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VCS3 Card for 208 and Easel build thread
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author VCS3 Card for 208 and Easel build thread
papz
The PCBs are available on http://www.portabellabz.be/vcs3.html

BOM : http://www.portabellabz.be/images/vcs3/VCS3_Card_tr_BOM.xlsx
Build notes : http://www.portabellabz.be/images/vcs3/VCS3_Card_build_notes.pdf - Please use the latest revision, the date is on the last page.
Users manual : http://www.portabellabz.be/images/vcs3/VCS3_Card.pdf
Dave Brown's page : https://modularsynthesis.com/roman/VCS3/vcs3.htm

jonny_w
Awesome! Any plans on offering a black version to match my Toolbox, BOB, and Easel set? Blue is fine of course, but I had to ask Mr. Green
papz
Thanks
No plan on a black version, sorry.
pathein
have just ordered the pcb and looking around for the non tayda parts,

for the metal can NPN supermatched pair(2N2916 or MAT02 or LM394 or KC811)

most are hard to get from where i am and worried bout fake old parts of sort. Then i saw cabintech has the as194H/394H (194H)

Hi papz, was wondering for this part, will it be critical together with the 1k tempco, as in using the 194H instead of 394H.
papz
Thanks for your order, I posted it today.

I haven't tested this 194H but it should work, in fact any metal can NPN supermatched pair should be ok, or even 2 matched NPN transistors glued together, as it was in the early Synthi A and VCS3 (but this may reduce tracking accuracy and stability).

I just tested cheap MAT02EH purchased on ebay (seller adeleparts2010), probably are fakes because the labeling is different and their hFE is much lower than real ones that I have (the Chinese one is 171, the real one 662) but the pinout is ok, the pair is properly matched and I could get a perfect tracking over 5 octaves.
heapish
Jaw on the floor we're not worthy
pathein
Thanks Papz, for the pcb and info on the transistors!
papz
You're welcome, happy building !

I just modified the card edge connector of Jerome's 208r rev1 to fit in the VCS3 Card and it works perfect.
I'll post the modification details on my website soon.
papz
I updated the build notes with
208r rev1 program card slot modification
CO dedicated output modification (the CO is a great master for the VCS3 Card oscillator sync input)
papz
I updated the build notes with some helpful info.
Happy building.
papz
Still no questions despite 15 DIY PCB sets were sold ?
Hopefully this means no builder had problems. thumbs up

In a batch of KC811 with code A50 and A40, many cause small jumps in the oscillator pitch, mostly noticeable in high frequencies, and others are ok.
These supermatched pairs are cheap and good working when ok but need selection on test, it may be better to buy another type if you plan to buy only one.

I ordered some AS394 from https://www.ericasynths.lv/shop/diy/diy-accessories/as394-matched-tran sistors/ and will test in a few days.
jonny_w
Guess I'll be the first Mr. Green

I'm getting no output on anything, no LED indication from the card. Here are some findings:

LM7812 output: +12.2V
LM7909 output: -9V

All TL072 cards are showing a Vcc of +14.3V/-14.4V

Pictures:



papz
The measured voltages are ok. The TL072s are powered separately.
No noise or random output is normal as long as the SOT 2N5172 is not in place.

Check all solder joints for bad solder or bridges (I seem to see one between the top lead of the BC214L located between the 2 shape resistors and the 330pF cap located above it) and clean the flux.

Check all transistors are the right type and there's no 2N5172 in place of a BC214L or vice versa.

Are you sure of the LM394 provenance, is not a fake ? Did you test it ?
jonny_w
Good eye! It *was* a solder bridge at the BC214L. Fixed it and now it's come to life. Thanks! thumbs up
papz
SlayerBadger!
jonny_w
After calibrating, it seems everything works except for my random.

The mini slide switch is toggled down, and I'm not getting random CV output. Any suggestions on what to check?
papz
Do you clock the random via the 208's inverter "to prog" socket ?
jonny_w
papz wrote:
Do you clock the random via the 208's inverter "to prog" socket ?


I was plugged into the "from prog" socket d'oh!

All good now! I love this thing. Such a great compliment to the Toolbox & 208 thumbs up
papz
So do I w00t
Thanks for the feedback !
papz
papz wrote:
I ordered some AS394 from https://www.ericasynths.lv/shop/diy/diy-accessories/as394-matched-tran sistors/ and will test in a few days.


I finally tested one, sorry for the delay. oops
It works very good, I'll recommend it in the BOM. thumbs up
eveready9v
So in the calibration manual it says:
"Allow about 10 minutes warm up for better stability.
With the "frequency" and "fine" panel pots at mid-course, adjust the "frequency" trimpot to get about 100Hz."
Do I do this with the switch set to Hi or Low? I'd imagine its Low but I just wanted to double check.
Thanks
Barry
papz
The tracking should be calibrated with the switch set to hi position.
Thanks for pointing this, I added this info to the calibration procedure.
davebr
I just built one of these for a client. I posted photos and scope images on my Portabellabz VCS3 Card page.

Dave
papz
Thank you Dave thumbs up
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