Moog Music Forum

Opus 3 I'm trying to repair's String section and Chorus doesn't make a sound, I've tested all relevant chips with a Multimeter and they all seem to be ok, I read in another post to maybe test the mix slider with an audio probe and I will but if that's not the problem, where else should I look? Wiring path?

Yes. Follow the rabbit. You need an oscilloscope. The service manual shows the components. First look at the master oscillator output. If you see the HF wave, check the 12 top octave chip outputs with the 12 semi tones. Follow the outputs to the dividers and check their output as well, then check the following mixer section etc. etc. until you find the point where the signal vanishes.
The service manual contains a good description.
My assumption is that a summing opamp within this path is dead. I've seen this in other synths.

We changed out the Strings Mix To Chorus slider, but now we are getting a lot of distortion on the Strings and Organ. Still trying to figure out why.