Path: utzoo!utgpu!water!watmath!clyde!att!cbnews!feb
From: feb@cbnews.ATT.COM (Franco E. Barber)
Newsgroups: comp.sys.amiga
Subject: Re: Dead A500 shift key
Keywords: keyboard
Message-ID: <809@cbnews.ATT.COM>
Date: 9 Aug 88 17:57:19 GMT
References: <599@super.ORG> <6199@pyr.gatech.EDU>
Reply-To: feb@cbnews.ATT.COM (Franco E. Barber)
Organization: AT&T Bell Laboratories, Columbus
Lines: 52

In article <6199@pyr.gatech.EDU> davidc@pyr.gatech.EDU (David Carter) writes:
>[Probably more than you ever wanted to know about keyboards.  Clip and
> save; you may have this problem someday]
>
>rminnich@metropolis.super.org (Ronald G Minnich) writes:
>>Well my poor A500 finally got sick. The right side shift key does not work.
>
>I have a similar problem; my keypad 0 stopped working.
>

...

>The key "switches" are more like what is in calculators:  Each keycap
>pushes down a plastic plunger.  At the bottom of the plunger is a rubber,
>conductive contact.  This contact is mashed against two pads on a membrane
>style pc board, completing the circuit.  The membrane lies beneath the
>entire keyboard, and is connected to the 1x6 pc board.  There are no
>"solder" joints at all on the membrane.
>
>In the bad key on my keyboard (and probably yours) the rubber part has
>stopped being conductive enough.  I measured mine with an ohm meter
>and the value is about 10 times higher than the other keys.  Scraping
>off the top layer of the rubber part made no difference.  Incidentally,
>the rubber piece easily detaches from the plastic shaft (kind of a
>"insert tab A into slot B" arrangement).  Also, the shaft+rubber parts
>are completely interchangeable.  So if you'd rather have your HELP key
>be the one that doesn't work, you can swap them.
>

...

>David Carter		davidc@pyr.gatech.edu


Well, this idea might help somebody with a bad keyboard.
I have several remote controls for TV, stereo, VCR, etc.
The volume-down button on one of them stopeed working one day.
I took the remote apart and found the same rubber plunger pushing against
membranes on a pc board construction that is described above.
The rubber plunger had too high a resistance.

I was able to revitalize the contact by covering the face of the rubber
contact with some conductive paint I bought at a local electronics parts
store. The name of the product I found is "Nickel Print". It is distributed
by GC Electronics, Rockford Illinois, 61101. Catalog No. 22-207.

This products seems to be designed for making repairs to PC boards.
I had a little trouble making the paint stick to the slippery rubber
plunger. I had to scratch the face of the rubber plunger to give the
paint a good surface to grip onto.

Franco