[sdiy] Issue with a Moog Sonic 6, Help!

Quincas Moreira quincas at gmail.com
Sat Mar 11 00:21:19 CET 2017

Hello dear geniuses :)

I'm helping a student with his Sonic 6 and we have an issue I can't
diagnose, and maybe some of you may shine a light.
Mostly works, dirty pots and sliders will be replaced etc. It was a bit out
of tune, I measured the +-15v and they were a little under, so I trimmed
them to precisely +-15. OSC A sounded much more in tune. Then something
weird happened. OscB would go up high in pitch and not really be controlled
by the kb or any of the modulation sources. The keyboard makes it dip a
little and glide back up high. It's a weird keyboard, seems to actually be
outputing 5v/oct. When I turn the synth off for a bit and turn it on, the
VCO works fine for a few seconds then starts rising again. Ring any bells?
Hope so!
Thanks :)

Here's the service manual

Quincas Moreira
Test Pilot at VBrazil Modular
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