goodies

I'm not a synths dealer and I'm not aware of an inexpensive Synthi secret market, please don't ask me if I know one for sale.
I don't offer support of any kind to people attempting to build clones of EMS equipment.

kristop
Learning to Wiggle
Posts: 48
Joined: Thu Mar 24, 2016 12:31 pm

Post by kristop » Thu Nov 07, 2019 1:07 pm

Anyone...
kristop wrote: Also, is there any reverb other reverb tanks that might work that might be available in North America? I don't have the reverb frame and was just going to mount it to the inside of my case (whatever that winds up being) so in theory there are options, but I can't seem to find much else that has the same input/output impedances as the 1BC2E, but it costs more to ship one of those over to Canada than the actual cost of one.
[bandcamp width=400 height=120 album=592621704 size=large bgcol=ffffff linkcol=0687f5 tracklist=false artwork=small]

User avatar
papz
Super Deluxe Wiggler
Posts: 2995
Joined: Sat May 18, 2013 6:52 pm
Location: in a suitcase
Contact:

Post by papz » Thu Nov 07, 2019 1:29 pm

Any xBCxxxx tank can do the job.
More details on http://www.accutronicsreverb.com/
Finest EMS gear service and Music Easel/208 goodies

I'm not a synths dealer and I'm not aware of an inexpensive Synthi secret market, please don't ask me if I know one for sale.
I don't offer support of any kind to people attempting to build clones of EMS equipment.

User avatar
xahdrez
Wiggling with Experience
Posts: 297
Joined: Wed Apr 03, 2013 3:16 pm
Location: London

Post by xahdrez » Fri Nov 08, 2019 6:01 am

boops wrote:Check the isolation between each rails with an ohmmeter power off
a value under 200 ohms is suspect
Only just got a chance to check this last night - the resistance is > 200 ohms between all sockets on the unplugged 208, apart from between quiet ground and noisy ground (which is presumably to be expected given they are shorted on card 12?).

Going to do some more playing at the weekend if I get a chance and see what I can find, looks like there is plenty to experiment with before admitting defeat and getting a new power supply...but fairly sure that is what I'll end up doing eventually! :tu:

kristop
Learning to Wiggle
Posts: 48
Joined: Thu Mar 24, 2016 12:31 pm

Post by kristop » Mon Nov 11, 2019 11:59 am

Well it sort of works, basically everything works up to the CO which is quiet and distorted. When I turn up the levels for it the faders clip at 10. The one other thing is the switches for each step of the sequence don't do anything. They should turn steps off or on, no?

Will be swapping some ICs and looking at solder joints today. The MO sounds so sweet on its own. Can't wait to get this beast all working!
[bandcamp width=400 height=120 album=592621704 size=large bgcol=ffffff linkcol=0687f5 tracklist=false artwork=small]

User avatar
papz
Super Deluxe Wiggler
Posts: 2995
Joined: Sat May 18, 2013 6:52 pm
Location: in a suitcase
Contact:

Post by papz » Tue Nov 12, 2019 12:36 pm

Did you read the user manual ? It's worth doing. The answer to your question is on page 20.
http://www.portabellabz.be/images/208/m ... l_1974.pdf
Finest EMS gear service and Music Easel/208 goodies

I'm not a synths dealer and I'm not aware of an inexpensive Synthi secret market, please don't ask me if I know one for sale.
I don't offer support of any kind to people attempting to build clones of EMS equipment.

kristop
Learning to Wiggle
Posts: 48
Joined: Thu Mar 24, 2016 12:31 pm

Post by kristop » Tue Nov 12, 2019 3:32 pm

I did figure them out, I think they seemed to be weird because my oscillators weren't working right as well. Swapping some ICs got my CO working it seems, but I think the Modulator isn't working right still.
[bandcamp width=400 height=120 album=592621704 size=large bgcol=ffffff linkcol=0687f5 tracklist=false artwork=small]

User avatar
papz
Super Deluxe Wiggler
Posts: 2995
Joined: Sat May 18, 2013 6:52 pm
Location: in a suitcase
Contact:

Post by papz » Fri Nov 15, 2019 10:06 am

The modulator (card 5) is not the easiest to get properly working.
Dave Brown's notes and mods are very helpful.
Finest EMS gear service and Music Easel/208 goodies

I'm not a synths dealer and I'm not aware of an inexpensive Synthi secret market, please don't ask me if I know one for sale.
I don't offer support of any kind to people attempting to build clones of EMS equipment.

