HP-41CVs will not turn on



#4

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.

HELP!?


#5

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.

#6

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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