208p build thread (papz's PCBs)

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

Post by Peti » Sun Apr 26, 2020 3:20 am

Hi,
ok then i will use sockets for VTL 1 2 3 4 on board 5. then i will see if i need it : )
thank you!

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

Post by tronotape » Sun May 03, 2020 10:14 pm

EDIT: Solved. IC 2 was fried sending a huge offset into the reverb input that fried the first tank.

Reverb issue.

I’m getting a reading of +14.3v on the outside leg of the reverb pot. The issues is definitely on card 12 as the voltage is not there when the card is disconnected. It appears to have already fried one tank so I’m hesitant to test my new one.

My question would be; what is the voltage present at IC 1 pin 4 when no tank is connected and is it normal that it would be to the positive rail?
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Re: 208p build thread (papz's PCBs)

Post by papz » Mon May 04, 2020 1:31 pm

14.3V with no tank connected on IC1 pin 4 and on the reverb pot is normal, I just checked in a 208 I'm working on.
Most reverb issues are caused by a dead tank. Always the same problem : broken output coil, they are very very very fragile and can break during the module manipulation even if the tank is left untouched, I have a large (but useless) collection of dead 1BCDE tanks, all with the exact same coil issue.
You can measure the coils resistance : input should be about 25 ohms, output about 900 ohms. Infinite resistance means the coil is broken and the tank needs replacement.
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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 xahdrez » Thu May 07, 2020 2:33 pm

papz wrote:
Fri Apr 24, 2020 6:05 am
Yes you need to select vactrols 1 2 3 4 on board 5, or to be very lucky.
Yes Dave Brown's mod is recommended most of the time, its purpose is to reduce the AM amplitude differences, but in some builds it was not needed.

I'm curious if these vactrols from China are really Excelitas... Did they send you pics ?
I've taken chances on one of these (had one original Excelitas VTL5C3/2 knocking about which sounds great on LPG, and one xvive which does not sound as good - hoping to swap it out if this pans out):

https://www.ebay.co.uk/itm/NEW-VTL5C3-2 ... 2749.l2649

Picture on the listing is the wrong one, but they did send another through message which seemed to look legit (i.e. actually a VTL5C3/2, not xvive). Not an endorsement at all at this stage, and could be an expensive mistake - but will report back in 2-4 weeks....
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Re: 208p build thread (papz's PCBs)

Post by papz » Thu May 07, 2020 3:58 pm

https://endorphin.es/assets/endorphin.e ... cedure.pdf explains well how to roll your own vactrols.
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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 Peti » Sat May 09, 2020 3:49 pm

nice! did you try to construct a vactrol on your own yet ? :)

i just received "fake" single ones (2$) from the chinese website; the dual 5C3/2 (14$) seem to be real Excelitas

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

Post by papz » Sat May 09, 2020 4:03 pm

Not yet.
There are threads about doing vactrols in the DIY section, someone also shared 3d printer files to make cases, you can do a search fore more infos.

Nice find on the Excelitas VTL5C3/2, I asked them for a quote but got no reply.
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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 May 10, 2020 12:42 am

papz wrote:
Thu May 07, 2020 3:58 pm
https://endorphin.es/assets/endorphin.e ... cedure.pdf explains well how to roll your own vactrols.
The 208 already seems rather picky about vactrols - do you think it is likely that people will DIY better?

I’ve just started building a 208p, and I’m dreading the vactrol stuff.

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

Post by Peti » Sun May 10, 2020 4:01 am

papz wrote:
Sat May 09, 2020 4:03 pm
Not yet.
There are threads about doing vactrols in the DIY section, someone also shared 3d printer files to make cases, you can do a search fore more infos.

