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HP41CX doesn't turn on - Printable Version

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HP41CX doesn't turn on - Ralph - 01-22-2005


I own a HP41CX I bought three years ago and since then it has always functioned correctly. I haven't used it on the last year so I removed the non-rechargeable batteries to prevent from corrosion and stored the calculator on a safe place. Yesterday I picked it up again and placed the old batteries and turned it on. It showed the MEMORY LOST message for about half a second and then the message faded and the calculator seem to be DEAD! I've replaced the old batteries with new ones, but the same: after placing them I turn it on and it shows the message and then fades and nothing more happens.

Has someone an idea what could be wrong? I hope the calculator is not damaged of being not used!

Thanks for the help

Re: HP41CX doesn't turn on - Ralph - 01-22-2005

I've been reading a bit on the MoHPC article about batteries and says for the 41CX they must be N cells. I've looked at the ones I bought: The model is VARTA 4001 . LR 1 Alkaline (1.5 V). Now I'm not sure if they are the right ones for the calculator...the size of them is correct, however.


Re: HP41CX doesn't turn on - Vieira, Luiz C. (Brazil) - 01-22-2005

Hi, Ralph;

I own five working HP41, one of them (HP41C) is with me since it was bought new in the beginning of the 80's. All I can tell you is that I experienced some cases like this, where you insert batteries and they momentarily charge the capacitor built in parallel with them. Because of bad contact (battery holder springs with residual corrosion, batteries main contact set, even contacts between IO/Batt assembly and mainboard...), the batteries do not feed the mainboard circuitry after they are in place, so the remaining charge in the capacitor is enough to power the calculator up time enough for you to see MEMORY LOST message fadding. In all cases, I cleanned each part I mentioned above, same sequence, and tested the calculator. I don't recall any unsuccessful attempt. In two or thee cases I had to reduce the spring pressure by "deforming" them slightly; some springs force the IO/Batt assembly too much when and after the bettries compartment is inserted.

If you need to open the calculator there are some helpfull hints here, but I'd try some "external" cleanning mostly if you have not done this before.

Let us knwo what happens next.


Luiz (Brazil)

Re: HP41CX doesn't turn on - Ralph - 01-22-2005

Hi Luiz,

I have repaired it. I've clean all contacts and have observed the springs that hold the batteries make a great force. So I have put the battery holder in place but just pressing it so that all four batteries made contact. I've then turn the calculator on and it worked fine (nice to see the 0.0000 again). The solution has been deforming the springs a bit so that they don't press with too much force. So easy!!

Thanks very much for the help!

I'm glad you made it! (NT) - Vieira, Luiz C. (Brazil) - 01-22-2005

Re: HP41CX doesn't turn on - Stefan Hauschild - 01-23-2005

Your battery type is ok - I use the same ones. And I have discovered that the battery holder of older HP41 is somewhat tricky to insert. On my two HP41s I have to adjust it smoothly every time I change batteries. Even after cleaning all contacts with a fiber pencil eraser it has to get the correct pressure on all contacts.
It seems to be the same problem with your calculator.

Best regards


Re: HP41CX doesn't turn on - Ralph - 01-23-2005

Before that I had only changed batteries on my HP-41 once, but now I'm getting familiar with the holder, as you say if it doesn't makes the correct pressure the calculator won't turn on.

Thanks for the counsel.