Hi. I recently got hold of a Moog Prodigy (336BX) after wanting one for a fair old while and am thrilled with it apart from the fact that oscillator 1 seems to be playing up and I’m hoping somebody here might be able to shed a bit of light on the issue.
Oscillator 2 works absolutely as it should as do the mod/pitch wheels, keyboard, filter, contours and everything else. When the oscillator 1 volume is turned right up and osc 2 is right down I can sometimes hear a high pitched static hiss when any of the keys is pressed but the pitch of this sound doesn’t seem to be affected by the keyboard. The keyboard does affect osc 2 and self-oscillation as I say though. I also get a slight crackle if I move the osc 1 waveform switch whilst pressing any of the keys. Finally when switching the sync switch to ‘on’ the sound from osc 2 disappears as well no matter where any of the volumes are set.
If any more information is needed to have a go at diagnosing this problem then I’ll try my best to provide it.
my Prodigy shows the same behaviour. I bought one on eBay, and after receiving it it worked for exactly half an hour
Suddenly, the same as you described. I opened it and found two LM3046 on sockets. I put the first LM3046 into the second socket and vice versa. The problem moved from oscillator 1 to oscillator 2. Oscillator 1 was happy again, and now Oscillator 2 whistled in supersonic ranges. Conclusion: the corresponding LM3046 is dead.
I replaced the obviously dead LM3046 by a CA3086, but that didn’t work. So I orderd some LM3046 from a german supplier. I should receive them in the next days, and I hope this will fix the problem.
Just a note that generally a 3086 should work fine instead of a 3046.
There isn’t a big difference. The 3046 is very slightly better on temperature specs, but hardly worth mentioning.
Fwiw, there’s also the military version, the LM3045J.
I stock the CA, LM and the J versions, but as you’ve found, they’re available if you look around.
Good luck.
I just got the LM3046 and I immediately exchanged the dead one. And - both oscillators sing in a duet again.
But there is another problem in the modulation oscillator. The modulation only works from time to time and very scratchy. Perhaps I must resolder the switch or pot or some other parts.
I’ve just tried this very same thing thanks to your tip and am pleased to say that I think you’ve just saved me hours of poking around inside this thing testing components and pulling my hair out. Thanks so much for your help, I really appreciate it. Can’t wait to have it working properly.
Probably just a case of a dirty potentiometer of the mod wheel. Just shoot some Deoxit in it… (I know it’s not a permanent solution, but it will work for a while, until that pot is replaced by a new one perhaps.)
