HP 41C Repair
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New book from The Calculator Store: HP41 Repair: A Beginner's Guide to Repairing your HP41 Calculator. 14.00€ paperback version, 9.99 Kindle version. Only in Amazon
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The HP 41c family of calculators started being produced at the end of 1979 and lasted in its last versions until 1991. Such production time span attests its quality and advantages for the work of engineers and scientists. Many of you had a HP41c at its day, or lusted for one and you've given yourself that gift. But one day you pick it up from the drawer, or it falls to the ground, and it doesn't work anymore. What do you do?
Repair it!
We are fanatics of the HP calculators, and the HP41c occupies a warm place in our heart. We have repaired many of them, and we think that we have seen most of the problems that these machines have. We do not claim to have found the solution for every problem, but we have for most of them.
The first HP calculators were very solid and well designed. The body was independent of the circuits, and the screws that secured the circuit were not required to hold the machine together too. This resulted in more robust calculators. The HP41c, with all its technical advances, was not as well designed as the calculators that preceded it (with the exception of the Spice series, which was a true desing flop). We have identified several weaknesses that appear again and again, and we have found solutions for them. Click on each problem to go to the respective page.
Types of failures
How to determine what is your problem? Beware - you may have to disassemble your calculator!
Corrosion on the contacts is very easy to spot. You can see the battery contacts corroded. It is usually the leftmost contact which gets corroded first. This is the lowest potential point ("-" contact)
Broken upper back case screw head supports: you can see both halves of the case are loose in the upper part of the calculator. This impedes power transfer from the battery to the circuit. If you take the upper rubber feet out with a small flat screwdriver, taking care of taking the adhesive sheet with it, you see the screws below. You will be able to see that they are "free" in this case. If they are not free, the the problem may be the broken upper repair posts - and you'll need to disassemble the calculator to see it.
Broken lower screw posts: the lower part of the calculator seems loose, and it may happen that it works when applying pressure to the lower part of the calculator keyboard (around keys 1, 2 and 3)
Corroded or broken zebra contacts: you can only see it if you open the calculator. Indicators of this problem may be missing digits or segments in the screen, or the calculator not working.
Corroded circuit paths: you can only see it if you open the calculator. Usually happens with battery contact corrosion - never comes alone!
Damaged screen: in all cases disassembly is required.
- black spots: seen in the screen. You can only change the screen (soldering required!)
- not all segments lit: it can be the connections to the screen, the lower zebra corroded, the lower screw posts broken, etc.
Dirty screen: you can try with pressured air through the side openings, and if it doesn't work you will have to unsolder the screen.
Damaged plastic protection: complicated! sometimes the damaged plastic protection is easy to take off the machine; you need to disassemble and unsolder the screen; if it doesn't separate easily, we have not found yet a way to repair it.
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Módulo conector de baterías y puertos de expansión de HP-41c/cv/cx
N.º de producto: Flex-PCB Assembled -
Módulo conector de baterías y puertos de expansión de HP-41c/cv/cx Plano
N.º de producto: Flex-PCB AssembledFlat -
Conector zebra para la reparación del las HP41c full nut Nuevo
N.º de producto: Zebra PCB -
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