How to identify an HP-41C or CV?


I purchased a used 41-CV on eBay. I was fairly satisfied, but I think it is actually an HP-41C that someone mated to an HP-41CV upper half/keyboard. Or the main circuit board is from an HP-41C.

Unless I am really rusty, I should be able to execute
SIZE 070 since the CV should have 319 registers. I can only allocate 63 registers (00-62). If this is the case, I will return the calculator. The CV does not have a SIZE? command/instruction like the CX.

The serial number is 2326S40643, but I guess that doesn't mean very much.

Any advice? Am I missing something? It's been a few years since I used my other HP-41CX.


Assuming the calculator is totally clear (if not do an all-clear--turn the calc off, hold down ON and <- simultaneously, then release ON and quickly after back arrow--display should show MEMORY LOST) set SIZE 000. The press PRGM. Display should show 00 REG 319 for a CV. If it shows 00 REG 63, you have a C.



Thanks, I just cleared everything. According to my CX manual, the C and the CV default to 46 uncommitted registers that you will see when you press PROGRAM. However, the CV will then have registers 00-272 available which this calculator clearly does not have. My fake CV has R00-R16 available (46+17=63) which means it is a fake.


Try this just to be sure

272 STO 00
RCL IND (gold key) 00

If you get "nonexistent" and the calc is in the default state, you don't have a CV.




can you identify if yours is a halfnut or a fullnut? Please, see the picture below.

I have a halfnut HP41CV that behaves like an HP41C. The problem is that the halfnut models are not fully component serviceable, meaning they have too few components: the main processor and a hybrid IC, with memory (RAM/ROM) and display control. The halfnut HP41CX has an extra, small PCB, with the clock chip. The hybrid IC found in all halfnut HP41's is somehow equivalent to the Voyagers' R2D2, the RAM/ROM & Display Driver chip.

In my genuine halfnut 41CV, the upper RAM chips have gone bad, and the calculator allows maximun SIZE 063. In fact, the still working RAM chip is not good too, because either program or register contents mysteriously change, and the calculator freezes from time to time. In the fullnut models, chances are that replacing the RAM IC's will fix it. In the case it is a fulnut 41C, inserting the four extra RAM chips will give you a fully functional 41CV.

These RAM chips are not for sale (have never been), so you'd need a 'donator'. may be a starting point.

Best regards and success.

Luiz (Brazil)

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