[sdiy] korg polysix flakiness

[Oakley Sound]

 > basically, the bank d button and patch 4 button start to come on and 
the patch starts to deteriorate...

You probably still have corrosion on the memory board somewhere. The 
corrosion from the removed battery will cause these sorts of faults. 
Many of the corroded sections will behave intermittently before they 
fail altogether. I have even seen some corroded vias that behave a bit 
like leaky diodes. That would cause all manner of weird faults when 
feeding a CMOS input.

I would go through the whole board again, removing all suspect vias and 
replacing all darkened traces. If that doesn't work, you will need to 
look at individual ICs. The corrosion can transfer to inside the chip 
without any major exterior damage to the chips lead frame.

I should also add that the corrosion can also work its way into the pot 
boards and the effects card. The mechanism by which it does this is not 
clear to me since the connecting wires are normally left intact.

I guess its a similar electron transfer process to that one whereby zinc 
plates protect the bottom of ship's hulls. Dissimilar metal junctions, 
potential differences, and environment all playing their part.

Best of luck.

Tony

www.oakleysound.com