**** FORMANT VCO PCB ****

[jbv]

Hi VC-folks,

Here we go (after delays due to some unsolved e-mail problems). 
I tried several times to post the files relative to the new
Eurocard PCB design for the FORMANT VCO, but nothing came through.

Fortunately, Josh Brandt offered to post it on his web site.
He is currently decoding it, and it should be available on
April 30 at http://www.ultranet.com/~mute, under "synthesizers".

The stuff consists in 3 gif files relative to the new Eurocard
design for the Formant VCO :

        - PCB : PCB design
        - LAYOUT : PCB + components
        - LIST : components list (modif. of book #2 included)

This PCB is single side. As you will see, the layout is dense, 
but not too much. I could have gained some extra space by 
putting all Rs vertically, but I hate to do that.
I also did my best to include as few straps as possible 
(don't forget those around ic11, ic9 & ic8 !), and to make trim
pots easy to access for calibration once the card is in its box.

The dashed lines on the LAYOUT file have nothing to do with
components or straps : they only give indications about voltage and
switches / pots connections.

My modification concerns P3 & R5, which I have duplicated as
P3a/R5a and P3b/R5b. R5a & R5b are both connected to pin 2 of
IC4 (please refer to the original schematic). This provides an
extra FM input.

Some of you suggested a layout with "a heated 3046 instead of the
726". Could anyone please tell me more about that alternative design 
(schematics, ICs pin-outs...) so that I can modify the design
accordingly ?
Actually, I decided to go for the Formant VCO because I still
have 8 copies of the 726, bought 15 years ago and never used.

Actually, I'd like to get feed-back on this posting : 
there might be some improvements in the original circuit design
(replacement of the 726 for instance) and I could modify the PCB 
design to fit the most interesting improvements. But I'm doing
this on my spare time and won't be able to spend weeks on it.

Someone asked "Would you be willing and able to have some boards
made and to sell them to people on the list?" ...
Well... I never thought of that... Actually, the original file
for this PCB is PostScript on the Mac. This way I can make very
high quality film (1270 dpi) on a linotype and use it to make the
board (through a not-too-expensive local service company).
But I intended to do that for my personal needs only. I wonder how
much people would agree to pay for that... And I'm afraid it would
be too much stress to run such a mailorder service...
I really don't know. I'm also wondering whether there isn't any
copyright transgression in selling modified PCB designs of
schematics designed by someone else.

May be the voltage-controlled police will knock at my door the next
morning ?

Or perhaps should I swap one finished board for a bunch
726s ;-)

Cheers

jbv