|Re: A pair of 21S with sticky keys|
Message #2 Posted by Philippe Lasnier on 31 Mar 2009, 8:42 a.m.,
in response to message #1 by Peter Klein
I guess that if you don't really want to open up the Pioneers, then the only thing remaining is trying to clean them "from the outside".
My somewhat narrow experience in the matter dates from a few months ago. I had read that besides the usual boil-in-this boil-in-that directions, you could also clean up using an ultrasonic cleaner. One guy in particular was reporting that he always cleaned mobile phones (as a business reselling them) that way.
Having acquired an HP-48SX whose keyboard was constantly playing up, I thought I had nothing to lose; I bought an ultrasonic cleaner with a large enough tank to fully immerse the calculator, and put it through a few cycles with warm water and the built-in heater full on.
I actually overdid it a bit, because the paintwork on the bezel became dull, and flaked off where it had been impacted (the impacts sites were not visible beforehand) - BUT the keyboard worked again! :-)
Later on I tried the same on an HP-28S which was unbelievably dirty, grimmy, and seemingly melted in places, but working. I was less successful: I managed to clean it in a major way, but I've lost 6 pixel columns on the display.
So, a 50% success rate. If you've got nothing to lose, then I would suggest that you clean up the calculators as much as you can first by hand, and then cycle it a few times in an ultrasonic cleaner (assuming you can get access to one).
Take the batteries off first, obviously, and short the battery contacts briefly (or leave the calculator untouched for a while) to discharge any residual energy (the one used for preserving the memory while the batteries are off). After cleaning, leave somewhere warm for a while (like an airing cupboard, e.g. 50C/125F), a day or two, so that all moisture will evaporate.
The problem with sugary stickyness is that an ultrasonic cleaner (which dislodges dirt particles by cavitation) may not be able to shift it right away. The sticky stuff would need to disolve in the water first, so you may need to "soak".
This posting is longer than I thought - sorry. I hope it helps, or gives you ideas.