HP-25: battery problems


It seems I've another problem with one of my Woodstocks: I've got 2 HP-25s but just one battery pack. One of the machines works without problem with the battery, the other though sometimes shows an "unstable display", i.e. the display goes off and on or shows the low bat indicator (decimal points) even if the pack is fully loaded. However, the machine works perfectly well with the battery when connected to AC power. Does anyone have an idea what's
wrong with the machine? Thanks for helping!


Well, first of all, clean you battery contacts... before having a look at the electronics...


It sounds like the battery contacts in the calculator are slightly corroded. Try cleaning them with some very fine sandpaper (but be careful to not wear them away). Also an HP service person recommended placing a small wad of aluminum foil between each battery contact and the battery because the battery conatacts may not be even and the two cells in the battery pack (depending on how it was built) may not move independently.


Thibaut, David, you both were right! Thanks a lot for the good hint! I cleaned the contacts using a ballpoint-pen eraser (one of those that are available in form of a pencil) and afterwards the calc passed a 1h+ test without any failure :-) Thanks again!

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