Restoring rubber keyboard on a logic analyzer

[Paul Koning]

Gentlepeople,

I have a Philips logic analyzer (PM3585) which is about 20 years old at this point.  It seems to be basically functional except for the keyboard, which unfortunately is a critical part.

This is one of those molded rubber type, with a circuit board behind the rubber that has contact areas made of carbon film (at least they are black in color) and on the back of each key a small cylindrical bump also coated with carbon. Some of the buttons work but most don't seem to even if I press hard.

I've disassembled the keyboard, which was easy enough.  Inspection shows no damage and no signs of corrosion or contamination.  I wiped everything with isopropyl alcohol anyway.  The result is no change in behavior.

Any suggestions for what to do next?

	paul