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HP Forum Archive 12

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HP-41 CX
Message #1 Posted by Giancarlo Gentile on 15 Apr 2003, 7:07 p.m.

I have an HP 41 CX model and the display is malfunctioning. Does anybody know if its possible to fix it? HP here in Brasil tells me that, once this is an old model, they can´t fix it.


It is probably pretty simple
Message #2 Posted by Jeremy on 15 Apr 2003, 7:25 p.m.,
in response to message #1 by Giancarlo Gentile

It is probably just a matter of a dirty connection or something. That is usually what it is. I have never looked inside a 41, but if the display is modular as it is on the 32E I have just had apart, the contact between the LCD and the circuit board is made by a friction fit. Those types of contacts are more prone to malfunction by getting dirty that a soldered connection. On the other hand, if something goes wrong with a unit that has been designed in this manner, there is a better chance that it can be fixed.

If you have any technical skill in this area, you might want to take the machine apart and have a look. (There are instructions on how to do that linked from the homepage of this site.)


Re: HP-41 CX
Message #3 Posted by Vieira, Luiz C. (Brazil) on 15 Apr 2003, 9:34 p.m.,
in response to message #1 by Giancarlo Gentile

Hello, Giancarlo;

I met a Giancarlo at Universidade Católica de Petróplis in the late 80's. Would that be you?

The HP41 series has two basic types: the fullnuts and the halfnuts. Unfortunately I have no provider to hold my pictures anylonger so you could see a picture of them both. I'll send the picture to your e-mail if you wany. As a reference, please, take a look at your calculator's LCD and check if there is a black frame with rounded corners around the LCD's actual viewing area. If you see this black frame, yours is a halfnut-type. If the display has no frames and 90-degrees angles at the four corners, yours is a fullnut.

In the halfnut type, Jeremy's description is correct, but there is a big "hill" to climb: accessing the LCD's assy mean removing all (heat-molded) plastic rivets that lock the keyboard to the upper half-case, and the halfnut's LCD assembly contains not only the LCD's driver circuit, but also the ROM and RAM chips. Handling it demands extra caution and I have never disassembled a halfnut LCD... so far.

If yours is a (somewhat rare) fullnut HP41CX, LCD assembly is a separate module that is soldered in the keyboard and you may have just to resolder it. I can guide you in the second case.

Feel free contacting me if you want to carry on. As I live in Brazil too, we may arrange your HP41 maintenance here. (I have at least six different models in my workbench right now...)

Best regards.

Luiz C. Vieira - Brazil

(if you e-mail me, you can -surely- write in Portuguese...)

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