208p build thread (papz's PCBs)

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

Post by papz » Fri May 15, 2020 5:37 am

The Edac are green, this looks awful on a 208.
The Amphenol 225-22821-101 are super nice but may be hard to find and expensive.
LW-N28A2G on ebay are good and cheap, used on my expansion cards and ok for 208 too.
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Re: 208p build thread (papz's PCBs)

Post by Peti » Fri May 15, 2020 6:41 am

there are some amphenol on the US, with a lot of shipping but not so expensive. but in total more expensive than going this way:

https://www.samodular.com/product/lw-n28a2g-connector/

i might just go with that one :)

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

Post by search64 » Fri May 15, 2020 9:38 am

If you do a groupbuy, the Amphenol's are really nice. They're a lot heavier and sturdier, and I believe it's what the originals use. I got a pair through a groupbuy a year or so ago.

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

Post by AlanP » Fri May 15, 2020 3:36 pm

Should I solder the 9mm pots straight down on the PCB? Not all of the shaft sticks through the panel, and none of the threading.

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

Post by papz » Fri May 15, 2020 3:41 pm

Yes
You can leave the nut on the thread and tighten it behind the panel.
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Re: 208p build thread (papz's PCBs)

Post by Peti » Thu May 21, 2020 6:39 am

again a BOM related question, toggle switches:

as they are really expensive on mouser i found them on TAYDA, but not sure if they are 100% suitable, the SPDT ON-OFF-ON for example:
https://www.taydaelectronics.com/mini-t ... ff-on.html

they are 1M Series, compared those on the BOM are 7000 Series, is that an issue?

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

Post by papz » Thu May 21, 2020 7:25 am

again a question answered in the FAQ :
http://www.portabellabz.be/208pcbfaq.html#parts wrote:Is there an alternative to the expensive C&K switches listed in the BOM ?
Taiway switches available from Small Bear are very nice and cheaper.
Any toggle switch can be used for the SPST on-off and on-off-on ones, but I don't recommend to use cheap ones, replacing a faulty switch ain't no fun.
For the DPDT on-on-on switches use Small Bear's Taiway or the BOM's C&K ones only, other ones might have a different pinout and not work on this PCB.
The PCB fits both PCB mount (with thin lugs) and panel mount (with larger lugs) switches.
:hihi:
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Re: 208p build thread (papz's PCBs)

Post by Peti » Thu May 21, 2020 8:05 am

:doh: oh i did not see that coming!
sorry

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

Post by jonen » Wed May 27, 2020 9:44 am

Unfortunately, my modulation oscillator stopped working. I am using the pa726 boards and for some reason the voltage regulator on it burned through, not really sure why, maybe a shortage accidentally caused by me.

I have since replaced the voltage regulator and confirmed the pa726 to be working by testing it in the complex oscillator. I also replaced all ICs on card 6, however there is still no sound, and IC2 (RC4136) gets really hot. Now I suspect that one of the transistors needs replacing, but I am not sure which. I took some voltage measurements, assuming they are all dc, I am not sure if this is true. Would there be any chance for anyone to verify these? I would greatly appreciate it, since those transistors are quite difficult to source.

Image

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

Post by papz » Wed May 27, 2020 9:49 am

I'd rather desolder each transistor and test it to get more reliable results.
A cheap tester like this is good to have and enough to spot faulty ones : https://www.befr.ebay.be/itm/Transistor ... 3431627171
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Re: 208p build thread (papz's PCBs)

Post by jonen » Thu May 28, 2020 6:50 am

Thanks for the tip! I ordered one!

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

Post by tele_player » Thu Jun 04, 2020 11:25 am

I just found that Hammond 1773 needs some modification to hold the 208p. I’d appreciate any advice from somebody who has done this.

I’m just a few parts away from first power up. Exciting!

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

Post by HipDestroyer » Fri Jun 05, 2020 2:47 pm

Hello everyone

I am building a 208 and have run into some trouble with the Timbre (card 9) part of it.

Symptoms:
Waveshape selector (SW17) and Waveshape control (POT17) have no effect on the output signals, but the timbre offset contol slider does.

