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Changing Batteries on HP-42S - Printable Version

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Changing Batteries on HP-42S - Thomas Cox - 11-19-2008

I have a HP-42S that has been upgraded to 32k ram, so losing the contents of memory when changing the battery can be bad news. Yesterday I tried to turn the unit on after not having used it for several weeks and found that it would not turn on.

Following the instructions from Randy Sloyer of Fix That Calc, I removed the batteries by tapping on the calculator with the battery cover removed to prevent any possibility of shorting across the terminals. I then held the calculator sideways so I could stack the batteries one on top of the other without shorting the terminals.

Turning the calculator on showed the message, "Machine Reset." The programs were all there (about 15k) and workable.

If you get the low battery annunciator, turn the calculator off before replacing the batteries using the method described above.