calculator key bounce


What can be done with my old HP-35 that double enters a digit when I press the key. This happems for about half of the number keys. The 2 seems to be the worst, and the function keys seem to be ok.
Any ideas as to how to fix something like that?


I'm fairly sure there was an article about servicing 'classic' HP calcs on this web site. The last method it suggested for improving key bounce was to use very fine sand paper _wiped_ (NOT rubbed) between they key contacts. I would try using some contact cleaner long before sand paper.

Although I have not seen key bounce, I've noticed that the keys on my HP67 seem alot more 'snappy' with fully charged batteries.


Interesting. When I put the AC adapter on the calculator, the key bounce diminished. I would never have guessed that.
But after overnight charging of the battery pack the seven key still gave double entry. The two is now perfect.

I read Steve Loboyko's article about classic calculator repairs. He mentioned using fine grit sandpaper to repair non-functioning keys. I did use 600 grit sandpaper and got the decimal point working on another calculator. (an hp-67) I don't think the sandpaper solution applies to key bounce. Whatever happened to Steve Laboyko anyway?


I have had good luck wetting a thick thread or thin string with 91% isopropyl alcohol (available at most supermarkets and drug stores, avoid the diluted 70% stuff) threading it under the silver metal dome of the offending key on the keyboard circuit board, and working it back and forth to clean out the gunk. Repeat with a clean and dry string. I use a broken sewing needle to get the string under the key contact.

This techinque does assume you are comfy opening up and working on the guts of your prized baby...

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