I've just picked up a cheap HP-28S. When I first turned it on I got a normal looking display.
I then turned the calculator off and opened the battery cover to check for corrosion. (It appears thee once was some...)
On replacing the battery cover and turning on the calculator I was greeted with a single black line across the display that slowly faded. Then nothing. The system reset doesn't work.
I think that maybe there's some corrosion inside, and I'd like to open it up to check it out (and clean it up).
Can these calculators be opened?
How?
Any other thoughts on the problem. (the batteries are OK)