HP 41CV freezes on pressing ALPHA


Dear Experts,

I have acquired a HP41 CV from eb**. It looks okay, and I can
calculate with it and write little programs, but each time
I press ALPHA the display goes blank (except for the ALPHA annunciator) and freezes. Entering letters or digits is not possible.
If I press (ON-Backspace) or (ON-Enter) it goes back to the 'normal' mode and displays the last stack allright.
Several tries with MEMORY LOST/battery removals did not change this.

Has anyone of you seen this? Is there a possibility to fix this or should I just forget about the machine and buy another one?

Thanks for any hints,


Martin --

Is the HP-41CV a fullnut (1980-1984, rectangular display window), or a halfnut (1985-1990, window with rounded corners)?

If it's a fullnut, it may benefit from an ultrasonic cleaning and re-soldering of bad joints. My two misbehaving fullnuts were both fixed by this service.

-- KS



yes, it's a fullnut, so not all hope is lost :-)
Examining the PCB closely, I found a few tiny metal chips
stuck to some of the contacts. A good cleaning is obviously necessary.
I'll try to get hold of an ultrasonic cleaner, then.
Are there any joints which I should have a closer look at (i.e. known weaknesses of this machine)?


Edited: 26 Sept 2007, 6:26 a.m.


Martin --

Are there any joints which I should have a closer look at (i.e. known weaknesses of this machine)?

Couldn't tell ya. I had the services performed by www.fixthatcalc.com

In addition to my own two units (also purchased on eBay and mailed to me by commercial air, presumably in the cold, rarefied cargo hold), a collegue's fullnut also exhibited symptoms of malfunctioning. I suspect that the age and circuitry of fullnuts make them susceptible to this.

-- KS

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