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HP Forum Archive 09

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HP11C ,not working
Message #1 Posted by Jean Minazio on 30 Aug 2002, 9:25 a.m.

My HP11C is not working when changing batteries. It hangs up with some segment on the display ON. Is there any change of a chip or resonnator failure ? Please advice on how to fix it. Best Regards Jean Baptiste

Re: HP11C ,not working
Message #2 Posted by Ellis Easley on 30 Aug 2002, 9:54 a.m.,
in response to message #1 by Jean Minazio

Do you have the user's guide? There is probably a chapter or appendix about "troubleshooting". There may be some key combinations that can reset the calculator. If the keyboard resets don't work, some of the HP calculator manuals recommend shorting the battery terminals with a metal object in case the calculator won't work after installing fresh batteries. In some cases, the batteries are to be left in place, in other cases the batteries are to be removed. It sounds wrong to short the terminals of the batteries, but some of the HP manuals recommend it for some of the calculators that run on button cells. The reason for shorting the battery terminals is to make sure the calculator chips receive a low enough supply voltage so that the memories will "forget" all the meaningful data in them. Sometimes data remaining in memory, but corrupted, will cause the calculator to think it is in a certain state. When the data in the memory returns to a default "power up" state, the calculator knows to re-initialize everything, then it will give the message "memory lost" or "pr error".

Re: HP11C ,not working
Message #3 Posted by on 30 Aug 2002, 2:20 p.m.,
in response to message #2 by Ellis Easley

try sort circuiting the contacts. Try ON/- (reset sequence). Try inverting polarity for a very short while. And before anything, check the batteries, even if they're new : one bad battery could be the cause of all your problems.

Re: HP11C ,not working
Message #4 Posted by Vieira, Luiz C. (Brazil) on 30 Aug 2002, 3:04 p.m.,
in response to message #3 by


I have one 11C, two (new)12C, one 15C and one 16C. The message Ellis mentions is "Pr Error" (they're all 7-segment display), and it should appear when [ON]/[-] are pressed, as Thibaut mentions. What I strongly recommend is that you shorten (very briefly) the batteries contacts (use a thin wire) WITH THE BATTERIES IN. Depending on the model you have, the batteries will not fit in if placed inverted.

If the calculator does not turn ON, the alternate reset is [ON]/[D], being [D] the key with y raised to x printed in. Press simultaneously (not one after the other, both at the same time) [ON] and [D]. The display changes its contents IF the calculator turns on.

I repaired both HP12C (old-fashion) and another HP11C by simply resoldering all IC's terminals (one IC in the HP12C, two IC's in the 11C).

If you need more info, let us know.


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