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HP11C permanently ON - Printable Version

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HP11C permanently ON - Walter B - 01-19-2007

Hi all,

yesterday, my HP11C (made in USA 1985) surprised me with a feature not seen so far: it didn't shut down! The day before it was working like always, but now it didn't accept any input from the keyboard anymore, displaying 1.7E-3 all the time. Removed and replaced batteries after some minutes: 1.7E-3 returned. Removed batteries again, shorted the terminals for some time, reinstalled batteries: all elements of the LCD show up, except the holy star! Stays this way for 12 hours now.

Any ideas??

Re: HP11C permanently ON - Vieira, Luiz C. (Brazil) - 01-19-2007


I'd suggest briefly shorting the batteries' terminals with the batteries installed, as stated in all Voyagers manuals. The brief short circuit must be fast enough to ensure the voltage in their terminals briefly drops to zero AND THAT the batteries' energy is not drain too much. Of course, even the briefest short will be equivalent to some hours of calculator activity.

The reason to keep the batteries in place has already been discussed in this forum some time ago, and I still believe that the batteries make sure the voltage in their terminals never goes higher than 4.5Vcc, so there is no way to dammage the calculator with an ESD if they are in place. If you remove the bateries and short the calculator terminals without them, chances are that residiual static electricity is trasnfered to the calculator circuitry and it may hang. It may happen.

I prefer loosing a few hours of calculator activity...

My 2ยข.

Luiz (Brazil)

Edited: 19 Jan 2007, 6:53 a.m.

Re: HP11C permanently ON - Walter B - 01-21-2007

Bom dia Luiz,

muito obrigado! It worked like a charm. Thanks for bringing my HP11C back to life!

Cumprimentos de Alemanha d:-)

Re: HP11C permanently ON - Vieira, Luiz C. (Brazil) - 01-22-2007

O prazer foi meu. (My pleasure)

Hope it keeps working fine.

Luiz (Brasil)