Posts: 1,089
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Joined: Dec 2005
I'm sure others will know better and I don't own one of these fine cals but here is a reasonable guess: After so many (many;) years capacitors tend to go bad. In my experience, this can cause a lot of nasty failures. If no one else will come up with a better idea, replacing all capacitors is worth trying.
Thomas
Posts: 883
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Joined: Feb 2006
Most caps in HP handhelds are tantalums... it's rare for them to fail.
The problem is bad ACT chip, it was damaged by the charger being plugged in with a bad battery or no battery in place. The battery is the load for the charging circuit, if the battery is open and presents no load, the voltage inside the calculator rises to 10 volts and damages the integrated circuits.
The only source for the chip is from another 21,22,25,25C,29C or 67. The 27 is not compatible. The ACT is the 22 pin DIP at the bottom of the processor board.
Edited: 19 Feb 2006, 9:53 a.m.