Discussion about the Korg PolySix synthesizer

First thing to do is check (with a scope) ICs 18 and 19, which provide 
the demultiplexed signals for those CVs.
4051 CMOS ICs can become intermittently faulty over time;  also, since 
the two are connected to the same A,B and C lines, one bad chip can 
affect the other.

~G

vib.ration33 wrote:
>  
>
> Hello,
>
> I've been a P6 owner for about 15 years. The machine was thoroughly 
> checked when I bought it, and the infamous battery was replaced before 
> any damage got done. The machine has been in perfect order (except the 
> pots have begun to have slight contact problems).
>
> Today when I decided to power it up again (the machine has been 
> resting in the studio for a few months) it worked well for about half 
> a minute or so, and then the cut-off pot ceased to have any effect.
>
> Interestingly the speed/intensity pot didn't work either. The weirdest 
> thing is that now Envelope Attack pot actually acted like the 
> speed/intensity pot, and Decay pot controlled the cut-off of the filter.
>
> All of the other pots in EG and EFFECT sections work ok.
>
> When I switched the machine on and off again, everything was again 
> fine for a while. Besides of the little delay when the problems start 
> the symptoms are at least that cut-off and intensity pots cease to 
> work completely and other pots take their place.
>
> When in the problem zone the Attack and Decay pots have double 
> function, they also control attack and decay besides cut-off and 
> intensity.
>
> All of the other pots and switches work fine and the memory is ok. The 
> intensity and cut-off values are recalled as they were.
>
> I just observed another interesting phenomenon: when tape is enabled 
> MG Speed slowly ramps up to maximum speed. The ramp ends when tape is 
> disabled. I can make this can happen before entering the problem zone. 
> Sounds great (when modulating a resonating filter) but I don't think 
> thats how it should work :)
>
> Another observation: the cut-off pot doesn't cease to work instantly - 
> instead its range gradually diminishes (in 10-15 seconds) to zero.
>
> Any recommendations where to begin? Sounds like the synths is a little 
> imbalanced, maybe a capacitor or resistor somewhere needs to be 
> changed, or there is a creeping short-cut somewhere??
>
> 



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