I have an HP-41C (made in 1980) which was working perfect and suddenly it turned off by itself. Now I can´t turn it on. Somebody said me it could be static charge. I put the 4 batteries out and waited 24 hr, but it doesn´t work.

Does anybody know what to do???

Thanks in advance



Hello, Jon;

based on a few experience dealling with HP41 (I have four working models with me) I'd tell you first: don't panic!

Now let's see. Chances are you have a simple problem of bad connection (bad contact) between the BAT/IO assy (batteries and the I/O port connections and assembled in one single piece) and the keyboard. This is normally due to oxidation from battery leakage.

You can check it by removing the batteries again and looking carefully at the batteries contacts. Can you see any green power that would smear in your fingers? This is the sort of oxidation that may form under the batteries' contacts. Sometimes you can see it, sometimes its hidden under the black plastic in the bottom of the batteries compartment that surrounds the BAT/IO assy contacts.

Do you have the skills to open it and try to clean it? It seems to me yours is a fullnut. Please, check for it based on the image below.

Let us know if you are willing to open it or not.


Luiz C. Vieira - Brazil


Thank you for your fast answer:

It is a "fullnut".
I have opened it (removing the four screws under the feet)and I can´t see any oxidation. It looks very clean. I have used a voltimeter and I read 6.2 V in the plastic connector. So it seems the battery contacts are ok.
I can´t see any broken plastic in the screw holes (I don´t know the word in english) so I think it closes ok and the contact should be right.I haven´t dissasembled any more. After assembling again it doesn´t work.

What else can I do??

Thanks again



please, downlaod this PDF file and check for the two first pictures showing the HP41 opened. There is a zebra connctor that allows the electrical connection between the "mainboard" and the keyboard. You should check this zebra connector carefully, because there is one type of them that has very thin golden-plated cooper trails. Also you should try to use plastic washers (thin ones) between the mainboard and the back cover to ensure there is preassure enough over the contacts.

These are the most common problems and correcting procedures. I hope you have success. If not, post again.

Best regards.

Luiz C. Vieira - Brazil


Here is one more thing to check if your calculator doesn't turn on. If the coil springs in your battery pak are tired, sometimes there is not a good contact. Try stretching them a bit so that they give better pressure on the batteries. Another thing, if you take out the batteries for a couple of days, sometimes the calculator resets itself. I have a 41CX and I got it to work after removing a dead Advantage Pak module, stretching the coil springs and snugging up the tiny screws under the rubber foot pads.

Hope this helps!



I have dissasembled the main board and the zebra connector is clean. I have checked all the contacts and they are ok. In fact all the calculator´s inside is perfect (clean, without any corrosion). And after assembling everything again I have found out the problem: battery contacts don´t work properly. The previous owner painted them with silver paint (conductive). It has very good aspect but it seems to lose conductivity due to batteries friction. I have a photo but I don´t know how to attach it

If I place silver paper in each battery contact the calculator works again
Now I know the problem but not the best solution. Does anybody have experience solving this failure.

Thanks in advance




there are self-adhesive cooper foil from Chomerics (it seems to me the e-address is and I think they're the best solution. It is not golden plated, but it has conductive glue and you can cut it and apply directly over the battery contacts.If you look carefully, there is some part of the contactcs in the calculator's BATT/IO assy that are exposed, so you can even solder the foil (low-temperature soldering iron).

At the Chomerics site you may request a sampla, that will be enough for your needs.

Best ergards and success.

Luiz C. Vieira - Brazil


You can try more silver paint. I don't know if you can still solder to the contacts, but if so I use small pieces or brass "U" channel strip available at most hobby shops. Cut a small piece of the brass strip a little shorter than the battery contact. Clean and sand lightly inside the brass piece. I run a small bead of solder on the battery contact, a small bead inside the brass channel, place the brass over the battery contact, heat from the top to melt the two solder beads together. Voila, a very heavy duty battery contact.


Thank you to everybody:

I will try first the self adhesive copper foil. But it is interesting to know that I can even solder it.

Thanks again


Possibly Related Threads…
Thread Author Replies Views Last Post
  HP Prime Save Power Turn Off Not Working Timothy Roche 12 4,183 10-27-2013, 01:41 PM
Last Post: Michael de Estrada
  Temporary User Mode Key Programs not working in RPN BruceTTT 7 2,723 10-14-2013, 01:46 PM
Last Post: BruceTTT
  HP-97 suddenly not working Brad Barton 10 2,821 02-25-2013, 08:15 PM
Last Post: Brad Barton
  [41CL] Problem with PowerCL ... not working Doug (NYC) 5 1,998 01-22-2013, 07:18 PM
Last Post: Doug (NYC)
  42S exit key not working dwsmith 4 1,682 11-05-2012, 10:59 AM
Last Post: dwsmith
  HP-46 not working Ignacio Sánchez 1 1,030 10-24-2012, 11:17 AM
Last Post: Donald Williams
  [WP34s] last QtGui version not working fhub 8 2,512 08-31-2012, 05:08 PM
Last Post: fhub
  Modfile not working with Win 7 x64 Richard Wagoner 6 2,283 07-04-2012, 10:32 PM
Last Post: Diego Diaz.
  Working on HP's again Les Koller 49 13,037 06-20-2012, 01:29 AM
Last Post: Thomas Radtke
  held breath, found tapes & drive working Garth Wilson 9 3,144 06-12-2012, 12:52 AM
Last Post: Garth Wilson

Forum Jump: