Re: HP41C Message #5 Posted by Tony Duell (UK) on 2 Nov 2001, 1:55 p.m., in response to message #1 by Paul Vollbracht
Yes, there is a DC-DC converter _in the card reader_. I am not sure what the output voltage is, but even if it's failed, the rest of the machine should work.
I would start by trying to fix the 41C on its own (without any peripherals or modules plugged in). Then, when that works, fix the add-ons, if they need fixing.
OK, most problems with HP41s are bad contacts inside. Take the machine apart (4 screws under the feet), lift off the back cover, undo the nuts holding the logic PCB in place (if present), remove the logic PCB and its connector.
Clean the contact pads on the logic PCB and keyboard PCB. Clean the logic PCB connector. Clean the flexible PCB contacts on the I/O assembly inside the lower case. Squeeze the sides of the flexible PCB at the keyboard connector area to improve the contact there.
Propan-2-ol (isopropyl alcohol) is about the best stuff to use for cleaning these parts. Then put it all back together. Most likely it'll work again.
Sometimes an old rechargeable pack will leak and damage the flexible PCB. It's possible to carefully solder wires across the damage, but it's not easy to do this. It's better to look arouns for a 'parts unit' with a good I/O assembly.
Of course the HP41 is almost entirely CMOS logic, so you must take anti-static precautions (ground yourself with a wrist strap, and so on). You don't want to damage the ICs.
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