HP-41 Squeal

Put in a fresh battery pack, press ON, HP-41CX squeals, a high-pitched whine. No intelligence on the display. Pressing some keys makes the whine louder, some make it softer. Any suggestions on how to reset this baby so she powers up? Thanks in advance. For the record it's a fullnut, serial number 24xxx....


it seems to be normal for a 41 to utter a small chirp of happiness when you slip in a set of batteries after a long period of non-use. this sounds more like "deliverance". i would check your battery polairity just to be sure, then cross the terminals on the 41 and leave it for about three days with no power. there may be some accidental partial program sequence in memory that is causing the noise and that will clear it out. synthetic programming can make a lot of tones and all synthetic is is a fortuitous string of steps that hp did not expect to go together - but do. if that dosn't work maybe you should send it to dr. mike. this could be a deep seated phobia of 6 vdc and require years of analysis.


Installed the PPC ROM, managed to get the calculator to wake up by pressing lots of random keys while holding the ON switch. But when it woke up it was in some bizarre "2 _ _" mode with a bunch of random flags set and the radix set to "," that I could not clear with a master reset. So I just ran the 'CX' (curtain to absolute location in X) program in the PPC ROM, which I recalled from 20 years ago was one of those programs you just NEVER ran because it caused an almost immediate MEMORY LOST. Well I'm happy to report that the 'CX' program still works as advertised, even after 22 years. Got a cheerful MEMORY LOST and now all seems to be working fine. Thanks. -mark.


Hi, Mark;

some months ago I passed some scary moments with my halfnut HP41CX. After experiencing a bad-contact behavior, it got into a "snooze" condition like yours: a high-frequency pitch, frozen keyboard, meaningless display. I readonce that removing the time module may "cure", but tell me: how to remove a time module... from an HP41CX?

I opened the calculator and simply shorten two capacitors inside it. One of them - the bigger one - seems to be in parallel with batteries (DC line) and the other... well, the h...! I shorten both and closed the calculator again. It was enough to put fresh batteries and see the so expected [MEMORY LOST ], sometime you hae it, sometimes you live, isn't it true?

As you have already been successful, I'm glad anyway.

Best regards.

Luiz C. Vieira - Brazil

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