User avatar
sanders
Veteran Wiggler
Posts: 714
Joined: Tue Feb 03, 2009 4:42 pm

Post by sanders » Fri Nov 15, 2019 3:24 pm

tarandfeathers wrote:
sanders wrote:Can anyone recommend a higher value current limiting resistor
The only way to be sure is to work it out for the specific LEDs you have used.
I understand. However, I've now realized that the cause of my issue is more likely that I didn't read Papz notes carefully enough in regard to his low-brightness LED recommendation. I mistakenly thought he was endorsing the "soft LEDS" from the BOM. But if I had paid more attention, I would have seen that he was instead recommending an even softer LED (Mouser part 696-SLX-LX3044HD) than the one in the BOM. Doh!

I'm guessing Papz recommended "soft LED" will satisfy my issue with the BOM LEDs. Unfortunately, it's not an easy exercise replacing all the LEDs now that my jacks are all soldered in place, etc. But, I'll get to it eventually.
tarandfeathers wrote: As for the clipping/saturating behaviour of the LPGs, I would hazard a guess that this is to do with the output FETs. If you bought these from utsource/ebay/aliexpress/whatnot I'd try something from a more reputable supplier.
Problem solved. I've found out the hard way that there are more than one pin-out for many of the rare transistors used in this build. If I had to do it again, I'd know to stick to suppliers that have already been vetted here. I believe the problem has more to do with part and pin-out variation, than it does with "bad" parts or suppliers (at least in my cases).

User avatar
sanders
Veteran Wiggler
Posts: 714
Joined: Tue Feb 03, 2009 4:42 pm

Post by sanders » Fri Nov 15, 2019 3:48 pm

papz wrote:...R3 should be selected on test..
There's no fixed value for "best performance", whether it's 8k2 or other, because the vactrols don't behave the same, with one a 1k8 resistor in R3 may give you a lot of foldings while another won't reach as many foldings even with a 10k resistor.
I have been testing different values here and notice quite a bit of variation, as you describe. However, what I'm hearing in regard to the change of R3 values is what I'd describe as a change in the character of the folding sound. What I'm not yet able to alter, for reasons unknown to me, is a change in the degree or amount of the Timbre effect.

The entire range of my Timbre effect happens between 0 and 2.5 on both the Timbre slider, and Timbre CV input slider. I don't believe R3 has any impact on this slider behavior.

At the highest amount of Timbre, starting at 2.5 on the slider, it's practically like metal noise. R3 effects the character of this extreme folding sound quite a bit, but it's just like different flavors of metallic noise, as I lower the resistance. When the resistance is too low, it won't fold at all.

I guess I need to try a different Vactrol?

User avatar
papz
Super Deluxe Wiggler
Posts: 2995
Joined: Sat May 18, 2013 6:52 pm
Location: in a suitcase
Contact:

Post by papz » Sat Nov 16, 2019 7:13 am

Did you try and swap IC1 (4136) on card 7 ?
Finest EMS gear service and Music Easel/208 goodies

I'm not a synths dealer and I'm not aware of an inexpensive Synthi secret market, please don't ask me if I know one for sale.
I don't offer support of any kind to people attempting to build clones of EMS equipment.

kristop
Learning to Wiggle
Posts: 48
Joined: Thu Mar 24, 2016 12:31 pm

Post by kristop » Sun Nov 17, 2019 1:15 pm

I seem to be having a similar issue. My Timbre changes around the middle of the slider, but it really just seems to cross fade over maybe 10% of the slider range right around the middle between two different sounds. I don't have a 4016 to try out. Also the wave know seems to mostly just kill the level of my CO as I turn it CW. Would calibration help with this or do I need to chase down an issue still?
[bandcamp width=400 height=120 album=592621704 size=large bgcol=ffffff linkcol=0687f5 tracklist=false artwork=small]

