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HP Forum Archive 14

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HP-25 dots and dots...
Message #1 Posted by Cedric F on 24 Dec 2003, 3:03 p.m.

My HP-25 begun to act strangely : all the dots on every digit ar lit. I know that's the signal of low battery but my battery are brand new.

All calculation seems to works ok but it's hard to know where is the real decimal dot...

Program is also working good

I opened the calculator and every contacts seems to be ok. Under the display, there is a kind of potentiometer, what is the use of this adjustment (no i don't totch it yet...)

thanks you for all your answers.

Ced

      
Re: HP-25 dots and dots...
Message #2 Posted by Michael F. Coyle on 27 Dec 2003, 11:17 p.m.,
in response to message #1 by Cedric F

Hi Cedric,

The potentiometer is used to adjust the threshold for the Low Battery warning. I don't know how it should be adjusted though, so best to leave it alone for the time being.

I did measure all the voltages in an HP-21, including this circuit. I could dig up this info if you feel like trying the adjustment.

- Michael

            
Re: HP-25 dots and dots...
Message #3 Posted by David Smith on 29 Dec 2003, 1:25 p.m.,
in response to message #2 by Michael F. Coyle

Mark the current setting of the pot with a fine pointed marker (use the screw slot as the arrow) and twiddle away. You can then return it to its original setting.


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