hp 42s


Could anyone tell me if water is necessarily fatal to a hp42s? my trusty hp42 was left overnight in the rain. Can it be dried out, or are there internal parts that just wont come back to life? What can i do? I feel like I've lost my best freind!


Well... I guess it's bad news for you...

Try to remove the batteries and dry it up with an hair dryer. Insist on the battery compartment and pray for the internals to dry up without too much oxydation.

It is somehow possible to open the calculator but this is not a damageless solution...

I guess you want to browse ebay for a replacement unit...


If you did not power it up when it was wet you have a chance. Just remove batteries and let it dry out for two 24 hours. Put in new batteries, it should power up. If not contact Randy and www.fixthatcalc.com he would advise you.



the rain water has chemicals taken in the atmosphere that may be harmfull to the metal surfaces (maybe some decades ago it would be harmless...). I'd suggest washing the HP42S with destiled water (after removing the batteries) to remove the residual chemicals that might react with the metal surfaces after drying the rain water. After that, drying out the calculator might be done without much worries.

Hope you succeed!

Luiz (Brazil)


I removed batteries and battery cover and dried it (without actually opening the case) using a hair drier, then a blow heater for several hours at about 30degC but can't really tell if the insides are completely dry.

re-installed batteries several times but no luck. dried for a bit longer, inserted batteries and it came back to life and seemed to work , however the on/off/exit button does not function.
if i remove the batteries and then replace them, there is no response. if i then leave it for an hour without batteries and replace them again, it starts up again but no on/of/exit key

any suggestions?


You really should wash it out with DI water. Water itself does not pose much of a threat to electronics until other subtances are dissolved in it, giving it conductive and corrosive properties. Take out the batteries and place it in a container filled just enough to cover it. Move it around a bit, perhaps flip it over, drain it out and repeat with fresh distilled water two more times. Place it in an oven or toaster oven at its' lowest setting for a few hours and remove it to cool down.

Good Luck,


Standard procedure for reviving electronics gear which has
fallen in sea water: 1) shake out the sea water 2) immediately put in fresh water (prolonged storage possible) 3) shake out fresh water 4) put in distilled / demineralized water - stir well / shake / press buttons 5) shake out distilled water 6) put in 100% alcohol (ethanol) - stir well / shake / press buttons 7) let it dry in sunlight (oven not recommended - may melt the plastic). 8) if alcohol smell is gone, try it with fresh batteries and cross your fingers.


I would suggest that you follow Luiz et al's instructions. Alcohol can and will leave the screen of some old calcs such as the 41 milky and ruined. You can use alcohol, just use destilled water afterward. I have read here that someone got good results by drying his calcs in a gas oven with only the pilot light on, the oven was something like 120 degrees and safe for the unit. A 100% solution of Sauza Hornitos tequila, applied internally to the calculator cleaner has worked well for me. PRN.


I've seen a nice experiment lately concerning a TV set and distilled water. You won't try this at home. The usual dust inside devices dissolves apparently quite well in ADest, making is conductive enough to have a fancy lightning show. Your post implied that but I wanted to point it out explicitly. Too bad that CFC is out of discussion (for a good reason)...



Obviously the TV was powered up when the destilled water was spilled into it. Known to TV repairmen as the flower pot syndrome (light) or aquarium syndrome (severe). As for the soaked calculator (or any other such equipment) any person able to THINK would immediately remove the batteries before applying cleaning procedures, so it was implied. The ethanol indeed may be dangerous to some displays but does a very good job to dry the equipment. Finally, don't forget all this is a final rescue attempt to revive equipment that otherwise will be dead.
Some make it, some don't. So it is worth a try.

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