You know what ?... now I relaize I replaced IC8 and ICx11 as well !
What if the problem is related with only one of the VCOs...? lets say
VCO1. What would you check/replace ?
--- In
PolySix@yahoogroups.com, Johannes Hausensteiner <johau@g...>
wrote:
>
> If you already replaced Rx39/Cx10 then the only thing in common
> for both VCOs in one voice is ICx11 (TL072). THe value of Rx39
> is not very critical unless it is very different to the nominal
> value of 1k
>
> > By IC8 are you refering to ICx08 ? it's a 4558 opamp.
> No, I mean IC8, which is a 4051. It is common to all voices; it
> demultiplexes the CV for the VCOs
>
> Johannes
>
>
> gil_we wrote:
> > Thanks !
> >
> > The Cx10 and Rx39 have been already replaced to no avail.
> >
> > By IC8 are you refering to ICx08 ? it's a 4558 opamp.
> >
> > btw, I now see that I had to replace Rx36 with a slightly
different
> > value because even after the machine is warm enough, with the
> > original value the related VCO still cannot get tuned with the
other
> > oscillators, not matter how you set the VCO tuning trimmers.
> >
> > Thanks again.
> >
> > --- 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
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>
> >>>>
> >>>>
> >>>
> >>>
> >
> >
> >
> >
> >
> >
> >
> >
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