The Museum of HP Calculators

HP Forum Archive 18

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Message #1 Posted by Derek G. Graham on 1 Jan 2008, 3:55 p.m.

This is my first time on this message board so please take pity !

For the first time ever I have a "NULL" Message on my 41CX.

I cannot figure out how to get rid of it and get back to normal functions.

I have pushed all the buttons (and wiggled them too) but obviously not the correct one(s) or sequence(s).

I've tried to turn it off with the ON button but this does not work at all to shut it off.

Removing the battery clears the screen but on replacing the battery, the screen NULL message comes right back.

There is a program set by cards on the CX that can be re-loaded.

Any hints would be most greatfully received.

Thank you


Message #2 Posted by Karl Schneider on 1 Jan 2008, 4:30 p.m.,
in response to message #1 by Derek G. Graham

Derek --

"NULL" is the message displayed when a command is cancelled by holding its (last or only) key down for a few seconds. The message should disappear when the key is released.

Possibly, a persistent electrical contact is being made on one or more of the keys on your HP-41CX, due to mechanical failure or contamination.

One thing you could try is a master clear: Turn the calc on while holding down the backarrow (CLEAR) key.

If that doesn't help, I'd recommend inspection and repair by The site owner has repaired several of my own fullnut (pre-1985) HP-41's.

-- KS

Edited: 1 Jan 2008, 4:36 p.m.

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