Nice find on the Excelitas VTL5C3/2, I asked them for a quote but got no reply.
they were very friendly in my case, even given us the money back because the single were not Perkin Elmer.
I ordered them from Depu Electronics - phoenix@depu.hk.cn

there is also March-Technology, they quote 11$ per Vactrol when you take 100 pieces - athena@march-tech.com
19$ when you take single.
so i bought the ones from phoenix but we did not test them yet. i don't hope for bad surprises.. :eek:

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

Post by papz » Sun May 10, 2020 5:50 am

Rolling your own vactrols is the best way to be very picky without paying insane price.
For the price of a vactrol you can get a lot of LEDs and photoresistors and experiment with to find the perfect response you want by selection on test.

All pre-built vactrols such as Excelitas, Xvive, Perkin-Elmer, Vactec... are nothing more than a LED and a photoresistor in a sealed case. Selection on test is requested as well with those because of their huge tolerance, the specifications and behaviour vary a lot even in a same batch of the same manufacturer.
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Re: 208p build thread (papz's PCBs)

Post by tele_player » Sun May 10, 2020 9:21 am

I totally agree, the parts are very cheap. But to use them practically, it would be very useful to produce a microcontroller based system to test and match the DIY vactrols. Conceptually, this is not a difficult problem.

Or, somebody could buy Xvive parts in large quantities, and test and grade them for the parameters which are important for synth use. The best person for this would be Xvive, they could sell the rejects for use in less demanding applications.

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

Post by papz » Sun May 10, 2020 9:32 am

This is not specific to the 208p build, please discuss this in another thread.
You may find this one about Xvive's vactrols and their care of customers' remarks interesting : viewtopic.php?f=17&t=222441
Thanks
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Re: 208p build thread (papz's PCBs)

Post by Peti » Tue May 12, 2020 10:10 am

which value for the 8 potentiometers is used originally, and recommended for the 208p? Bom says 10k-100k for the 9mm and for the 16mm

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

Post by papz » Tue May 12, 2020 10:17 am

Any value between 10k and 100k is ok. I generally use 50k.
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.
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Re: 208p build thread (papz's PCBs)

Post by Peti » Tue May 12, 2020 10:40 am

ok thank you!.
and another thing you did not note in your build notes, you say that using sockets for all IC's is recommended.

in the EMS build notes they say for Card 12: "Solder IC2, IC3, IC4 directly to a PCB, do not use an IC-socket - this is required for a better cooling of these amplifiers."
is this true for the 208p?

and furthermore all the other notes quoted on this EMS 208 specific website should be applied as well on your pcb? :)
https://electricmusicstore.com/blogs/bu ... -model-208

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

Post by papz » Tue May 12, 2020 10:44 am

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

Post by Peti » Tue May 12, 2020 11:02 am

then the LM380 better work :D removing IC's not funny

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

Post by papz » Tue May 12, 2020 11:13 am

You can also socket them with heatsinks pasted on top.
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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 Peti » Tue May 12, 2020 1:03 pm

OK. i might try that to be safe, if i find some that are suitable!

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

Post by search64 » Tue May 12, 2020 1:29 pm

I used these, they slide onto the IC. No pasting necessary.

https://nl.mouser.com/ProductDetail/aav ... cycode=EUR

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

Post by Peti » Tue May 12, 2020 4:39 pm

great, thanks for the tip!

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

Post by tele_player » Thu May 14, 2020 2:51 pm

I've read this thread, and only found one answer to this question, and it's not very clear:

I've got the JAMMA 56 pin connectors included in the SAMODULAR parts kit, and I've cut off the tabs on one as suggested on Dave Brown's site. My question - should I install the one with the tabs on the main board, without modification?

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

Post by papz » Thu May 14, 2020 3:00 pm

No, the tabs would upset the transfer card placement and likely the contacts soldering.
Cut all the tabs flush.
I don't understand why SAmodular sells edge connectors with tabs, this is not the right type for this build.

The edge connectors should be mounted against the panel and MB like this :
101_0204.resized.JPG
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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 » Thu May 14, 2020 3:43 pm

Perfect - very clear to me now, thanks!

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

Post by Peti » Fri May 15, 2020 5:28 am

@papz: which ones do you recommend (EDAC 56 pin) if not the Samodular? :)

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