208p build thread (papz's PCBs)

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Post by papz » Wed Nov 27, 2019 2:34 pm

It's hard to figure out how swapping the 4016 on card 8 would cause the sequencer to skip a step. You probably rather didn't notice it before. This issue is related to the 4013s or 4009 on card 1 in most cases, as explained in the build notes.

For 1 and 1.2 V/oct tracking, some resistors values should be adapted compared to the BOM, as explained in the build notes too.

http://www.portabellabz.be/images/208/2 ... _final.pdf
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Post by kristop » Thu Nov 28, 2019 3:06 pm

I was surprised that it started doing it as well, I've been using it for hours prior to changing to the 4016 without it ever skipping a beat but noticed it do it multiple times within a couple of minutes now. I also think my CO is prone to distortion now with the 4016. Going to swap back to the 4066 I last had in as I don't think the Timbre worked any less better than it does now and see what that does to things.

Was going to make the resistor changes in the build notes this weekend.
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Re: 208p build thread (papz's PCBs)

Post by jasonjasonson » Mon Jan 13, 2020 7:33 am

Allright!

I'm also trying this build!
Finished the motherboard and card 4 (pulser) and 3 (eg & 13.5V). I'm taking my time, better safe than sorry 8-)

Hooked them both up last night and I wonder if they work correctly (I've read the manual and watched some youtube video's but I'm not really sure).

The pulser seems to work, I can kickstart it and let it self cycle on low and high frequencies. However the EG seems to influence the Pulser and I'm not really sure if it should do that?

1) When I flip the EG Trigger Mode Switch to "Pulser", if attack/duration/decay are all the way up (short), the pulser triggers the envelope, as expected (EG mode is "Transient"). But when I move the Pulser frequency slider all the way up (really fast), the Pulser LED goes dim (it doesn't do that if the EG Trigger Source is set to Keyboard or Sequencer) & the EG LED also goes DIM (and fades out all the way). Seems strange?

2) When I raise the duration-slider in combination with a fast Pulser frequency, the envelopes don't retrigger everytime. I have to raise the Pulser frequency (slower) to get the envelope to retrigger.
I'm assuming this is normal, since the sustain (duration) phase is too long to receive a new trigger with fast Pulser frequencies?
However, the other way aroudn the duration-slider also seems to influence/stop the Pulser when it's in high frequency (Pulser led light goes dim).

So in short: with only two cards (3 & 4), is the EG supposed to influence the Pulser this way?
Or is it impossible to tell for sure with only these two cards hooked up?

I should add I didn't wire any of the banana jacks to the motherboard yet.
I also measured the 13.5V spot on card 3 and got 13.42V there so I'm guessing that's within range?

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Re: 208p build thread (papz's PCBs)

Post by papz » Mon Jan 13, 2020 7:41 am

The EG settings shouldn't influence the pulser behaviour.
13.42V is ok.
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Re: 208p build thread (papz's PCBs)

Post by jasonjasonson » Mon Jan 13, 2020 7:50 am

papz wrote:
Mon Jan 13, 2020 7:41 am
The EG settings shouldn't influence the pulser behaviour.
13.42V is ok.
Hi Papz, thanks for the reply!
So should I be able to troubleshoot this with only these two cards? Or should card 12 (output) also be up?

My cards are pretty neatly soldered and flux-cleaned, so I might try swapping some IC's?

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Re: 208p build thread (papz's PCBs)

Post by papz » Mon Jan 13, 2020 3:51 pm

When i build a 208, I test all at once when finished, I'm not fan of partial testing.
Card 12 is needed to connect Q and N grounds, likely those are already connected on your PSU since it works without it.
The pulser and EG should work without other cards. There are various possible causes to your issue : short on the MB, faulty IC...
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Re: 208p build thread (papz's PCBs)

Post by Dimitree » Mon Jan 27, 2020 9:27 am

does anyone knows if I can use 100K slide pots instead of 50K? I have a bunch of them and they fit.
I guess it won't make any difference but maybe I need to change the values of the two resistors aronud each potentiometer. What do you think?
thank you

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Re: 208p build thread (papz's PCBs)

Post by papz » Mon Jan 27, 2020 9:55 am

Are voltage dividers so it shouldn't be an issue.
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Re: 208p build thread (papz's PCBs)

