Korg Mono/Poly

Am 04.10.2015 um 18:47 schrieb Steve Wilson 
lighterthanairflight@gmail.com [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.