Hi all,
I'm pretty much a lurker here because I never had a polysix (and still don't, and would like one!), but I did just acquire a Poly61 with issues for $25.
Of course, the keyboard worked very poorly AND the NiCd was slightly leaking (classic problems, I gather). I snipped out the NiCd, recycled it, and cleaned up the PCB with DeOxit. There wasn't much corrosion and the unit works fine. I just wanted to get the corrosive electrolyte(?) off the board to avoid future issues.
But I digress. I'm posting because the way I repaired the keyboard was to remove the key PCB from the Poly61 and replace it with the key PCB(s) from a Korg DW-6000 that I sacrificed a year ago. The difference between the key PCB from the two units is small:
1. the DW6k has two PCB's joined by ribbon cable, the p61 is a single PCB
2. the DW6k PCB has a carbon shorting pad underneath the rubber domes, where the p61 PCB used gold plate.
This last difference, I think, is the reason why the p61 have such keyboard troubles. I think the metal shorting pad passivates and is a smooth surface, so over time, the carbon on the rubber dome makes a less and less conductive connection. The DW6k's carbon is rough and maybe doesn't passivate, so it should be a more reliable connection over time. At least, I've never heard of the DW6k's keys having triggering trouble, but on the p61, it's a classic problem.
Note that the DW8k doesn't have the same type of keyboard - it shares the keyboard with the DSS-1, if not others. So if you do this, you have to find a DW6k.
In sum, I think my p61's keyboard should be more robust over time now that I've Frankensteined in the PCB from the DW6k. If I do run into unreliable performance, I'll definitely post back here.
Thanks!
PS what happened to the rest of my DW6k? Part of it is here:
http://www.flickr.com/photos/37595587@N00/sets/72157616967698662/