HP-41CV Doesn't go into PRGM or USER mode


Hello all.

I just got a new 41CV off of eBay. I just installed new batteries. I presume the memory contents are gone by now because the 41 shipped without any power. Funny thing though, all the keys work, I can turn the 41 on, put it in ALPHA mode but, I cannot put it in PRGM or USER mode. Please advise.


I tried a test:

I copied the Games Module program, 'Subhunt' into program memory and ran it. The USER annunciator lights up and the program operates. I just cannot enter PRGM mode or toggle USER mode.

Edited: 15 Mar 2012, 12:07 a.m.



Your HP-41CV trouble seems to be just the keyboard.

You can set USER mode from a running program or from the keyboard just setting flag 27.

PRGM mode flag 52 is not accessible by simple keystrokes though.

It's possible that some dirtiness has found its path inside these two keys and prevents proper contact from happening when depressed.

Cleaning will involve taking your calculator apart, using a thin brush damped in isopropyl alcohol and inserting it trhu the vent hole in the keyboard PCB under the key.

If it doesn't make any difference, you may need to use a small piece of wire instead said brush to effectively remove any residue from the contact area.

A good dose of patience is highly recommended.

Hope this helps



Edited: 15 Mar 2012, 6:32 a.m.


Hello there. Thanks! I think I'll leave that cleaning job to the professionals. So, when I'm ready and if someone here can fix that, I'll send it over. Or should I just send it to FixThatCalc?

Edited: 15 Mar 2012, 1:47 p.m.


For the moment FixThatCalc is in technical "pause".

More info in its web page: Here.

Hope you get your 41 back to life soon.




Yah, I saw that hiatus bit on FTC's website but, it says the place should be back up in a couple of weeks or so. Plus, they've got a huge backlog. Nevertheless, I can wait because the backup 41 I ordered off of eBay a few days ago came today. And, it's fully functional!

So, I'll send the fishy one to FTC when they come back from under the workload.

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