HP Advantage Pak problem

I have noticed that my HP 41CX won't turn on if I have my Advantage Pak inserted in the calculator. Can the Advantage Pak Rom be reset or is it worthless? Do these modules ever get fixed by fiddling with the contacts?




Try the pack in different slots. Also try cleaning the contacts with alcohol, mayby a swipe or two of 1000+ grit sandpaper, and slightly bend the contacts inwards.



silly questions, but...

1) have you tried in all four ports?
2) have you tried the pack in another calculator?

Sometimes you can fix this sort of misfunction by fiddling with the contacts, but you may also have a problem with the I/O ports themselves instead of the module.

The Advantage Pack is a big source of extra fuctionality. I hope you get yours fixed.

Best regards and success.

Luiz C. Vieira - Brazil


Thank you for your kind support. Alas, I tried all these things and it still comes up dead when the Advantage Pak module is installed in either of my two calculators. This happens in all the different ports and even after the contacts are cleaned and pushed out a little. Heavy sigh, I think this eprom is fried. I will just have to bury it next to my cat's grave in the flower garden...
Best Regards,

John Flinn



PLease, try it in another calculator. Also, (minimum) chances are you have a bad connection (cold soldering) inside the module, if it stoped working suddenly. I'd ask you to send it for me instead of bury it in the flower garden, but you'll spend nothing to send it to your flowers and Brazil is a bit far (and expensive) from your garden...

You may open it if you want, and opening a module needs some crefull maneuvers. It can be done, anyway. And you'll be a lot mad if this module get back to life by simply applying some solder in its intenal terminals.

Wanna try? Please, don't give it up. It worth spending some extra time to try to repair it.

Luiz C. Vieira - Brazil


Just to agree with Luiz, don't give up John, you've got nothing to lose, so go ahead: look for another calc, open the pack, check the solders... whatever... but please, please, please... do not bury (or throw trash, or burn...) the module.

Even in the worst case (if the ROM chip is "REALLY" burnt) the shell and connector are still valuable, sure you can make somebody near you very happy with them, so place an ad.

Best wishes from the Canary Islands.


Don't worry I wasn't going to bury it. I'll tape it on the back of a Brazilian Cerdo during the next Batucada performance in Eugene. That should get rid of any corrosion. Maybe one of those pyramids for sharpening razors would work. Is it hard to take the plastic case of the Application Pak?
Best- JF


Hello, John;

be caucious: depending on the rythm and energy, Batucada may get rid of corrosion, but may also shake information a bit inside the chip... if the module is back from the death and show strange behaviour, it's your sole responsability. ;-)

Back to actual life (thanks for the Brazilian reference; I mean it as a healthy call), one of our contributors in here has pictures showing how to do it by using a small knife. I cannot remember who has it, but I am almost sure it's not a North-American contributor. If I am wrong, please, forgive me.

If he reads these posts he will surely mention where are the pictures.

Best regards and good luck!

Luiz C. Vieira - Brazil

(I was confident you were kidding about throwing the module away; I was just trying to extend the joke a bit more... We take jokes quite seriously!)


Out of curiosity, how hard would it be to rebuild an Advantage Pak by burning new EPROMS? I.E., is the ROM easily replaceable with a readily available EPROM or FLASH part? Similarly, has anyone converted another module, such as a games module, to an Advantage or HPCC module by replacing the PROM? Of course, this presumes legal ownership of a non-functioning module containing the code to be burned



The HP memory chips were custom serial memories. Back in the before times, there were a couple of places that built a custom interface chip from the HP41 logic to standard parallel eproms and built them into programmable memory modules. Fat chance of finding one though. There is enough info floating around about the HP41 interface to duplicate the device using modern programmable logic, etc. but it is not an easy excercise.


After reading your response, I did a little search, and found this very interesting work-in-progress, which appears to implement a superset of the logic you mention. I imagine the FLASH ROM / SRAM emulator could be pared down to a simple ROM interface, perhaps with clock, etc., and fit in a small, inexpensive CPLD or FPGA; perhaps the data could be placed there as well, for low chip counts.


Oops. Here's the link:


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