HP 41C Repair

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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Kindle and paperback versions available now!

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

- Corroded battery contacts

- Broken upper back case screw head supports

- Broken upper screw posts

- Broken lower screw posts

- Corroded or broken zebra contacts

- Corroded circuit paths

- Damaged screen - black spots

- Damaged screen - not all segments light on

- Dirty screen

- Damaged plastic protection

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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Zebra + Lower post Product no.: zebra+lowerpost Set of zebra + lower post repair piece 26.00 € * Old price 41.00 € In stock (4) Compare	Assembled HP-41c battery bay and expansion ports module Product no.: Flex-PCB Assembled Assembled module for the often damaged flexible PCB in the battery bay (and I/O ports) of the HP-41c range of calculators. Shipping included in price for EU customers. New price: cheaper circuit translating to 10% lower price! 55.00 € * In stock can be shipped within 10 days (43) Compare	Assembled HP-41c battery bay and expansion ports module Flat Product no.: Flex-PCB AssembledFlat Assembled module for the often damaged flexible PCB in the battery bay (and I/O ports) of the HP-41c range of calculators. Shipping included in price for EU customers. This is the FLAT version, when the screw head domes are broken and grinded down - see pictures. New price: cheaper circuit translating to 10% lower price! 55.00 € * In stock Compare
New Zebra connector for HP41C repair Product no.: Zebra PCB This piece is for repair of HP41c full nut calculator, substituting the damaged or corroded zebra connector that links the main board with the processor circuit. New design. 16.00 € * In stock (9) Compare	New Repair kit for HP-41c battery bay and expansion ports Product no.: Flex-PCB Adhesive circuit for the often damaged flexible PCB in the battery bay (and I/O ports) of the HP-41c range of calculators. Shipping included in price. 26.00 € * In stock (36) Compare	Spacer set for repairing old HP41c Product no.: SpacerSet Set of 8 pairs of spacers for nut-screwed full-nut HP41c calculators. Substitutes the nuts that are screwed on the lower posts to secure the circuit, 10.00 € * In stock (2) Compare
lower post long screw - inox Product no.: lowerscrew Two long screw for the lower screw posts of HP41c calculators 1.00 € / 2 piece(s) * In stock (1) Compare	lower post long screw - black pair Product no.: lowerscrewblack Two long screw for the lower screw posts of HP41c calculators - black 4.00 € / 2 piece(s) * In stock Compare	New Set of 4 screw for HP41 - inox Product no.: Screwset Two long screw for the lower screw posts of HP41c calculators + two long screws for upper posts. 3.00 € / 4 piece(s) * In stock (4) Compare
4 x Piece for repair of back case of HP41C Product no.: brokenback4 4 pieces for repairing HP41c back cases. This piece is for repair of HP41c back halves, specifically the support of the upper screw heads that is often damaged, and very difficult to repair in a lasting way. 50.00 € * Old price 72.00 € (2) Compare	New HP41c Lower Post Repair Kit Product no.: Lower Post Repair Kit Set of pieces needed to repair successfully the lower posts of HP41C, 41CV and 41CX full nut calculators, including zebra connectors, lower post part, and keyboard support for clothes' pegs to protect the keyboard 40.00 € * Old price 70.00 € In stock (4) Compare	HP41c battery holder spring Product no.: Spring Stainless steel 304 springs for HP41C battery holder 3.00 € * In stock (11) Compare
Piece for repair of back case of HP41C Product no.: brokenback 1 Piece for repairing HP41c back cases. This piece is for repair of HP41c back halves, specifically the support of the upper screw heads that is often damaged, and very difficult to repair in a lasting way. 17.00 € * (10) Compare	New Lower Post Repair part Product no.: Lowpostrepair Piece to repair HP41c full nut series lower screw posts 16.00 € * In stock (11) Compare	New Upper Post Repair part Product no.: UpperPostRepair Piece to repair HP41c series upper screw posts (tested with both fullnut and halfnut versions) 16.00 € * Still in stock (7) Compare
Keyboard support for repairs Product no.: keyboard support Piece required for the lower post repair of HP41c calculators. 25.00 € * In stock (1) Compare	New zebra connector holder Product no.: zebraholder Zebra Holder to keep the elastomeric zebra connectors in the contacts between main board and processor circuit in the HP41c calculator family, full nut versions. 12.00 € * Compare	Repaired HP41c back side Product no.: HP41Cback Repaired back side of HP41c. It can be used in case the original backside has the screw supports broken. 40.00 € * (1) Compare
HP41C/CV/CX repair Product no.: 41cRepair 50.00 € * (17) Compare	Card reader repair Product no.: card reader repair Card reader repair 60.00 € * (3) Compare	Card reader side-locks Product no.: cardreader sidelocks 3D printed HP82104A card reader side-locks - set of left and right locks 25.00 € / 2 piece(s) * In stock (1) Compare