Erratic HP 9100B

[TASP]

I was in sparky school around 1982, if I recall correctly (LOL), in that era we were using an aerosol degreaser/cleaner to clean the circuit boards we made and worked on. I know it cleaned up rosin core solder residue really well.

I can't remember the exact hydrocarbon/fluorocarbon that was in the spray, I am sure it causes cancer, was radioactive, destroyed the ozone, was derived from asbestos and killed puppies and kittens. Might want to wait for a way better answer than I'm putting here.

Your device, IIRC, is older still, so I don't know if stuff from the 80s would be safe on stuff from the 60s. Same for whatever they use today; would it be safe for something that old made of materials they don't make anymore??

I think you are on to something with the rubber crud needing cleaned up. Hopefully it is just conductive enough to mess up the 9100 logic. If it is corrosive too, you might have a far more serious problem.