41cv freeze in user mode


Hi all,

I know this is my seconde post about this subject, but I can't resolve it!! (see "Is my 41 sick ?" on 05/14 )

I explain my problem: When I switch in user mode and type any of the key of the first two rows the calc freeze!! Only backspace+on can stop the calc.

I precise that the problem occur only when there is nothing assigned on the key. If I assign something to a key and then press it in user mode, that works.

But after that if I remove assignement on the key, the problem re-appear!!

I do not have any module extension, and try many times a memory clear, but the problem is still here...

Is there a better way (other then doing a backspace+on) to be sure that the memory is really cleared ?

I love my 41, so please help me....




According to your 41 symptoms, it looks like a faulty ROM chip is the one to blame.

A service ROM will positively detect the offending one.

So far I've only found two such ROM failures, this is not usual, but seems your 41 has been hit by that illness.

Sorry for the bad news (Wish I was wrong)



Hi Diego,

if it's a malfunctioning ROM,

then I suspect it to be ROM 1.

I have several HP-41 pcb's,

some of them have faulty RAM chips,

two or three have a faulty ROM,

and it's always ROM 1 so far,

according to the Service ROM;-)

Best Regards



Hi all,

Thanks for responses.
Huumm, it's very strange that suddenly this kind of fealure can occur... I have not opened the calc and not put my electro-static fingers inside :)

In this time I try the only manip I'v not done. Removing the battery for a long time and see....

I have try this last week but not enought time, only five/six days. But when I turned the calc "on" the display remain with the last "12345" I have typed before removing the battery...

All the others functions seems to work well, so now "Wait and see..."

I give you news if any.



Bonsoir Denis,

Afin d'être certain de réinitialiser complètement la Hp, il ne suffit pas d'attendre après avoir enlevé les batteries. Les condensateurs internes maintiennent une charge importante.

Après avoir enlevé les batteries : courcircuitez les deux contacts cuivrés les plus extrêmes avec un conducteur de votre choix.

Si le problème subsiste, alors vous pouvez être certain que c'est un problème de ROM tel que décrit par Raymond et Diego.

Translation :

Good evening Denis,

To ensure full reinitialization of your HP, it is not enough to wait after having removed the batteries. The internal capacitors can maintain quite an important load.

After removing the batteries: short the leftmost & rightmost coppered contacts with a conductor of your choice.

If the issue remains, then you can assume that it is a ROM problem as described by Raymond and Diego.



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