Post by Dimitree » Mon Jan 27, 2020 11:04 am

thank you,
do you think I should adapt the 120K resistors on the slide pots to reflect the change? I guess the taper will be changed when I move from 50K to 100K sliders

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Re: 208p build thread (papz's PCBs)

Post by papz » Mon Jan 27, 2020 11:13 am

I don't think so.
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Re: 208p build thread (papz's PCBs)

Post by Chaotic » Sat Feb 15, 2020 5:47 pm

Solving the bleeding when the main output pot is in ccw.
Earlier I minimized some of the bleeding through the main with a wire from the distro card to the Q ground beside the card #12. Page 22 in this thread.
I have lived with it for a while but was not satisfied. Especially in silent parts when I´m doing gigs.
Thinking about it and its quite strange that when the pot is fully ccw should the signal from the pot be zero. Ccw on the pot is tied to Q ground and that seems not to be enough ground. Strange, because the Q and N ground is tied together on the card #12. Maybe minimal voltage difference through the tracks and card connectors have to do something with it? On mine 208
Tried with a link between the ground wire from distro board to ccw on the pot.
The thick black wire is direct ground from the distro board.
YES, now the is the 208 totally quiet when the main is at zero. :banana:
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Re: 208p build thread (papz's PCBs)

Post by Llewspeed » Sun Feb 16, 2020 6:00 pm

Hi to all builders, I’m troubleshooting my 208 and everything seems to be ok except modulation oscillator. It completely silent. I have changed all IC’s. I also tried to swap ua726 (replacement pcb) with 2n3904 pair - no sound. I also tried to swap LS312 with 2n3906 pair - no sound. The only parts which I didn’t change are 3565 and 4341 transistors.
BTW, RC4136 becomes quite hot even after replacement with new one.

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Re: 208p build thread (papz's PCBs)

Post by PacificState » Mon Feb 17, 2020 4:28 am

Is it modulating the complex oscillator, even if you can't route it directly to the output? I had that problem initially, but found (by following the schematics) that I'd missed out a resistor from the board - luckily right near the edge, as I'd already put the panel on. A scope will be helpful - you can probe the card pins for the MO signal.

Otherwise, RC4136 getting hot does sound a little odd - have you checked all your soldering for shorts?

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Re: 208p build thread (papz's PCBs)

Post by Llewspeed » Tue Feb 18, 2020 3:49 pm

PacificState wrote:
Mon Feb 17, 2020 4:28 am
Is it modulating the complex oscillator, even if you can't route it directly to the output?
Yes, it modulates complex oscillator. I checked for shorts for 10 times - no shorts.

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Re: 208p build thread (papz's PCBs)

Post by PacificState » Tue Feb 18, 2020 4:59 pm

Download the schematics and follow the signal path through - that’s how I found I’d left off the last of the 120k resistors (R84) from the motherboard.

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Re: 208p build thread (papz's PCBs)

Post by papz » Wed Feb 19, 2020 5:42 am

If the MO modulates the CO properly, the problem may also be in LPG2 or output channel B. Can your hear the CO on output ch B with the routing switch to bottom, ie LPG2 in series with LPG1 with phase shift ? If no, the fault is in LPG2 (card 11) or output channel (card 12), or a missing / wrong value / misplaced resistor on the MB indeed.

If the new 3146 gets hot and the former one doesn't, it may be faulty, replace it.
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Re: 208p build thread (papz's PCBs)

Post by Llewspeed » Wed Feb 19, 2020 3:33 pm

papz wrote:
Wed Feb 19, 2020 5:42 am
If the MO modulates the CO properly, the problem may also be in LPG2 or output channel B. Can your hear the CO on output ch B with the routing switch to bottom, ie LPG2 in series with LPG1 with phase shift ? If no, the fault is in LPG2 (card 11) or output channel (card 12), or a missing / wrong value / misplaced resistor on the MB indeed.

If the new 3146 gets hot and the former one doesn't, it may be faulty, replace it.
New 4136 remains hot but I can keep a finger on it.
MO modulates CO not properly and only on FM mode.
LPG2 works with the external signal.
I can’t find any waveform from card 6. I also know that ua726 pcb works properly.
I made a short video to see a modulation behavior.

