What have I done to my HP-41CX?


Help! I seem to have destroyed my 41CX after 14 years of TLC!

I had an IR module, an Advantage pac and an Extended I/O module plugged into three of the ports, and then plugged an HP-IL module with the printer enable switch set to ON into the fourth. I turned the calculator on, 0.0000 was displayed as expected, but none of the keys would work, include the on-off rocker. Suspecting that there was a clash between the IR module and the printer element of the HP-IL module I set the printer enable switch to off. I could then turn the calculator off. I removed all the modules and tried to turn the calculator on again, but nothing happened. I've tried resetting it every which way but to no avail (on-clx, shorting the battery contacts, etc.)

Some questions:
Have I lost my friend for good?
If not, what should I try next?
Why should doing what I did have such a dramatic effect?

Any messages of condolence would be gratefully received.



i did something very similar to this about 9 years ago to my first 41. it only had a surveying chip and an I.L. in it and i wiggled the I.L. while it was printing. the results were similar to what you are seeing if i remember right. i tried what you did plus shorting the circut board with a piece of aluminum foil and letting it sit without batteries for four days. all to no avail. i bought a used 41 to use. i then took out the batteries & did the foil gig to my wounded baby and let it sit for six months. when i put the batteries back in; it didn't quite forgive me right away. it talked conji to me no matter what button i pushed. after about two dozen strokes of the back arrow key i started to get numbers among the chinese symbols and eventualy it gave me "0.0000". it still rides in my vest pocket and every day gives me good answers - along with the time and date. so i'm not giving any condonences about yours till i see it's bones. good luck.


Upon 'sudden death' of my HP41's I just short-circuit the battery terminal inside the calc (after taking out the batteries of course) with some (copper) wire while at the same time rocking the on-off switch. For the very stubborn machines I short circuit and push the reset sequence at the same time. Seems to work every time. No guarantees though.

The alternative of taking out the batteries and waiting forever somehow did not appeal to me.....

Good luck reviving !


Ok, only the WHY :-)

The IR printer and the HP-IL with the printer enabled both contain rom at the same location. The calculator gets quite upset with this.

I did this a while ago and my calculator just did a MEMORY LOST to me.

If your's hasn't done a memory lost yet, then may I suggest the following:

1) take the batteries out, and replace them. Sometimes this is enough.

2) the newer HP41s have a reset somewhat similar to the ON/CLX that forces a memory lost. press CLX, and enter, then press ON. Note that this works only for calculators made after mid 82 (serial 2234xxxxxxx or later?)

otherwise... shorting the battery contacts is a good suggestion.

Be very careful with ROMs that map to the same memory space. Especially the Printer, IR Printer, and HP-IL.


My 41CX is a halfnut made in '86. I will try the reset sequence you suggest.

By the way, in case I am doing it wrong, would someone please take me through the battery contact shorting process.

Many thanks.


In the book Exteny your HP41, section 4.1, a number of methods are given to revive a calculator that won't turn on.

OK, yours turns on, but it's unresponsive.

1) press backarrow and/or shift to see if the blank display is caused by alpha blanks in the X register

2) press on then backarrow, then on, then backarrow a few times, pausing about 10 seconds between keystrokes

3) remove all modules and try again (there's also mention of the use of an AM radio here too, as well as chacking for dirty battery terminals, flat batteries, and incorrectly inserted batteries)

4) IF YOU HAVE A NEWER HP41, try pressing backarrow and enter then on, then releasing all three

5) if you have a wand try reading some barcode

6) try pressing R/S

7) attatch a card reader and run a card through it

8) take out battery and reinsert. then press ON a few times

9) obscure

10) memory lost (aaagh!)

11) take out batteries for a LONG time OR insert batteries the wrong way (using old batteries) (POOR ADVICE IN MY BOOKS) OR short the battery terminals (place wire or foil over the gold connectors. It's the outsoide two that you need to short, but you can connect all of them without any problems)

12) really nasty

13) even worse

I used to have a card with an autoexecute program on it. The program was simply STO c. That worked for me once too. It is actually mentioned in step 10 in this book too.

Good luck.


Multiple CLX-ENTER-ONs, followed by multiple battery contact shortings did the trick!!!

Many thanks to all of you who responded with such useful advice.



glad you got it up - so to speak. but i'm equaly glad that i didn't know this trick then; or i would not have bought my spare.

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