Key Sounds in a 42


I'm sorry to annoy, as I have posted this question a while back, but with no responses.

Having searched the archives, I have not been able to find information on the crinkly sound made by the keys of a 42S (I have also heard the sound in a 32S). It sounds a little like cellophane being wrinkled up. Almost all the keys on this particular calc have it. Is the keyboard broken down, has it had pop spilled on it (no other signs of a spill), or something else?

Any opinions?



This sound may appear in any old HP model and is not specific to any particular calculator model.


Some facts about it...

Hope it helps,


Thanks for the link, Massimo. I gained some knowledge of the keyboard construction.

It's not so much a loud click on the return though. This sound occurs as I am pushing the keys down. The idea of cracked domes crossed my mind, as that could make a similar sound. It seems unlikely that all the domes are cracked though, so I'm hopeful that's not the problem.

It almost sounds like a sticky, gooey substance pulling apart, but it doesn't actually feel sticky/gooey. It feels okay, it's just loud and annoying when I'm pushing the keys down. And of course I'm wondering if the keyboard is about gone.


If the serial number starts with ID (made in Indonesia) or it has an M in the fifth position (made in Malaysia), it could well be manufacturing variations in the dome sheet and assembly of the keyboard itself. But... if it was made in the USA or Singapore (A or S in the fifth position of the serial number), chances are very good something was spilled on the keyboard. Pop and coffee with sugar are especially problematic. If you suspect that's the culprit, it's easy to clean.

I'm sure there are some out there who will tell you not to do this but I assure you, it will not harm your 42S. Don't trust me? Then don't do it, it's that simple.

Remove the battery cover and batteries. Now, completely submerge it in a glass baking tray or other very clean container filled with warm (100°F/40°C) distilled water. While it's submerged, press all the keys and swish it around well. Take it out, let it drain, press all the keys and shake it so the water drains out of the case. Dunk it again and repeat. Change the water and repeat the process. Shake it until no water comes out, press all the keys and shake again. Place it somewhere that you can direct an airflow over it. A small fan works quite well, a warm area (~80-100° f) will accelerate the process. Give it at least 24 hours to dry. Do not use hair driers, heat guns or heat lamps. No, don't do that. Time, warmth, air flow and evaporation are your friends. Heat is your enemy.

Put the batteries back in, snap the cover on and see if you've solved your problem.

Under no circumstances should you place batteries back into a unit that may be damp or wet, you'll destroy the keyboard. If after a day, you install the batteries and it acts in any way weird (numbers or functions appear without being pressed, slow to respond, anything out the normal behavior) REMOVE the batteries again and allow to dry for another day. It should be fine after another 24 hours.

Heed the battery warning and the biggest danger in this process is loosing your grip on the unit while shaking the water out.

PS: If the keyboard surround is especially dirty, you can start by taking the batteries out, dust with a light spray of window cleaner and clean gently with a very soft bristle brush. It doesn't take much effort to loosen the crud and you don't want to scrub. Rinse under running water then its right to the distilled water bath. I would not recommend this treatment for units with any blistered finish.

Edited: 2 Jan 2007, 5:22 p.m.


Thanks, Randy. I'll try it.

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