Discussion about the Korg PolySix synthesizer

Juhannes, back to the second VCO tuning problem,
are the caps you mentioned suppsed to be of special make or 
temperature resistant, ot does just about any polyester caps will do ?




--- In PolySix@yahoogroups.com, Johannes Hausensteiner <johau@g...> 
wrote:
>
> Hi,
> 
> The caps are Cx10 ... where x is the voice number. On the schematics
> only voice #7 is drawn in detail, so you can see C710. Maybe it is 
not
> the cap but the accompanying resistor (R739), or the demux (IC8).
> 
> This is a great machine. Two really independant VCOs!
> 
> Johannes
> 
> 
> gil_we wrote:
> > Thanks very much !
> > 
> > The tuning is bad on both VCO1 and VCO2 of that oscillator 
(although 
> > it seems more extreme on VCO2).
> > 
> > I uploaded the schematics diagram for the VCO board to the files 
> > section - what would be the caps to check on that one ?
> > 
> > Thanks again.
> > 
> > 
> > --- In PolySix@yahoogroups.com, Johannes Hausensteiner 
<johau@g...> 
> > wrote:
> > 
> >>Hi,
> >>
> >>I only have the schematics for the MK I; which I do not know 
whether
> >>it is similar to the MK II. Which VCO has the problem? Is it VCO-
1 or
> >>VCO-2 or both? If it is both then have a look at the hold 
capacitors 
> >>after the VCO CV demux IC15 (a 4051) on KLM-301 board.  These are 
the
> >>caps C25 - C32.
> >>
> >>Good luck,
> >>
> >>Johannes
> >>
> >>
> >>gil_we wrote:
> >>
> >>>I've been recovering this one, found in the flea market. Overall 
it 
> >>>had about 8-9 different faults that I fixed, leaving two 
problems.
> >>>
> >>>The first is a bad SSM2056 chip which I need to find. The second 
i 
> >>>probably inherent in the discrete ciruit of the second 
oscillator.
> >>>
> >>>Upon powering it up, that particular oscillator will be out of 
tune, 
> >>>till it gets to its max. internal temperature where the tuning 
of 
> >>>that VCO is geting more or less - stable.
> >>>
> >>>All other oscillators are immediately in tune, no matter what is 
the 
> >>>temperatue inside the machine.
> >>>
> >>>I, of course, tried to figure out what the bad component is by 
> >>>blowing with a straw on each and each of the suspected 
compnents, but 
> >>>blowing on every component on the circuit of that oscialltor 
which 
> >>>seems to be pitch related, seems to effect the pitch.
> >>>
> >>>I also tried to switch transistors between the bad oscillator 
and 
> >>>another (working one) but the problem persisted.
> >>>
> >>>Does anyone have any other idea / direction ?
> >>>
> >>>Thanks
> >>>
> >>>
> >>>
> >>>
> >>
> >> 
> >> 
> > 
> > 
> >
>