The Museum of HP Calculators

HP Forum Archive 14

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HP 25 faulty
Message #1 Posted by sylvain on 13 Feb 2004, 12:20 p.m.

Hi list, My HP 25 has a display problem which arrived sudenly, yesterday no problem today it displays only the last zero on the right side of the screen, and that zero is much more brighter than usual. When i key any of the keys no response at all. Is that serious and is there any way to fix it?

      
Re: HP 25 faulty
Message #2 Posted by David Smith on 13 Feb 2004, 12:25 p.m.,
in response to message #1 by sylvain

The most likely problem is a bad ACT chip. The only source for a replacement chip is another machine. You can use the chip from a HP21/25/25C/29C/67/97. It is the big 22 pin chip with the rows spaced 0.4 inches.

            
Re: HP 25 faulty
Message #3 Posted by Victor Koechli on 13 Feb 2004, 7:46 p.m.,
in response to message #2 by David Smith

I might add that in some cases the problem could go away if the machine is left turned on for some time. Some of them have to get warm in order to work properly. Could take anywhere from several minutes to an hour.

Cheers, Victor

                  
Re: HP 25 faulty
Message #4 Posted by David Smith on 14 Feb 2004, 12:46 p.m.,
in response to message #3 by Victor Koechli

But with loss of display scan, you can easily fry the LED digit that is lit.


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