HP-41 keyboard issue - help from the hardware gurus here

My HP-41CV (fullnut) turned into an HP-41CL has an issue with the minus (-) key: I need to press it rather hard for it to register.

Now before I open it up and start some kind of a hit & miss adventure, I thought I'd ask the gurus of this board for a virtual hand. How exactly do I go about fixing/cleaning out this issue (baby steps please, I'm a software guy).


Hello Geir,

Take apart the calc with the usual anti static precautions.

Obtain a small tube of DeOxit gold. Find the pinhole on the circuit side of the keyboard centered on the offending key. This is the centre of of the dome. Introduce a tiny amount of the deoxit into the pore on the circuit side of the dome.

Exercise the key and clean up any fluid forced back out the pore during your key press exercise.

Assemble and test. DeOxit works wonders. Still having a problem? Combine the DeOxit exercise with the following. Secure a stiff fine wire and introduce it through the pore. Swizzle it around and remove it. Introduce the DeOxit.

Reassemble and test.

Typically the key responds perfectly after the DeOxit procedure.

Hope this helps.

I would post a picture but I am not at home at the moment.


Go to this link:


and scroll down the page until you see the tube. If you do not have or cannot get DeOxit try the pin and some denatured alcohol.

Edited: 15 Apr 2012, 10:09 p.m.



On that page, there is a range of small tubes of that stuff. Which one should I use (what percentage of the solution)?

Or, even better; Which one of these should I buy:


Edited: 16 Apr 2012, 4:12 a.m.



For some reason my iPad will not function the Link format.



Thanks a whole bunch. I ordered it and will commence the surgery upon its receipt.


A picture would also be very welcome :)


The red arrows indicate the pores, the yellow arrows the circumference (edge) of the snap domes.


Close up of the FULLNUT

Close up of the HALFNUT

cheers, Geoff

Edited: 16 Apr 2012, 2:33 p.m.


You're Da Man.

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