Moog Opus 3 Oscillator needs a kick start to start

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codystein9
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Joined: Thu Mar 31, 2022 2:46 pm

Moog Opus 3 Oscillator needs a kick start to start

Post by codystein9 » Fri Sep 02, 2022 3:08 pm

Im working on a Moog Opus 3 that Im having issues with. I prematurly recapped the whole machine and cleaned all the tar crap off before troubleshooting the issue, not smart. For some reason the multivibrator/oscillator will not start up on power cycle. I found out I can couple my oscilloscope to the output and it seems like if there is a small spike when it connects, the oscillator starts up and the unit works flawlessly..until another power cycle.

Ive done quite a bit to try and solve the issue and I have a thread over on music-electronics (RIP Enzo).
https://music-electronics-forum.com/for ... t-to-start
Ive tried replacing the coupling capacitors, the oscillator chip. Someone suggested the chip needs a clean 6V in 100uS, which I record it coming in around 700uS and Im not sure how to speed it up any more. Ive replaced all the tantalums with low esr, the filter capacitor with low esr and the regulators. It seems like it gets to 2 volts super quick and then takes 600uS or so to get to 6V.

Im mostly a tube amp guy, trying to expand my knowledge base and work with other stuff, this seems to be above my pay grade. Id love some where pointers.

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