Discussion about the Korg PolySix synthesizer

Problem solved !

It was wrong types of capacitors used for x08 , x09 and x10

Schematics says they are supposed to be polypropelene... used ceramic 
or polyester...

Got some high voltage polypropelene in and viola ! Tuning stability 
is back !

Thanks !!




--- In PolySix@yahoogroups.com, "gil_we" <gil_we@y...> wrote:
>
> 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
> > >>>
> > >>>
> > >>>
> > >>>
> > >>
> > >> 
> > >> 
> > > 
> > > 
> > >
> >
>