Cgs synth

I've finally found time to look into the PWM issue with the REV0.4 PCB, and
all I an say is shame on all of you for missing the error!

The PWM input is connected to the DC (offset) output of the saw wave instead
of the AV (zero centered) output. It has been this way since a labeling
error back on version 0.1 or 0.2. Chances are all versions of the board need
modification, though that was an area in which several mods were carried out
on the Ver 0.2 board. (It is a section of the VCO I don't use in my own
installation, thus it escaping my notice).

Modifications to the REV 0.4 and (probably) earlier PCBs are as follows:

Cut the track between Pin 5 of the TL072 in the bottom right corner.
Jumper pin 5 to the Saw AC output terminal via a 100k.

It is possible to place the resistor in place of the link on the PCB though
the track modification is still required.

Ken
_______________________________________________________________________
Ken Stone sasami@...
Modular Synth PCBs for sale <http://www.cgs.synth.net/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>

Hi Ken - yeh tried the mod and voila all problems solved. You wrote

Cut the track between Pin 5 of the TL072 in the bottom right corner.
Jumper pin 5 to the Saw AC output terminal via a 100k

I just used a jumper - is the 100k necessary between the saw AC output and pin 5 - it is not on the schematic. I have not checked it with a scope yet but it sounds ok without the 100k

thanks for looking into it.

cheers
Mike




[Non-text portions of this message have been removed]

Hi Mike - the 100k is there to protect the op-amp input in the event you
accidently plug two outputs together. Chances are you would survive without
the 100k, but these days I like to make things as bullet proof as I can.

Ken