Saturday, February 26, 2011

Poly61 key rejuvenation

Replacing the buttons

The two boards with the 17 buttons. Replacements in the bag. Red write button cap already pulled.

Enough idling! I decided it was time to replace the set of buttons on the Poly61.
I had previously ordered a set of switches for the buttons from but never took the time to replace them.

Old ones out. New ones to be placed.

Well, now it's finally done. All the 17 pushbuttons work as they should, no double triggers, no non-triggers. Good as new! (well, they are actually new, so...)

Fixing the keyboard again
Now, the keyboard was still problematic even if I had tried to clean it before. This time I decided to skip the isopropanol treatment and try a more mechanical approach. I heard rubbing the PCB side of the keyboard contacts removed some stuff that just some alcohol won't remove, so I tried that. Seemed to work ok but not as good as I was hoping. I wanted better results! I found some 1200 grit sandpaper (more like polishing paper at 1200) and decided to try on the first contacts. I noticed how they turned from a golden yellow to a more pale tone, and then it struck me: I guess they are gold-plated, or rather, were... Back to the paper treatment!
I put the silicon contacts on and measured the resistance... Still above 500 on some. Grr...
But.. Perhaps the carbon surface was bad too even if I had cleaned it with alcohol earlier?
I decided to use the 1200 grit polishing paper on the small carbon surface on all the buttons. It got a bit better! A couple of the keys refused to improve well enough so I again used the 1200 paper on the gold plated contact but rubbed veeeery gently and just a very short time, then some regular paper and then it was ok. All the keys now measure less than 300 ohm, most under 200, when pressed. I guess that'll do!
I didn't take any photos during that process by the way, in case you were interested, but I guess you'll survive. You've seen the contacts before :)

Now what? More problems?
They keyboard now plays nicely and the buttons operate properly! Starting to look good!
But, I have noticed some other strange things. There are probably a lot of bad cable connectors in this thing because the envelope of a couple of voices started acting up. One voice had no release and another one had a much longer release than the others, but it went away after a while. Hmm..
Also, sometimes when I flip the panel back the audio output dies. Messing around with the PCB connectors near the audio output makes it come back so I guess I should go over those too some day.
Aaand.. the little rubber cylinders that guide the keys down are disintegrating and need to be replaced. I have to try using shrink tube some day.

But! The most important thing is that I can now PROGRAM and PLAY this synthesizer without really being bothered by any major defects. Yay! :) And, I use this "cheap" unit as practice because I guess the Polysix will receive the same treatment later. I'm not gonna go crazy with the 1200 paper on the contacts on that one, hehe...

Maybe next step will be to add the CHD MIDI kit? :)

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