The Museum of HP Calculators

HP Forum Archive 13

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Message #1 Posted by Hans on 23 Aug 2003, 9:34 a.m.

I changed the batteries on my HP15 calculator. Now I have only illegible characters on the display. Is my calculator defect or what's the problem? Is there anyone who knows abaout this problem? Thanks: Hans

Re: HP15C
Message #2 Posted by Vieira, Luiz C. (Brazil) on 23 Aug 2003, 9:59 a.m.,
in response to message #1 by Hans

Hi, Hans;

sometimes it happens that old batteries have a voltage difference to the new ones that's enough to "hang" the calculator. You may start with the [ON]&[yx] pressed together: this is the first attempt to get the calculator back to normal operation after a [ON]&[-] memory clear.

If you get your Owner's Handbook and search for the Battery replacement text (appendixes) you'll also find some information about resetting calcualtor's memory. One of the most simple procedure is the hardware reset: a single, brief shorten in batterie's terminals. Yes, you get a piece of wire or any conductive material (a paper clip, as mentioned in the manual, may give you some trouble if bending it to fit in) and briefly, very briefly, connect both (+) and (-) poles of the batteries. As for safety precaution, do not remove the batteries: they will ensure no more than 4.5V will be present in their terminals, even if you have electrostatic charges in yor body, what could dammage your calculator. To be even safer, touch some GROUNDED metal parts before doing this.

Hope this helps.

Luiz (Brazil)

Re: HP15C
Message #3 Posted by bill platt on 23 Aug 2003, 12:22 p.m.,
in response to message #2 by Vieira, Luiz C. (Brazil)

Hello Luiz,

About this short the terminals thing: If you leave the batteries in the compartment and then short the terminals, you will send a large current through the shorting wire, and trash the batteries. Or am I missing something?



Re: HP15C
Message #4 Posted by David Smith on 23 Aug 2003, 12:54 p.m.,
in response to message #3 by bill platt

Those tiny batteries can't supply enough juice to heat anything up with just a one second short. It is HP's recommended proceedure.

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