Re: Display on HP-25C shows 000000´s Message #2 Posted by Victor Koechli on 13 Oct 2003, 5:22 a.m., in response to message #1 by Matti Övermark
I'd suggest taking the calculator apart and carefully cleaning the interior contacts that connect the keyboard and the display to the main PCB. While doing so, you can also check for broken traces or loose solderings on the main PCB.
Another oddity of these calcs is that some of them only work after a warm-up period of up to an hour, so if cleaning does not help, try leaving it turned on for some time. I have a HP-25 with that behaviour. It's supposed to be a problem of the ACT chip, and there are a number of fixes you can try (search this forum's archives for more information).
One thing, though: Never, under any circumstance, connect your HP-25C to the AC adaptor when you have no battery installed or if there is even the slightest chance that the battery contacts could be bad! You could kill the calculator's RAM chip just by plugging in the adaptor! In the C-version, the RAM is connected to the power supply even with the calculator off.
Cheers, Victor
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