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HP-41CV repair question - Printable Version

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HP-41CV repair question - Monte Dalrymple - 06-11-2019 07:51 PM

I am embarrassed to ask this, but here goes. I have a nice 41CV (non-working) that I got off of TAS. I would like to convert it to a CL, mainly because the serial number is only different by 35 from my original 41CV (now a CL).

I can't get it to turn on, even after cleaning/swapping everything. I looked at the supply current while pressing different keys and found that the ON key doesn't cause the slight increase in current that I see with other keys. The key action itself is nice, but the ohmmeter says that the resistance when pressed is over 200 ohms. The other keys that I looked at are under 10 ohms when pressed. So, it makes some amount of sense that the machine can't be turned on. But is there anything I can do to fix the key, beside the obvious "remove the heat stakes and replace the dome"? I have never done this and expect that I'll screw it up the first time I try it. I have tried injecting some DeOxit into the hole under the dome but that doesn't seem to have done anything. Or should I stop wasting my time?

I should point out that my current measurement tests were done with a known-good CL board installed.

RE: HP-41CV repair question - Jose Gonzalez Divasson - 06-11-2019 10:39 PM

Hi Monte,

I usually pass some drops of Caig DeOxit with a pin through the hole in the keyboard board, and then "remove around" with the pin. Then some exertions on the key, then repeat again.

Sometimes works well, sometimes doesn't

RE: HP-41CV repair question - Ken S - 06-11-2019 10:51 PM

If you have a card reader or wand you might want to see if they will turn the 41 on. I believe either trying to read barcode or a card will automatically turn on a 41. May be worth trying just to verify that the problem is with the on switch and otherwise the calculator is functioning correctly.