Rebuilding ARP PPCs

Using FSRs (force sensing resistors) to repair PPC "proportional pitch control" pads for an ARP Odyssey Mark III

Because I am now one of those people who thinks they are very busy, I am just going to share a “quick tip” today.

In one of several Odysseys that we rebuilt recently, the “Proportional Pitch Control” pads (otherwise known as PPC, those three spongy white pads that Mark III Odysseys have) were so bad that no amount of cleaning could revive them. I finally was forced to look for another solution, and tried using some FSRs (force sensing resistors) and the results were great.

I was prepared to have to adjust some values of the mixing resistors following the FSRs but the ones already there were just fine. The FSRs I used are Interlink FSR-02 which I got from Digikey.

After cutting off the elements of the original PPC “sensor”, which appear to be just parts from inside a regular ARP slider, I glued the FSRs onto the original PPC PCB with a very thin layer of CA glue (super glue) applied with a Q tip, folded the “tails” around to the back and soldered a very thin (26awg) between each tail and the solder pads on the PCB.

If you’re doing this, the biggest challenge is how quickly the plastic that the FSR is made of can melt. With my soldering iron on 725, I basically melted the end off of the first one I tried to solder to almost instantaneously. Set your iron temp a bit lower and work very quickly and you should be fine.

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