Message #9 Posted by Randy Sloyer on 7 Dec 2003, 3:49 p.m.,
in response to message #1 by Marc
Without question: NO BATTERIES. Keep it dry and clean. That's it.
IMO, the two most popular ways to kill a 48:
1) Leave batteries in it and have them leak. If it is in the normal operating position, its cosmetic damage only that can be cleaned up as it just leaks on to the battery clips and cover. If it is keyboard down, the electrolyte gets into the keyboard - end of calculator.
2) Heavy use in dirty environments. Survey use without a cover claims most of the 48's. Fine dirt works it way into the keyboard and compromises individual key switches. You end up with intermittent keys. Concrete plants are particularly nasty. Again, no solution.
The whole electrolytic capacitor debate does not apply to HP calculators. A lot of this is technical urban legend stuff - comes from old time tube equipment that runs at 150 volts and above for the plate supplies. The filter caps dry out with time (we're talking 30 years and older here) and when hit with these high voltage levels, they tend to arc internally and short. Best to replace them, period. The variac method does help for really old equipment that you would want to keep working with 100% original parts. Otherwise, it's always best to replace them.
There is only one electrolytic cap in a 48 - a 1000uf 6 volt memory backup/battery bypass cap. Everything else is a sealed tantalum. Good for just about forever. Modern 6 volt electrolytics with pure DC applied from batteries will last just about as long if not overheated.
Edited: 7 Dec 2003, 7:41 p.m. after one or more responses were posted