HP41C to CX internal upgrade



I found my old HP41C in some drawer, and I've been amazed
by the quantity of documents and stuff on the web ! I want
it to be my calculator again.

I remember a very old french magazine having an article
on "How to upgrade 41C to 41CX by doing some electronics
inside the calculator, i.e. adding MEM and X modules BUT
leaving the four external ports free).

Has anyone some experience on doing this ? I remember that
41C was pretty low in memory, and I'd like to keep external
ports free for peripherals.

By the way, what is this "Advantage" pack ?

Thanks for any help


Personally, I'd just go and buy an HP41CX :-)

But, yes, it is possible to make a C into *almost* a CX by installing a quad memory, and X functions and a Time module internally. In fact you'd probably go the whole hog and fit two X Mem modules too.

But given the time and effort required, it would really be a labour of love rather than an economic decision (IMHO).


Hi Stephane,

You are French speaking, aren't you ? I'm locate din Belgium.

The advantage pack is an application pack with several maths and and other few functions.


C'mon guys! The obvious question to ask here is "what is the serial number of your "C"? I might trade you a CX for it!


Nah, I've already got one of those. :-)

(Insert geek info on serial numbers here)

Actually, I don't have a halfnut C, and my only opt 001 is a CV fullnut (from memory).

Any donations of calculators falling into the (numerous) gaps in my collection gratefully received!

Now, who was it that bought the 2 CV's with consecutive serial numbers on eBay recently?

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