Cleaning older models


Sort of connected to my other message about my flakey 34C, I figured that when I had it apart, I would clean it up as well. I was a little surprised at Les's post about taking the numbers off his HP-80 with some alcohol. I used to clean my HP-41C this way, just to get oil off the keyboard. Maybe they fixed this problem in later models, but I'm nervous taking any cleaner to the 34C. Is this okay to do? Any idea why it happened to Les's? I also see a 65 on Ebay with no letters on the faceplate. Scary.


I suspect that skin oils and prior cleaning may contribute to the breakdown of labels. When I have cleaned my 45, 65, and 67 with dilute isopropyl, I think I got lucky, but the HP80 spooked me.

Randy of has recommended light soap and water at most. Others here have said don't even attempt to clean unless the unit is irretrievably dirty.

The Classics and Woodstocks seem especially vulnerable to this--silk-screening on plastic doesn't say "durable" to me, at least not in the sense of surviving decades of heavy use in the hands of previous owners who don't cherish these things like we do. The lettering on the metal keypads of the Spice, Pioneer, Voyageur, and 48G/GX/S/SX looks a little more avid to me, but after the HP80 horror show any future cleanings for me boil down to the classic Clint Eastwood question "do ya feel lucky?"

At least I know that if lettering fades on any of my calcs I can make perfectly serviceable overlays so I can see at least what the lettering is supposed to say! That HP-80 has been cosmetically flawed, but with help from here and a little ingenuity I have been able to restore it to full legibility and usability. I was playing with it just tonight. Didn't have the heart to until I got that overlay on.

I have a 34C that is a 1980 model but feels light in the hand, certainly lighter than the 1980 33C. I hope to heavens I got an early version of one of the "good" 34C's. I know the 15C eclipsed the 34C entirely, but I really love the twinkly LED as it labouriously Romberg's its way thru an integral :)


Edited: 15 Feb 2007, 5:55 p.m.



Some mild detergent in an ultrasonic cleaner for a few minutes did a good job. After that I use some spraycan I bought at a carshop used for maintaining the plastic parts inside a car. Please do not use the ones with teflon in it for that will make the calculator shine which is not original.




It might have been courageously to try, but I cleaned a pair of old calculators and an Newton using Waschbenzin (benzine?!). It easily removes greasy dirt and seems not to corrode plastics.

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