Archive of the former Yahoo!Groups mailing list: Discussion about the Korg PolySix synthesizer

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.

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.

Anybody have any ideas why not all LEDs light up???

Thanks for reading my wall of text :)

/Peter


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