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