HP41CV faulty


Hi folks - new to the forum so please go easy with a "newbie".

I have an HP41CV (Fullnut I think you call it) which has seen better days - badly corroded battery terminals, and intermittent contact between the logic board and keyboard. Rather than scrap it, I pulled it to pieces and hard-wired the logic board to the keyboard. Temporarily I've connected a 6v supply directly across the appropriate keyboard traces.

It doesn't work! Here are the symptoms:

At power-up the display shows the "flying duck" in the leftmost display position and the PGRM annunciator is on. None of the keys has any effect except:

* Pressing the ON key causes the display to briefly show "MEMORY LOST" and the beep to sound before going back to the original display.

* Pressing R/S changes the display to "0," at the left and "00" at the right. Pressing R/S again puts it back to the original display.

Before throwing it in the bin I wondered if those symptoms give any pointers to what the fault might be.

I've very carefully check my hard-wiring of the logic board to the keyboard - everything looks correct with no shorts.

Grateful for any help,


Anytime a 41 displays MEMORY LOST at power on (other than after a complete reset of memory) is usually a sign of a bad rom or ram.

Realistically, the only way to troubleshoot is with the HP 41 service rom.


Thanks Randy - looks like it's on its way to the bin!



Do NOT throw it!

If it has a good keyboard and LCD, it can probably be salvaged and converted to a 41CL by replacing the logic board.

At worst, it will most likely have some use for spare parts!


Yes - the "bin" in question is the spare parts bin ;) I have 3 other HP41s, so it might come in useful at some stage.

Next job is to replace the "crumbling" drive wheel on my card reader!

Thanks for the advice,


How can I do it? How "transform" my HP-41CV into a HP-41CL? regards...


Hi dinamarco,

Checkout this 41CL Link . You will find all the necessary information about the 41CL upgrade. Also checkout this for further information.41CL wiki link
Regards, Kerem

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