Replacing Key Contacts on Korg Mono/Poly

When I first got my Korg Mono/Poly off eBay, quite a few of the keys didn't play.  After some searching around, I tried some CaiKote on the rubber key contacts (as I described here) and it worked great.  When I bought a Korg Polysix off eBay, it had the same problem...and CaiKote saved the day again.  But, now that it's been a few years, some of the keys on the Mono/Poly have stopped working again.  Let's fix this problem for-real.  Let's replace the key contacts!

New Key Contacts from LA Synth Co

When I first had my problem with dead keys, I couldn't find anyone who sold new key contacts for these old synths.  So, I had to use the CaiKote to restore the old ones.  That was pretty cheap and pretty easy.  I now know, however, that it's a fix that only lasts a few years.  In that time, LA Synth Co has started to sell brand new key contacts that fit a bunch of old synths from that era.  Fantastic!  So, $100 later, I've got a complete set to fit my Mono/Poly.  Let's take the old girl apart and swap in these new parts!

First, remove the five screws on the bottom of the synth to release the keybed.  Then, remove the screws holding on the metal panel so that you can get inside.  Finally, unplug the keybed from the Mono/Poly circuitry

Getting started is pretty easy.  As shown above, I unscrewed the keybed and the main front panel.  Then, I opened up the synth and disconnected the keybed from the circuitry.  At that point, I was able to pull out the keybed.

The keybed has been removed from the Mono/Poly.

With the keybed out of the synth, you can look at the side of the keybed and see how, when pressing a key, the key smashes down a gray rubber button (the "key contact") onto the circuit board underneath.  It is through this contact that the brains of the synth know that the human has pressed a key.

You can see how pressing a key acts to press down the gray rubber key contact.

On the underside of the keybed, you can see the brown circuit board.  The key contacts are attached to this board.  We need to remove this board to get access to the key contacts.

The underside of the keybed has a brown circuit board.  Remove the screws to release the board.

Removing the screws, the brown circuit board is easily removed.  Flipping it over, you can see all of the gray rubber key contacts.  They come off simply by tugging on them.

Removing the circuit board, the gray key contacts are revealed.

Pulling on the gray rubber strips, the key contacts are easily removed.

With the old key contact strips removed, now was a good opportunity to get out a little alcohol and clean the contacts on the circuit board.  I probably should have used higher quality alcohol (only 70%?), or something better than a cotton rag for my scrubber, but this is what I had.

Time to clean the circuit board.

With the board cleaned, I got out the new key contacts and lined them up to make sure that I had the correct assortment -- they're not all the same and I was worried that I might not have been sent the right ones.  Luckily, LA Synth Co know what they are doing.  I had what I needed.  They lined up great and I attached them simply by pushing them on.

Getting ready to attach the new key contacts

The new key contacts are attached simply by pushing them on.

With the key contacts attached, I start putting the synth back together again.  First, I have to re-attach the key contact circuit board to the bottom of the keybed.  The only trick is getting the key contacts to fit inside their respective holes in the bottom of the keybed.  It isn't hard, but you do have to pay attention.

These are the holes on the bottom of the keybed into which the key contacts must fit. 

After getting the board onto the keybed and screwed together, I did a visual inspection and saw that one key contact wasn't seated correctly (as shown below).  So, I unscrewed the board and was more careful in putting them together.  The second time, all the key contacts were seated nicely.

Here, after assembly, one of the key contacts didn't seat correctly.  I simply took it apart and was more careful when I put it together again.

That's it!  The key contacts are done!  The only thing left to do is to put the synth back together again.  I have to put the keybed back in, screw it in, and screw the front panel back down.

Time to put everything back together again!

Fully re-assembled, I also to this as an opportunity to clean the keys and the front surface.  Looks great!

The re-assembly went easily.  I also used my rag and alcohol to clean the tops of the keys and the control panel.  She looks great now!

Plugging her in, they keys all work.  The joy!  Not only is it a joy to play an instrument that works, it's a real satisfaction to have fixed it myself.  Fixes don't really come any easier than this one.  Thanks LA Synth Co!