Repair for HP 41CX


Hi, can anyone tell me where I can get repairs on my HP 41CX. Needs professional care. Thanks



If you need HP repairs, unfortunatelly they no longer support this model. Otherwise, depending on what is happening with your calculator, chances are it can be repaired by some guys in here (me included, just in case...). As you have an hP41CX, it depends much on the model type, either.

Would you briefly describe the problem? Also, please, have a look at the display (LCD) and check if it has sharp, clear, 90º corners or if it has a thin black frame with rounded edges. This will help us to identify if your calculator may be or not repaired, depending on the problem.

Best regards and success!

Luiz C. Vieira - Brazil


Someone gave me a dead one, but this is a HP-41C model instead. I can't get it to work.

- It just switched ON and then shuts down immediately
(batteries brand new & connectors very cleaned).

- Which are the differences between the models with the 90o corners (LCD display) and those with the round ones ?

Mine (s/n 2015A01973) with the square corner LCD display.

Many thanks,


The older (square cornered) module (the fullnut) has a removeable CPU card and display module. They are much more repairable than the newew models (but less reliable, becuase they have more internal parts and conenctions to go wrong).


Hello, Pyerre;

There two types of 41's, and they are recognized by the LCD's window. Have a look at yours and check for their corners: are they clear, sharp 90º edges? If so, yours is a so called fullnut, an earlier design, and this type has a "secondary" board (in fact, the mainboard) inside it with all chips and electronics components built on it, except for the LCD's drivers, that are built in the LCD's assy.

If the LCD has an extra thin black frame (internal) with rounded edges, then you have a halfnut type. This type has newer design and uses SMT (Surface Mounting Technology) components. There is one PQPF (Plastic Quad Package - Flat) CPU built in the keyboard and the other chips are built in the LCD assembly (RAM, ROM and Display Driver - one could call it an R2D2, but this is the designation given to the Voyagers' CPU).

The halfnuts are harder to repair, but they tend to be more reliable (some users do not like their key-"feeling"), and I tell you that I have one HP41CX and one HP41CV halfnut (newer design) and one HP41CV fullnut (earlier design). The fullnut has some problems regarding bad contact between the mainboard and the keyboard, one of the most symptomatic parts of the calculator. If this contacts are bad, the calculator fails often. I have opened many, many fullnuts, but I opened just a few halfnuts. Maybe others have different experiences. My both halfnuts were opened no more than 8 times, counting both of them. In all cases, there was a problem of bad contact between the BAT/IO assembly and the mainboard. Just cleaning. But the fullnuts have three contact sets to be periodically checked, and two of them are under the mainboard.

I think that's all. If you believe you need to, there is no big deal opening the HP41 fullnut. Check the LCD's corners and let us know.


Luiz C. Vieira


Many thanks for the informations.
This HP-41C has the clear, sharp 90º edges LCD display (like
this : So called the fullnut one.

Never opened one before, I'll try to do it per instructions
& hope to wake it up again. Scaring huh!

Many thanks once again, Pyerre

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