My first suspicion was the DG200BA. I checked it with a scope and saw the following:

Measuring with scope:
- "spike" signal on In1
- Smaller spike sig on S1
- on D1 is the folded wave affected by the timbre offset control slider

- square on In2
- On S2 I see a squary chopped sine with spikes, rising and falling depending on the timbre offset control slider
- On D2 I see a squary sine with spikes, rising and falling depending on the timbre offset control slider

So I guess the DG200BA is fine?

The waveshape control potentiometer is (POT17) b100k has 13.5V at pin1, 0-13.5V at pin2 so that seems fine.

Then my next suspicion is the MCP846. But I have no idea how to test them. Can anyone give me some pointers?

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

Post by papz » Fri Jun 05, 2020 3:26 pm

Try and swap the ICs on card 8, IC2 being the first suspect.
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Re: 208p build thread (papz's PCBs)

Post by HipDestroyer » Fri Jun 05, 2020 3:42 pm

papz wrote:
Fri Jun 05, 2020 3:26 pm
Try and swap the ICs on card 8, IC2 being the first suspect.
Thanks for the suggestion. Just tried this and it didn't work

From 4016BE to 4066BE --> Did not make a difference
From 4066BE to different 4016BE --> Did not make a difference

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

Post by papz » Fri Jun 05, 2020 3:44 pm

Swap the other ones and check the vactrol is not mounted upside down.
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 HipDestroyer » Fri Jun 05, 2020 4:11 pm

papz wrote:
Fri Jun 05, 2020 3:44 pm
Swap the other ones and check the vactrol is not mounted upside down.
YES!!! This was exactly it. Vactrol on card 8 wrongly oriented. Thanks!!!!!!!

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

Post by papz » Fri Jun 05, 2020 4:15 pm

Happened to me too, cheers !
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 AlanP » Fri Jun 12, 2020 4:42 pm

Anyone know of a source for 1BC2E tanks that are not in Germany? The German couriers are being very grumpy about shipping to New Zealand.

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

Post by captnapalm » Fri Jun 12, 2020 8:57 pm

AlanP wrote:
Fri Jun 12, 2020 4:42 pm
Anyone know of a source for 1BC2E tanks that are not in Germany? The German couriers are being very grumpy about shipping to New Zealand.
you can get them directly from the manufacturer in Korea.

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

Post by tele_player » Sat Jun 13, 2020 8:00 pm

Just powered up my 208p build for the first time. Completely uncalibrated, and using transistors (2N3904) before installing the pa726 boards, but so far, everything seems to work. Only thing I noticed was that sequencer wouldn’t do 4 steps. 3 and 5 were OK.

Update: after a few hours, I decided to pull card 1 and investigate sequencer. Saw no obvious problem on card. Put it back, powered up, was fine for a while, then random stopped working on a couple of white bananas, but not all. Then pulser stopped. Now almost nothing works.

Maybe wrestling the card in and out caused a problem? Jostled a bad connection?

Power supply is mini distro board, powered by meanwell RT-65C. Voltages and LEDs at distro board still correct.

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

Post by papz » Sun Jun 14, 2020 5:21 am

Sounds like a major problem, I never saw this kind of "chain reaction".
I'd start by checking the power rails on the motherboard with no card and add them one by one starting with card 12 (Q and N short) and card 3 (13.5V which controls all parameters).
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 tele_player » Sun Jun 14, 2020 11:15 am

That's exactly what I planned.
Adding cards back in , observed that card 2 (random voltage) made everything stop working. Removed all ICs on card 2, and pulser, sequencer started working again. Reinstalled card 2 chips one by one, isolated trouble to IC2.
I'm using 4066 for 4016 locations, I replaced IC2 with a new 4066, everything started working again.

Reinstalled remaining cards one by one, no problem. All cards in : wonderful 208 sound!

So, for now, things look good, except,
Sequencer still not correct. Select switch 3 or 4 gives 3 stages, select switch 5 gives 4 stages. This is different from yesterday, so I still need to examine Card 1. Maybe this needs decoupling caps as Dave Brown suggests?

Right now, I am SO relieved.

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

Post by fg » Sun Jun 14, 2020 11:29 am

"decoupling" this is the solution that worked for me!

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

Post by tele_player » Sun Jun 14, 2020 11:37 am

fg wrote:
Sun Jun 14, 2020 11:29 am
"decoupling" this is the solution that worked for me!
Did yours have similar symptoms?

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