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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