Moog prodigy no audio

worked great! then i opened it to adjust the vca trim. got that working perfectly, then there was a crackle and then no audio…


no led
no audio

+12.05v at c38
-16v at c39

i have the schematic but don’t know where to look next.

Any help would be amazing!

Andrew

-16V at C39 isn’t cool, I’d say.

My recommendation:

1.) Check the fuses
2.) Replace U21 (7912 voltage regulator)

If there is still no output, you have to crawl backwards thru the circuit until you finally reach the oscillators :confused:

3.) Check in’s and out of OTA U17 (VCA) with a scope. If there is an input, but no output, replace U17. If that does not help, check output of OpAmp U22A (VCA envelope out).

4.) Next would be the ladder filter…

… and so on

Amazing info. thank you!!


Andrew