HP-41CVs will not turn on


So I have rebuilt and cleaned two Fullnut CVs in recent days.

Both are exhibiting behavior that is documented on the Museum, but I thought I'd ask again as I cannot seem to find the solution in the posts.

Steve's Post

One calc behaves as such:

Once on, will turn off normally with on button. No matter how many times I press on by itself, the display will not come on. However, if after turning off, I press on ONCE and then press BACKSPACE, ENTER, ON the calculator will ALWAYS come on. If I try that sequence after turning off, it will not turn on. If I do that sequence twice, it will turn on.

I cannot get the calculator to reset via BACKSPACE, ON

Once the calculator is on, it seems to work fine.



Lastly, I had similar problems with a halfnut HP41CX.

Eventually, all problems were resolved with a reset. A simple achievement of MEMORY LOST in the display did not help.
Try this link.


Short the 470 uf cap on the processor to reset the unit to all defaults. If the problem persists, my guess would be a bad rom or D/S IC. Swap processor board to verify. If it is a bad board, it would be almost impossible to troubleshoot without a service rom.

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