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Recently, I aquired an HP-41C. At first glance, it seemed to be a normal one. But during function testing, I noticed that it had 319 memory registers. I also discovered that it understood the Time Module commands!

Well, I guess you understand that I had to open the calc. And that's what I've found:

Enhanced HP-41C

A thin PCB (green) is connected to the extension port contacts on the 41 PCB. The 4 memory modules are soldered onto the green PCB, near the border of the case so they perfectly fit into the upper part of the case. The time module is also connected to the green PCB by thin wires.

The green PCB is labeled with:




Does anybody know some details about this BERNYTRONIX thing? Or does anybody know of similar HP-41C modifications?

Regards, Juergen

Hello Luiz,

This arrangement could let the expansion ports free? Great work!

Hi, Artur;

I guess it would, because if we consider that this is what we (should) have in an HP41CV, then the addresses are consistent and there are no conflicts.

At least, this is what I guess.



If you want to know see the PCC Calculator Journal, Volume 8, No 1. for an article (with diagrams) explaining how to dissemble a memory module and wire it into a HP41C. It explains circuit board contacts for the port bus and the hardwire mapping for memory modules.

The article shows using wire-wrap wire but apparently in your case some enterprising user(s)developed a circuit board.

It was possible to stuff 4-6 bare modules into the 41. Standard memory modules (single or Quad), Time, X-Functions,and X-memory modules were the usual candidates.

With a Quad Memory, Time, X-Functions/X-memory and two X-memory modules you had the equivalent of a 41CX with the full amount of X-memory registers added. The only thing lacking were the extra functions in the Xfunctions of a CX. And at the time of the article I don't even think HP was selling the CV never mind the CX.


thank you much for this background information and the PPC reference. I'm sure I will enjoy reading the article!

Regards, Juergen