User avatar
papz
Super Deluxe Wiggler
Posts: 2995
Joined: Sat May 18, 2013 6:52 pm
Location: in a suitcase
Contact:

Post by papz » Sun Nov 17, 2019 1:26 pm

This sounds like an issue and I'm afraid calibration won't help.
Finest EMS gear service and Music Easel/208 goodies

I'm not a synths dealer and I'm not aware of an inexpensive Synthi secret market, please don't ask me if I know one for sale.
I don't offer support of any kind to people attempting to build clones of EMS equipment.

kristop
Learning to Wiggle
Posts: 48
Joined: Thu Mar 24, 2016 12:31 pm

Post by kristop » Sun Nov 17, 2019 1:34 pm

Thought likely. Have had good luck fixing things changing chips. Hopefully I can find a 4016 locally. I don't think I thought to order one... I don't think.......
[bandcamp width=400 height=120 album=592621704 size=large bgcol=ffffff linkcol=0687f5 tracklist=false artwork=small]

User avatar
sanders
Veteran Wiggler
Posts: 714
Joined: Tue Feb 03, 2009 4:42 pm

Post by sanders » Mon Nov 18, 2019 9:53 pm

papz wrote:Did you try and swap IC1 (4136) on card 7 ?
I swapped out IC1 and it seemed to make some positive impact; But ultimately, I found once again that the issue came down to a bit of sloppiness my part.

I went back through Dave Brown's calibration instructions and after paying closer attention to CO offset, CO waveshape, CO timbre and how they inter-relate, I managed to get the timbre controls working very well.

Careful adjustment of these three controls completely tamed the extreme metallic end of the Timbre, and now the front panel controls sweep beautifully (with maximum Timbre sounding at the top of the slider, as one would expect). I believe most of the offending sound must have been a result of the CO beating against itself as the Timbre effect was introduced.

Everything seems great now; scale and tuning are very good and were no problem to trim once I made the resistor substitutions on Dave Brown's build page. Love this instrument-- thanks very much Papz!

User avatar
sanders
Veteran Wiggler
Posts: 714
Joined: Tue Feb 03, 2009 4:42 pm

Post by sanders » Tue Nov 26, 2019 6:59 pm

My Sine wave knob could probably work better. I don't get a very gradual fade between waveforms-- mine works more akin to a switch that crchanges over to Sine Wave at the very end of the knob travel (basically where the sine wave graphic is on the panel).

Does this response mostly come down to Vactrol selection?

User avatar
papz
Super Deluxe Wiggler
Posts: 2995
Joined: Sat May 18, 2013 6:52 pm
Location: in a suitcase
Contact:

Post by papz » Tue Nov 26, 2019 7:42 pm

Probably.
Finest EMS gear service and Music Easel/208 goodies

I'm not a synths dealer and I'm not aware of an inexpensive Synthi secret market, please don't ask me if I know one for sale.
I don't offer support of any kind to people attempting to build clones of EMS equipment.

User avatar
captnapalm
Veteran Wiggler
Posts: 597
Joined: Tue Aug 31, 2010 3:37 pm

Post by captnapalm » Tue Nov 26, 2019 11:04 pm

Yes I had one that was really sudden, and switching out a vactrol made it gradual for me.

kristop
Learning to Wiggle
Posts: 48
Joined: Thu Mar 24, 2016 12:31 pm

Post by kristop » Wed Nov 27, 2019 1:50 pm

sanders wrote:My Sine wave knob could probably work better. I don't get a very gradual fade between waveforms-- mine works more akin to a switch that crchanges over to Sine Wave at the very end of the knob travel (basically where the sine wave graphic is on the panel).

Does this response mostly come down to Vactrol selection?
Mine works fairly evenly, but when blend in the triangle wave I pretty much lose all volume.

Also, after swapping out to a 4016 on card 8, I've been noticing my sequencer skipping step 5 every now and then. doh!

Has anyone set theirs up to track 1v/oct? I was trying to calibrate mine to last night and couldn't get it anywhere near.
[bandcamp width=400 height=120 album=592621704 size=large bgcol=ffffff linkcol=0687f5 tracklist=false artwork=small]

Post Reply

Return to “Music Tech DIY”