HP-21 - Crazy numbers

[BusyCalc]

Hello!

OK, thanks.

I'll do it so the next time I open it. I think it'll be a good solution because I could see some green corrosion on the PCB under the ACT, where there is only about 1 mm gap.

One idea was to use dental floss to remove it, but it'll be easier to immerse it in vinegar and let the chemistry work.

I bought some time ago a special lack in spray to protect electronic circuits against moisture. Do you think it's a good idea to spray it after cleaning?

Regards!

Oscar