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Re: 208p build thread (papz's PCBs)

Post by papz » Thu Feb 20, 2020 4:18 am

LPG2 and output ch B seem ok.
It's not clear on the video how MO modulates CO, or doesn't, but it seems to affect the CO frequency. No waveform and the hot 4136 on board 6 suggest there's an issue on this board but where did you monitor the waveform ? Signal should be present on pins 4 and 11 of the Molex header.
The modulation is managed on board 5, which can be a PITA to set up properly, check Dave Brown's notes about it, very helpful.
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Re: 208p build thread (papz's PCBs)

Post by Karma » Mon Feb 24, 2020 4:49 pm

Llewspeed wrote:
Wed Feb 19, 2020 3:33 pm
papz wrote:
Wed Feb 19, 2020 5:42 am
If the MO modulates the CO properly, the problem may also be in LPG2 or output channel B. Can your hear the CO on output ch B with the routing switch to bottom, ie LPG2 in series with LPG1 with phase shift ? If no, the fault is in LPG2 (card 11) or output channel (card 12), or a missing / wrong value / misplaced resistor on the MB indeed.

If the new 3146 gets hot and the former one doesn't, it may be faulty, replace it.
New 4136 remains hot but I can keep a finger on it.
MO modulates CO not properly and only on FM mode.
LPG2 works with the external signal.
I can’t find any waveform from card 6. I also know that ua726 pcb works properly.
I made a short video to see a modulation behavior.
I have the same issue, no sound, slow modulation with the complex osc, no waveform anyware on scope, and the 4136 are hot too, i changed them and the 2N3565, but nothing move. I think it's probably 2n4339 or the 2n4341, for the moment i don't have anytime to test them, have you bought your rare component from SAmodular? perhaps a bad batch from some of them :despair:

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Re: 208p build thread (papz's PCBs)

Post by Llewspeed » Tue Feb 25, 2020 3:54 pm

Karma wrote:
Mon Feb 24, 2020 4:49 pm
I have the same issue, no sound, slow modulation with the complex osc, no waveform anyware on scope, and the 4136 are hot too, i changed them and the 2N3565, but nothing move. I think it's probably 2n4339 or the 2n4341, for the moment i don't have anytime to test them, have you bought your rare component from SAmodular? perhaps a bad batch from some of them :despair:
I finally solved it! Wrong pn3565 direction was the issue. They have wrong direction on card 6 drawing, top pin is collector.
Thank you guys for your help.

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Re: 208p build thread (papz's PCBs)

Post by papz » Tue Feb 25, 2020 4:04 pm

:tu:
If PN3565 are used instead of 2N3565 they should be mounted "upside down" with the rounded side pointing to the outside indeed.
It is mentioned on viewtopic.php?p=2753788#p2753788 but I'll add this to the build notes.
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Re: 208p build thread (papz's PCBs)

Post by Llewspeed » Tue Feb 25, 2020 5:09 pm

papz wrote:
Tue Feb 25, 2020 4:04 pm
:tu:
If PN3565 are used instead of 2N3565 they should be mounted "upside down" with the rounded side pointing to the outside indeed.
It is mentioned on viewtopic.php?p=2753788#p2753788 but I'll add this to the build notes.
Thanks, Papz! You shoul add it, because I couldn’t imagine they have different pinout.

Excuse me for editing, I found info about the tank, thank you.
Last edited by Llewspeed on Tue Feb 25, 2020 5:21 pm, edited 2 times in total.

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Re: 208p build thread (papz's PCBs)

Post by papz » Tue Feb 25, 2020 5:20 pm

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.

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Re: 208p build thread (papz's PCBs)

Post by heapish » Sun Mar 15, 2020 5:43 pm

Hey,
Just done a quick read of all the posts and made a few notes for before I order parts (yea im waaaay behind)
The only thing I've not got my brain round is the Vactrols. How should I go about selecting them? And how is best to match the ones on boards 10 and 11?
Your build notes say a Dual VTL5C3/2 will do the job but the FAQ says someone reported that it messed with the LPG behaviour.
Cheers :party:

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Re: 208p build thread (papz's PCBs)

Post by papz » Sun Mar 15, 2020 7:23 pm

I select vactrols on test in the actual circuit they will be used in, but this requires to have some quantities.
To measure and match them, please refer to Dave Brown's how to on viewtopic.php?f=17&t=193690&p=2717652

The VTL5C3/2 dual vactrols reported bad for the LPGs are Xvive ones only. I use Excelitas VTL5C3/2 in my builds without any problem.
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.

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