Sonic 6 pitch drift...

The Moog Forum Moog Music General Topics Forum
1

Hi folks,

Question for the tech’s on here… I am looking at a Sonic-6 and was hoping someone here may have come across this one… it isn’t holding it’s pitch on a slow release.

Strangely the high notes drift down and the low notes drift up. Middle of the keyboard notes are less affected. I’ve checked the keyboard pcb and all looks well. I changed the hold cap, no difference and I also changed the dual FET, put in a new 2N3954 - (the old one was actually an E400)… and it’s still the same.

Any ideas anyone please…?
Cheers.
Tom

2

Check for any flux contamination anywhere in the keyboard S&H circuit. That is a known problem with any analog keyboard. Flux creates an impedance that drains off the capacitor hold voltage.