Discussion about the Korg PolySix synthesizer

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
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>
> >>>>
> >>>>
> >>>
> >>>
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > PolySix "Digiest" Page: http://www.acc.umu.se/~amber/Poly6 
> > Yahoo! Groups Links
> > 
> > 
> > 
> >  
> > 
> > 
> > 
> >
>