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
> > >>>
> > >>>
> > >>>
> > >>>
> > >>
> > >>
> > >>
> > >
> > >
> > >
> >
>