HP 42s Bad Key - Advice Requested

[Pjwum]

Hi Bill!

I recommend to not open the case. Also please do not use any wires to clean something up. Eventually you will ruin the conductor foil underneath the keyboard. I agree that if there is an issue with solely one key (except ON), the foam pad might not be the primary cause.

Remove the batteries. Bath and clean your device with the lower three key rows in IPA and press the bad key multiple times. An utrasonic cleaner will help. Let it dry in warm conditions a week or so. If you are lucky, the key issue and the problem during start-up could be interrelated.

If the keyboard operates normally again and you still need to re-insert batteries before start-up then you might open the case and try to resolder the CMOS-RAM.

Does it keep memory when you take out the button cells? Are your batteries fresh?

Please post your results!

Patrick