Sunday, November 8, 2009

Korg Polysix

About three months ago, a friend of mine called me and said "Someone is giving away a broken Polysix for free". Huh? He told me about the ad where he'd seen it and I called the guy up...

Apparently it had "electricity" but something was broken. He was thinking of driving it to the dump to just get rid of it but I said I'd be right over and pick it up.
So, a few hours later I go there and he gives it to me. He was really friendly but didn't really seem to know anything about electronics as he mentioned something about "The sound being bad and that in bass amps you sometimes need to change the transformer. Maybe that's the fault here."
Hm. I took it home and tried it.

Front panel wasn't working properly. Every sound was like a random noise on a saw wave. Changing preset didn't do anything. A couple of keys were so badly aligned so they were sort of stuck together.

After reading on the net about leaking batteries in the Polysix I opened it up and took a look.

Obvious signs of battery acid damage on the board and some of the legs of the chips. Oddly enough the battery seems fresh and clean. I guess somebody has either replaced it and made a poor job at cleaning up the acid or maybe just attempted to repair it by replacing the battery. Either way, it is not working now.

I saw a repair made on a strip that probably had been completely dissolved.

I took out my multimeter and tested for connection between the chip leg and the next available thorugh hole on the copper strip. No connection. I poked the "repair" a bit with the test probe, and guess what :)

It just came off and bent back. Obviously not a successful repair.
With my morale boosted that I had found an obvious error and believing that this was the problem I remade the repair (yes, soldering to the chip leg directly)...

Well, the switches on the front panel now seemed to respond properly at least but the sound was still the same horrible noise. All the knobs seem to react and alter the sound. Filter cutoff seems to work as well so I assume those chips are intact.
I'll have to clean that part of the board thoroughly soon and try to find more bad connections as well as fix that "repair" properly and not solder to the chip directly. I suspect that might not be the only problem though so I might have to look for more.

Anyway, the current state of the Polysix is not much different from when I got it, that is "useless", except that the buttons are now responding (even if they seem like they could use a replacement).


  1. (Shameless plug): As you have seen, many a Korg Polysix has failed due to battery corrosion on the KLM-367 PCB. But don’t despair! Bring your Polysix back to life! Replacement KLM-367 PCBs are now available. These PCBs are exact clones of the original PCB, except that they take a new lithium battery which won’t blow up and ruin your synthesizer.

    Puchase a new circuit board here:

  2. @Jed: Hi! Yes I'm on the Polysix list already. I know about your board and have been wondering whether to it or not.
    But I figure, you know "If it ain't broken..".
    Anyway, I might order one just to have it as a spare in case. I'll have to wait and see if I can get mine calibrated first or what the problem is.
    Thanks for the advice anyway :)