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HP Forum Archive 04

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HP41 display problem
Message #1 Posted by Andreas Schultze on 3 Oct 2000, 4:41 a.m.

I've got a display problem with my 1980-HP41C. After a battery leakage, I opened the Calculator and cleaned it very carefully. Now it looks like new, but when I turn it on, the display shows only the lower part of the characters for 1 second, the the display fades away. As long I have a key pressed, the display is OK, when I release the key, it fades. It is only a display problem, all calculator functions are OK. I already re-soldered the display-contacts, which were etched by the battery acid, but it didn't help. As far as I know, LC-displays need an AC voltage at the backplane to operate. Maybe this is a hint? (please excuse my /&$"%/$/%$-English...)

      
Re: HP41 display problem
Message #2 Posted by Gianmaria (Italy) on 3 Oct 2000, 4:58 a.m.,
in response to message #1 by Andreas Schultze

Hello Andreas, I experienced the same problem. In my opinion the problem could be the unstable contacts between the keyboard and the CPU board. You could polish that contacts and replace the lower screws with others bigger (not too big!) to assure firm contacts. Let me know how happened... Greetings. Gianmaria Porrini (ITALY)

            
Re: HP41 display problem
Message #3 Posted by John Robinson (Australia) on 3 Oct 2000, 8:14 p.m.,
in response to message #2 by Gianmaria (Italy)

Hi Andreas,

I agree with Gianmaria on this one, it's not a problem with the display, but rather poor contact between the CPU board and the ketboard PCB. Just clean all contacts with a good circuit board cleaner. Make sure the lower two screw posts are not cracked/broken, and when you assemble the case, make sure the screws are good and tight.

Cheers, John


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