Hi Guys,
I'm trying to revive a keyboard (integrated into a vintage computer so
it's kinda important) - this is the kind where there's a PCB with lots of
"pads" in the scanning matrix, and the keys push a little pad of "conductive
rubber" down onto the PCB pads to make the connection.
Several of the keys on this keyboard require excessive pressure to make
contact - I've tried cleaning the pads, and (gently) the surface of the
rubber, however it appears that the rubber has increased in resistance.
The good keys measure 200-300 ohms from one end of the conductive rubber
pad to the other with only mild pressure - the bad keys measure 5k-10k
unless you really squeeze them - under pressure they drop to 1k - 2k,
which appears to be barely enough to trigger a detection.
Anyone know what the failure mode is? I though perhaps the rubber bits
had cracked, however this does not appear to be the case.
Anyone have any tips/tricks to fix this problem?
Regards,
Dave
--
dave04a (at) Dave Dunfield
dunfield (dot) Firmware development services & tools: www.dunfield.com
com Vintage computing equipment collector.
http://www.parse.com/~ddunfield/museum/index.html
Received on Mon Sep 06 2004 - 22:10:30 BST