42S won't self test or turn on after turn off (Problem Solved)

[Bruce Larrabee]

I have a 42S that won't run any of the self tests. It also won't turn on after turning off (you have to remove the batteries to turn it back on). When ON all the keys work.
Functions I have tried function but won't run self test.

Any ideas.

Problem solved: calculator had two keys shorted. Repaired and now working.

[aj04062]

My guess is the PCB to Keyboard contact is failing. If you press and hold in the middle of the calculator below the LCD does it behave normally?

[Bruce Larrabee]

I've already replaced the PCB to keypad interface. Please note in my original post, 'When ON all keys work." Get it?

[Geoff Quickfall]

"When on, all keys work"

Got it, funny though, I had one that would turn on, function perfectly, but not turn off! It was the contact foam problem.

However, you have repaired the contact foam, and since the repair must be presumed to be perfect; it sounds like an IC problem.

Without, I assume, any electronic testing equipment available, I would re solder (quick melt of each connection) the IC's to rule out a cold solder. This might have ocurred when you disassembled the unit to repair the foam contact. Stressing the board could have caused the solder break quite easily.

Cheers

[Bruce Larrabee]

Well 'perfect' is a strong term for any repair, but thanks....

That is good advice. I'll try that. It has worked for me before .

I do have electronic test equipment, including stuff I build to diagnose specific calculator series. So if you have any tests you'd recommend let me know. Thanks