[sdiy] Oberheim 4-voice issues (SEM, keyboard)

[Eric Frampton]

> I've seen 3086'es blow up before so i'd change it and see.

I tried swapping it out for a new one; no change in behavior.

> (ouch! hangover!)

Well-earned, I hope!

> but if both oscillators aren behaving the same, look for any components shared by the two oscillators.

As best I can tell the 3086 is the only part that's shared.

> What kind of keyboard is it? Sounds to me like it's a j-wire two-bus system? In that case, check for the wires under the affected keys and see if the wire going to the gate bus might have been bent.

It's a special version of a Pratt-Read; every J-wire is sent straight to a separate input in a mux'ing system.

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