1974 minimoog contour gen issue

[coolcatguy]

my minimoog was relatively recently fixed up by a competent tech (basics like replacing caps, etc) and working perfectly fine for the better part of a year. i moved and didn't use it for a bunch of months and now the contour generator seems to have stopped functioning. i am a competent tech myself but the specifics of the contour gen have me a bit stuck. basically, the key trigger is working fine (-10V to 10V) but am getting 0V at the collector of Q20. i have replaced all of the transistors on the pcb with appropriate types, CR10 (which was cracked but functional) and a few carbon comp resistors. the only other slightly odd thing is that my 15V rail is a bit higher at just above 20V so that could possibly be contributing to the issue. any thoughts?

[Markyboard]

Are both contour generators not working? How about just the attack portion? I would check the decay switch and s-trigger input circuitry - It may be shorted. Try disconnecting and reconnecting the Cinch-Jones connector from the left hand controller.

[coolcatguy]

Are both contour generators not working? How about just the attack portion? I would check the decay switch and s-trigger input circuitry - It may be shorted. Try disconnecting and reconnecting the Cinch-Jones connector from the left hand controller.

i had checked the decay switch prior and it was ok. after plugging in again, Q26 (in the decoupling circuit) let out the magic smoke. i was using exact part replacements but purchased them from tayda a few years ago and after checking them out, the 3392 must have been rebranded because the pinouts did not match what they should have been anyways, replaced everything with 3904/3906s and it was good to go! this was my third reminder to not buy active components from tayda (after receiving fake jfets many years ago and then faulty TL072s last year) so rest assured i will not make that mistake again.

[Markyboard]

Cool- glad you resolved it.