Friday, April 22, 2011

Some recapping on the Poly-61

Nasty caps
So, while I had my Poly-61 open and I replaced the buttons, I noticed some of the caps didn't look too healthy...

This was on KLM-477, which I think handles volume control and stuff like that. Here are some more from that board.

I don't know if the synthesizer has been standing on its side, with this side down, and the acidic vapours from the battery has affected the capacitors, or if they are just bad, since none of the other components seemed affected by it.
All the other boards looked fine as well, at least as far as I could tell.
Either way, I decided they needed to be replaced. While I was at it I thought I might as well change all the electrolytics on the PSU board as well.
So, I ordered some caps, replaced the ones on the PSU board and KLM-477. I never took a photo of the PSU caps though.
The old caps have some insulating adhesive soft plastic sheet on top of them, which I of course didn't put on the new caps (because the adhesive was bad), but they are a bit shorter so I'm guessing it's not really needed now.

I need more space!!
Again, I got reminded of my lack of proper space in my apartment...

Luckily, I just signed a contract for a new apartment. :)
I am moving on the 15th of June! YAY!
I'm going to have a room dedicated to my music and electronics stuff! WOOOOOOO!!!
I can't wait! :)

Anyway, here's a pic of some of the new caps in place. Not much to see really, but hey. Just as proof...

It's the replacements for the ones on the first photo.

Oh, and I noticed the keys didn't respond as well as they did right after my previous session... Damn it...
I'm gonna order some new repair-stuff and see if it does the trick ;)


  1. Hey! Good work! In the process of rejuvenatig 4 of them. (4 Poly-61's, not 4 capacitors!)

    Did you keep the exact same value for all capacitors?
    I know people sometimes put higher voltage caps in some key locations...
    Ex: the Alesis Quadraverb...

    1. I believe I used the exact same values for this as they were pretty standard values. You should too (no need to change anything that does what is should).

      Otherwise, it depends on what purpose the capacitor has.
      The easiest way is of course to keep the exact same capacitance and voltage.
      In some old gear it can sometimes be hard to find exact replacements, but just pick the closest higher voltage if that's the only problem. It's just a maximum rating and increasing voltage rating one "step" shouldn't affect the performance of the capacitor, though perhaps higher voltage ratings can influence other parameters of the capacitor (like ESR and size etc, though modern caps are smaller today anyway) slightly.

      I'm pretty sure that in basically any synthesizer from the 70's and later you should be able to find replacements with exactly the same capacitance values today.
      I would never substitute a capacitor for one with different capacitance unless I have looked carefully at the schematics to see what purpose it has (audio filters, LFO, oscillators, etc) and made sure I understand what happens if I would change it.

      But again, if you can't find one with the same voltage rating, buy one with the nearest HIGHER voltage.
      There shouldn't be any problem.

      Good luck!