Moog Source Bad Oscillator

[Jacob Hunt]

Oscillator 1 on my source has quit on me. Before it went completely out it would fail to switch to triangle wave, now it doesn't make any sound for a while. After warming up for a long time, it makes a very high pitch FM type sound and slowly comes down closer to the note it should be, but is pretty unsteady. Osc 2 is perfectly normal, and everything else is fine, just osc 1 is bad. I have swapped around a great many of the ICs on that board, including all of them in the osc 1 section according to the schematics, but no luck.

Does anybody have any possible clues? Any help would be greatly appreciated.

[Jacob Hunt]

Still no luck
Does anybody have an idea what to look at? Is it possibly a cv issue?

[synthparts]

Did you try replacing the 3046/3086?

[Jacob Hunt]

I have, with no luck. I turned the osc. 1 temp trimmer, and it came to pitch, and so fooled around with some of the temp. circuit parts. It seems like it may be better now, I'll wait and see how it does over time.

[Jacob Hunt]

Touching or blowing on any of the temperature circuit parts makes the problem come back, after it takes it's warm up time. This doesn't happen for osc. 2. I don't know much about the temperature circuit, but something must be bad there, just don't know how to tell..

[Jacob Hunt]

Well, replacing the transistors, diodes, and the 4558 in the temp. And osc. 1 circuit has greatly improved things. Osc. 1 comes in in seconds rather than a half hour, so after a normal warmup time, it's good to go