|Re: Problems with HP41C|
Message #5 Posted by Victor Koechli on 21 July 2003, 9:54 a.m.,
in response to message #3 by hugo (belgium)
If your 41C is a fullnut (no rounded edges around the display - see the HP41 pictures in the museum), it has a second connector that could have failed. It's underneath the main electronics board. To get to it, you have to losen the two nuts that hold the board down. These also provide the pressure necessary to ensure contact between the electronics board and the keyboard.
Two things could cause problems there: Corrosion or cracked screw posts. You can always try to remove corrosion if that's the problem, and there are several sources of information on how to repair cracked screw posts. I don't know about halfnuts - I have never opened one so far. I think they, too, can corrode, but the screw posts are no longer critical to the conection. Would make it a bit easier, then...
The problem is that these posts are extremely fragile and are easily damaged just by unscrewing the nuts. Therefore, I would first try again to fix the contact you already cleaned, between the battery/port assembly and the keyboard. Clean it again very carefully using very fine (1000 grit) sandpaper, then apply a contact spray to both the board and the felx circuit. Repeat if necessary. Hold the two halves togehter without inserting the screws and see if you can get the machine to life. Sometimes pressing on one side or the other or slightly moving the top half against the bottom suddenly produces a sign of life.
You should only dissassemble the lower contact if all of the above doesn't lead anywhere. And of course, make sure the problem is not the batteries ;-)
Tell me if this helps.