Cgs synth

On 02.03.2006, at 00:38, c10h14no2i wrote:

> I'm NO expert, but the first things I'd try is to be sure your power
> wires are all good. Test the voltage somewhere on the PCB where you
> know it should be getting +15 and -15. Then I'd replace the tl071.
> On mine, I had a few bad solder lands on the PCB. I built a bunch of
> CGS modules, and the filter was the only pcb w/ any problems, but it
> had 3 bad lands on it. I found the one causing the problem by taking
> a patch cable that was going into my VCA. I had the VCA turned up.
> Then I put a signal into the LP, BP, HP, inputs (not all at the same
> time) and took the cable going to the VCA and touched a bunch of
> points on the PCB. I finally found one where I got no sound, where
> there should have been sound. Traced it to the nearest component, and
> bingo.. there was the bad connection. I didn't go touching random
> spots w/ the cable.. but I followed the path that the audio takes.
> You probably dont want to connect +15 to your VCA :)

I debugged everything, after a tip from Ken i replaced the 2N2222 with
the right "TO-case" ones. nothing changed better.

Some questions do arise during the debugging:

a) I see the CV and FREQ IN at the "entry point" to the PCB, behind
the 220K (nearby the CV input’s) i just see _nothing_ at all, no wave
or power behind
the 220K ones. if i shorten the 220K it seems to "slightly" better
working.

Any more hints / ideas ?

i'll replace the TL071 now..