HP41CV with missing registers


Hello everyone

I just received an HP-41CV that I won in an auction on that famous auction site. The calculator seems to be in excellent condition except that there is some corrosion in the battery terminals. Further, after installing the batteries I found out that in program mode it shows 46 registers instead of the 319 that you see when everything is okay. There are no programs stored in memory in case you are wondering, and when I installed the batteries the first thing I saw was the dreaded "Memory Lost" message.

My question is this. Is it possible that the corrosion is affecting the internal ram chips? Is that something that can be repaired by cleaning the corrosion with alcohol or some other chemical? I read somewhere after purchasing the calculator that corrosion can spread to other components internally. I wish I had read that article before hand. I will probably take it apart just to find out, but I want to know from someone that knows if that is the case. The calculator does not seem to have any broken posts since it is pretty snugg. My guess is that corrosion is the culprit please let me know if I am wrong.


What happens when you do SIZE 00? What does the register count in program mode show then? (Bear in mind that the number displayed on line 00 represents the number of registers available for programs; it does not include the number of registers currently allocated for data registers.)

- Thomas


I see Reg 319. Mystery solved. It is been a while since I used an HP-41 calculator. Now I remember that Size partitions program memory with storage registers. Thanks for your quick response. By the way, I opened up the calculator and saw that the corrosion is only in the two middle battery connectors. I did that because soon after I started using it, the calculator would not come back on. I found out that the inside is in perfect condition except for the corrosion in those two terminals. I used a couple of small pieces of aluminum foil to create a temporary fix. It seems that did the trick and the calculator now powers up, but the terminals need to be fixed permanently. I saw an article on the forum title "Repairing an HP-41CX" that describes such procedure, but I need to go purchase a couple of things like the glue and the brass strip to attend such a repair. Otherwise, the calculator is just better than what I expected to find.


Sometimes these battery connectors are offered on eBay. Another way to fix it was developed by Diego Diaz:

Replacement Flex PCB

Don't know if the replacement flex PCB is still available from Diego.

Good luck and enjoy your 41CV,



Thanks for the info. I will give it a try.

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