Korg Polysix Synthesizer Key Repair

Korg Polysix Synthesizer
Korg Polysix Synthesizer

This week I had an offer to buy a used Korg Polysix with keys that were completely dead. In addition, a few of the program buttons were not working and the original blue battery inside was showing signs of starting to leak. Despite the issues and already owning one excellent Korg Polysix, I took the plunge. I just couldn’t beat the price. The Korg Polysix is one of my favorite analog synths and when they work well, they work very well! It’s just a joy to play.

My initial thoughts were that with the excellent price I got for the Polysix, I could at the very least use it for parts. As I progressed with the repairs, I quickly changed my thought process and soon realized, I had a VERY good working Korg Polysix on my hands.

First up was the issue of the battery. Immediately after I received the Korg Polysix from the post, I open up the box, threw the synth on my work stand, and opened it up. I didn’t even plug it in once to play it. I then grabbed my fine tip cutters and gently yanked that battery sucker right out. Good riddance!! My regret was that I couldn’t yank it out any faster…laugh. If you ever buy a Korg Polysix with the big blue battery in it, I can’t stress enough to get that thing out of there quick. The areas around the battery are just too sensitive to lose to battery acid. Sure there is a KIWI replacement board available, but I wasn’t much in the mood to pay another $450 with shipping to get one. I then inspected the outer perimeter of the PCB board and found no damage from the battery. That was close!!

To replace the battery I temporarily attached a 3.6V rechargeable phone battery. I did the same thing with my Korg Poly-61 and it works great. There is a way to get a lithium battery in there, but I’m currently awaiting for a new supply of Diodes to make the repair. Until then, the phone battery works the same, but without the leak problem. I also soldered wires away from the PCB boards so that I don’t have to fiddle at all with that sensitive circuit board. I then loaded up some cool patches into the Polysix and called the battery changed complete.

The next part of the repair was dealing the dead keys. Every single solitary key on this Polysix was completely DEAD! I scratched my head for a minute and thought great! I probably have a chip or wiring problem somewhere. After some research on the web, I soon discovered that the Polysix had a notorious problem with bad key contacts. Some even say the vapors from the leaky battery can cause a complete shutdown of the keys. Geez, I better not get a whiff…laugh. Fortunately, the Korg Polysix is probably one of the easiest synthesizers ever to work on with regards to accessing the keys and key contacts. Super simple!

What I found was exactly what was written on the web. I had to replace the black carbon contacts on the silicon rubber pieces along with cleaning the gold contacts on the pcb board. Fortunately about 3-4 years ago I had bought a sheet of those carbon contact stickers from the SoundDoctrin that never worked for my Juno-106. I had them tucked away wondering if they ever really would work on anything! I had nothing to lose and so after replacing a small test section, I shockingly noticed that every single key with the replacement contact sticker had perfectly come to life. I then proceeded to replace the rest and now I have a perfect working set of Polysix keys. Absolutely amazing!! Note I also ordered some CaiKote 44 Conductive Coating off Ebay which I read works the same. I have no doubt that it does so I’m very glad to have a bottle on the way as I’m now out of the carbon contact stickers. Note that those stickers were originally used for the Polysix by the SoundDoctrin so they were definitely suppose to work. Note that spraying DEOXIT will not work and will actually make the contacts worse. I know that because I sprayed a sample and that screwed things up, so I had to give that section a thorough cleaning. Thus the Korg Polysix key problem was solved.

Finally I had the program button problem. By this time I was a bit tired and simply wanted to play the Korg Polysix. I read that shooting some DEOXIT in there could do the trick. Although not 100% yet, I can happily report it brought back the buttons and I can now at least change them when needed. It sometimes requires a couple of presses, but overall they work well and I’m ok with the result. I did do some research though and those buttons are not an easy task to fix or replace. It does require some soldering and finding a new button or contact. This is a case where I would seriously either try to fix what you have or just make do with it.

Thus I now have another 100% working Korg Polysix that is in excellent condition. Even the side wood panels are not broken like a little on my first one. I played them both last night with one using the ARP and the other playing a melody. It was simply awesome. I used a TR-626 to sync both with my Yamaha RX5 and it totally rocked!

The Korg Polysix is basically a very simple synth to repair provided you don’t have a damaged PCB board from a leaky battery. If you do, it’s still possible to have the board replaced by purchasing the expensive KIWI upgrade kit. The keys and buttons are definitely fixable. The keys are extremely easy so if you find anyone trying to dump a Korg Polysix on your lap because all of the keys are broken, take it!! The problem is minor at best.

Here is a link to the post about my first Korg Polysix. This particular one had chip problems which I fixed. It’s now in perfect working order.

Here are the patches I have and use for starting out with the Korg Polysix. I use these for templates and highly recommend them.

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