Restoring rubber keyboard on a logic analyzer

[Paul Koning]

> On Apr 26, 2018, at 12:32 PM, Electronics Plus via cctalk <cctalk at classiccmp.org> wrote:
> 
> Easier solution is to apply some conductive light lube. Radio Shack used to
> carry it, and I repaired a LOT of remote controls with it!
> 
> Cindy

I made a successful repair.  Here are the steps I used:

As I mentioned, I tried cleaning with isopropyl alcohol, without much success.  

I realized that I could test the rubber contact points with a multimeter, probing two spots on the surface.  The offending keys had much higher resistance or simply tested open.  That made it easier to try other options without having to assemble/disassemble each time.

I found a spray can of "contact cleaner/lubricant" and tried that.  OOPS.  Made it much worse.  Looked at the ingredients: one is "mineral oil".  Ok, so that's fine for metal wiping contacts I suppose, but not for this.  Washed the keypad thoroughly with dishwashing soap and water, then wiped several times with alcohol, that got me back to where I was.

Then I realized I still have a tube of powdered graphite (the stuff sometimes used for lubricating locks, though it turns out that's not a good idea.  Squirted some onto a Q-tip and rubbed the bad contact pads with that.  They look shiny as a result rather than dull black.  But it works!

So that's the answer: graphite powder.  I now have a working analyzer again.  It will be interesting to see if the graphite wears off eventually, I suppose it might but that's ok, I can just do it again.

Thanks everyone for the suggestions.

	paul