HP 41C


Dear Sirs;
I couldn't get any info from Hewlett-Packard.
I have a HP41C that the "3", "6" and "9" keys function like the "x", "+" and "-" keys. Can the 3, 6 and 9 keys be "re-learned" ?




just to start the engines: is there a USER annunciator lit at the LCD´s down-left corner? If so, press the USER key and it must be turned off. Try the keys, now.

I would write a few words about USER keyboard, USER mode and flag 27, but I will wait for the next post.

If there is no USER annunciator lit, there is a real problem in the calculator I can´t figure out now.



The USER annunciator is lit. Keys do the same, User on or off.



I do not have my old HP41 (guts exposed) in hands now, but I believe a short circuit between two tracks of the keyboard could cause this abnormal operation. I´ll be home later today and I'm posting again, if needed (maybe Mr. Duel -UK- will read this post soon and answer with a better explanation OR a ready-to-use solution; I hope so).

I have removed the keyboard of three 41´s (fullnut) and one of them did not work properly: some keys caused no reaction. Battery leakage was the main cause.

In your particular case, the misplaced keys are in the same row of their "mask" keys. This suggests me that a short circuit is causing all this mass.

I´ll post something later.


Besides a short circuit on the keyboard, it could be a fault in one of the zebra connectors between the keyboard and CPU card (assuming you have a fullnut HP41). These connectors are designed to conduct electricity vertically but inhibit its flow horizontally. If you have a problem in the connector it can cause two adjacent pins to short together.

Whenever you take apart an HP41 you should always clean these connections. You might try rotating the zebra connector 180 degrees and see if the problem goes away or changes.



always learning! Thanks for the valuable tip.


Forum Jump: