Discussion about the Korg PolySix synthesizer

Hi Peter,

I¹d say you still have some data bus chaos going on with the Œ367. Do you
have a logic probe? Shunt the test point with a 56K resistor on the PSU,
turn VR1 on the Œ367 so that at least some of the LEDs come on. Then, using
a logic probe, scope each of the data lines D0-D7 and write you result down
in your next post. Don¹t have a logic probe? Get yourself one. You will find
it no end of uses for it if you are going to maintain your Polysix!

Cheers,
Andy


On 15/05/2011 01:10, "Peter Mörck" <peterm@sunsetselection.com> wrote:

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> Hey group!
> 
> I have been recapping an old Polysix which was given to me for free in pretty
> bad shape. I have repaired some 3 bad traces under IC31 on the CPU board and
> also an odd corroded trace on the effects board. IC31 was removed and replaced
> with a socket and a 74HC08. The switches on the panel are replaced and all
> electrolytic caps are replaced.
> I have removed the old battery and just put 2 wires in (insulated in the ends)
> until I have a Li-battery to put in, which I will place away from the board on
> a small separate board :) I also removed C40 and replaced R91 with a 1N4148 in
> preparation.
> 
> Except for the keyboard which needs a good cleaning and fixing, everything
> responds well, I mean all the controls, write to memory, banks, programs
> (haven't tried tape interface though). So as far as I can tell, it is fully
> operational (except keyboard).
> So I thought it was time to run the calibration since I've replaced a lot of
> capacitors and it doesn't track well, plus one voice is a lot louder than the
> others.
> 
> I run into "problems" right from the start. After attaching the 56k resistor
> and turning the Polysix on I adjust VR1 on the CPU board.
> Bank A LED and Program 1 LED on... I turn... Program 5, 6, 7 and 8 LEDs light
> up, but NOT program 2,3 and 4.
> I know the LEDs work, I've switched around before, I've saved to Bank A Prog
> 2. Everything looks fine, but those LEDs won't come on during this
> calibration. Seems very strange to me. Anyone have any ideas?
> I even see LEDs 2,3,4 blinking very briefly sometimes if I turn VR1 back and
> forth across the point where all LEDs should light up.
> Oh, and the LED on Key Assign Mode are a bit inconsistent in their behavior
> when the LEDs switch when I reach the proper calibration point. Sometimes
> another one lights up, sometimes three of them.
> Also the bank LEDs don't change. Only bank A LED is on but I've seen Bank D
> LED blink briefly as I cross the "calibration point".
> 
> I measured across the zener D2 and I get 3.54V when I have 4.99V on the 5V
> rail. I would expect that can be affecting the calibration point but I find it
> hard to imagine it would keep program LEDs 2,3,4 from lighting up.
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> The machine seems to work find but obviously this seems to indicate some
> fault.
> I think I will continue with the calibration procedure anyway and hope it will
> work out ok.
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> Anybody have any ideas why not all LEDs light up???
> 
> Thanks for reading my wall of text :)
> 
> /Peter
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