208p build thread (papz's PCBs)

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Peti
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Re:

Post by Peti » Thu Apr 16, 2020 8:54 am

cormallen wrote:
Mon Dec 17, 2018 4:02 am
All sorted on the sine wave shaper: it was indeed an out-of-spec 2N4339 in Q1. I tried a selection of different J201's until I found one that worked perfectly.

For the LPGs, I matched both pairs of vactrols for resistance across their LED input voltage range, but didn't pay any attention to the response speed. I've noticed that LPG2 is a lot snappier than LPG1, and I think I prefer that sound. Is there a good way to measure speed of vactrols? Just hit it with a pulse and time it on the scope?

Is it worth buying a bunch more vactrols, just on the off chance that I can find another matched pair that is also snappy? How many would I have to buy to have a decent chance of finding such a pair? (Out of my original set of 15 vactrols, I only found two closely matched pairs anyway!)

Thanks.

So it is possible to just use an J201 Transistor for Q1 instead of the more expensive 2N4339? or did you put the J201 additionally? :)

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

Post by tele_player » Thu Apr 16, 2020 10:03 am

I’ve started my 208p project, boards/panel due in a few days, other parts in next few weeks.
Ultimately, I plan to assemble a 218, but meanwhile, how to trigger the 208?

Has anybody devised a simple diy to use a Keystep CV + gate to drive the 208?

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

Post by papz » Thu Apr 16, 2020 10:14 am

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 » Thu Apr 16, 2020 11:43 am

Thanks, I was hoping for something else so I could avoid looking at that website.

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

Post by papz » Thu Apr 16, 2020 11:50 am

Don't you like my website ? :mrgreen:
Last edited by papz on Thu Apr 16, 2020 11:55 am, edited 2 times 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.

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

Post by tele_player » Thu Apr 16, 2020 11:53 am

papz wrote:
Thu Apr 16, 2020 11:50 am
Don't you like my website ? :mrgreen:
I like your website much more than Synovotron. I apologize for the confusion.

Question, is the 208 very critical about the 10v pulse? Would 9v satisfy its demands?

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

Post by papz » Thu Apr 16, 2020 11:58 am

:lol:
9V should work.
The GTPulse is a great addition.
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: Re:

Post by cormallen » Thu Apr 16, 2020 3:14 pm

Peti wrote:
Thu Apr 16, 2020 8:54 am
So it is possible to just use an J201 Transistor for Q1 instead of the more expensive 2N4339? or did you put the J201 additionally? :)
It worked fine for me!

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

Post by Peti » Thu Apr 16, 2020 3:47 pm

ok :-)
thank you !

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

Post by papz » Sat Apr 18, 2020 11:25 am

papz wrote:
Tue Apr 14, 2020 6:55 am
A 208 built with Xvive VTL5C3/2 on boards 10 and 11 will arrive on my bench soon for servicing, I'll chek the LPG behaviour and compare with the Excelitas VTL5C3/2 that I use in my builds (no, I don't have any for sale, sorry :foul: ).
There was almost no difference between LPF and combination modes with the Xvive VTL5C3/2. Replacing those with Excelitas VTL5C3/2 fixed the problem. This confirms the Xvive VTL5C3/2 were well in cause.
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 search64 » Sat Apr 18, 2020 11:41 am

Great, thanks for that followup. Now to find some Excelitas...

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

Post by papz » Sat Apr 18, 2020 1:36 pm

I'm curious if a pair of selected on test Xvive VTL5C3 would work...
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 search64 » Sat Apr 18, 2020 2:09 pm

I think the variance on those is quite big so I expect so.

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

Post by Peti » Mon Apr 20, 2020 3:04 am

Hi everyone, :cloud:
i found a website where you can make inquiries for certain rare parts: https://www.digipart.com/part/VTL5C3%2F2
lets see how expensive this is

in this case i was looking for Excelitas VTL5C3/2 ;)

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

Post by tele_player » Mon Apr 20, 2020 8:45 am

That's interesting.

Did you find any Excelitas VTL5C3/2 for sale?

Update: my 208P boards just arrived. Very nice - exciting!

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

Post by tele_player » Tue Apr 21, 2020 8:18 am

Most parts are here, or on their way. Haven't found these two yet:

LM301 - only ones I've found are on eBay. Some are likely counterfeit (wrong number of pins), some have crazy shipping (e.g. $4 chip, $20 shipping), a few look like clean pulls from socketed devices... What to do?

edit: I ordered what appear to be clean pulls from eBay, at a reasonable price. I'll test them when they get here. But a simple voltage follower test won't catch sneaky relabeled counterfeits. The perils of recreating a design from nearly 50 years ago.

Reverb tank - I haven't found this part anywhere in USA, and haven't found an enclosed 8" model to cannibalize anywhere, either. Samodular lists it, but it's out of stock. I might not be able to avoid another crazy shipping fee.

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

Post by Peti » Tue Apr 21, 2020 9:04 am

Yes, the first one, Classic Components Corp. has them. you have to fill out your data first, then send an inquiry, they cost 20dollars/piece.

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

Post by tele_player » Tue Apr 21, 2020 11:53 am

Wow. This must be a magic op amp!

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

Post by tele_player » Tue Apr 21, 2020 1:14 pm

For LM 301, has anybody here tried LM201 SMD chip in a DIP adapter?

That would cost under $1 each.

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

Post by search64 » Tue Apr 21, 2020 3:45 pm

LM301 is not special at all, just obsolete.

You can still get them from Farnell for instance for about 60 cents: https://uk.farnell.com/texas-instrument ... B-OCTOPART

There’s an SMD version on Mouser:
https://eu.mouser.com/ProductDetail/ON- ... 52BV4TM%3D

Oh and I got my reverb here:
https://www.tonefactory.nl/accutronics-reverb-can-1bc2e

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

Post by tele_player » Tue Apr 21, 2020 7:13 pm

That Farnell link didn’t show any LM301 available. Yes, I’m considering using SMT with an adapter.

Here in USA, LM301 and that reverb aren’t found anywhere. Having already spent a lot on shipping from portabellbz and samodular, I was hoping for USA sources.

But I will keep those in mind.

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

Post by search64 » Tue Apr 21, 2020 11:56 pm

Synthcube has LM301: https://synthcube.com/cart/lm301an-nopb ... arch=Lm301

Banzai music has the reverb: https://www.banzaimusic.com/accutronics-1bc2e.html

Could have gotten the reverb from samodular as well.

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

Post by tele_player » Wed Apr 22, 2020 12:58 am

Thanks, I’ll use synthcube and banzai.

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

Post by Peti » Fri Apr 24, 2020 4:56 am

I found cheaper Excelitas Vactrols, for all who are interested in that. a chinese company storing rare parts https://www.depu.hk.cn
i ordered a lot Excelitas VTL 5C3 (single) for 2 dollars a Vactrol which is really cheap!

@papz: concerning Card 5, is the hand selecting of Vactrols also necessary if i use Excelitas for the 7 VTL slots?
and if yes, can the Dave Brown Card 5 modification be done exactly the same way as for the 208r? (roman clone)


"Cut the runs on the back of the PCB to IC4 pins 8 and 9 and jumper the run going to pin 8 over to pin 9, remove R23, add a 15K resistor from pin 10 to pin 8 and add a resistor from pin 8 to ground to set the proper gain (I've used values between 5K and 10K)."

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

Post by papz » 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 ?
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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