Thanks!
I was actually able to remedy the main problem. Some rust or similar substance connected pins 11,12 and 13 in the connector CN10, which connects KLM-367A to KLM-371. The synth doesn't go into the problem zone anymore.
The soldered points of that connector on 367A board look a bit rusty too. The points have deep brown colored flange, so I suspect the soldering points on the board could need cleaning.
The board just close to the connector looks a bit odd, slighly bulged. A few threads of light brownish substance are spread over the connecting wires, which go to the soldering points of CN10.
The board's backside looks ok.
I don't think I have good enough tools at hand at the moment to actually remove and clean CN10 (or do any scoping). What would be the best way to proceed with that?
Tape enable switch still resets the synth, and ramps up MG. Now the ramp happens without the level being at maximum like it was before. Ramp begins when tape is enabled and synth resets when Tape is disabled.
--- In PolySix@yahoogroups.com, klosmon <klosmon@...> wrote:
>
> 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??
> >
> >
>
>
>
> [Non-text portions of this message have been removed]
>