Am 04.10.2015 um 18:47 schrieb Steve Wilson
lighterthanairflight@... [korg_mono-poly]:

> however, it's far more likely that the external heating resistor is
> bad (or the transistor controlling it is), perhaps a bad opamp in the
> control voltage circuitry, or even just old electrolytic caps.

To be honest: the most likely failure are the trimmers, they collect
dirt and the center trace can corrode - even the closed models.

If I am in restoring any old synth, then the first action is replacing
the trimmers with modern sealed cermet trimmers, if possible 25-turn
trimmers.


Florian

(and please everyone: forget the electrolytic caps fairy tale - drying
elco caps will happen under thermal stress. This is reality in a
professional mixing consol from the seventies, which wasn't switched off
while the last 40 years. Those consoles get quite hot (we measured in a
SSL G4000 an average temperature of 55 degrees celsius!), but in a
normal synth such temperature never will happen - even in a CS80.

If recapping is required then at old mylar caps or tantalum capacitors.
And if those go bad, you will hear and smell it.