3 Feb
2014
3 Feb
'14
1:20 p.m.
Hi,
I've just got (another!) AT&T UNIX PC keyboard to replace the one with
missing keycaps and -- woe and behold -- this one has a few dead keys!
For bonus points, it doesn't use the same switches as the other
keyboards: it uses ITW "Magnetic Valve" keyswitches instead --
Are those the ones with a core that's sturated by a permanent magnet, and
which is desaturated when the key is pressed so that there is increased
coupling between 2 'widnigns' on said core?
HP used thsoe in the HP9845 (at least). Really odd to test, you had 2
pairs of pins that were dead short irrespective of the state of the key.
I had to take one apart to figure out what was going on. Acutally HP also
had some 3-state ones (up, pressed, pressed hard) with 2 cores, and 6
connections (there was one pair of pins that went to a winding on both
cores, then separate windings, one on each core, to the other 2 pairs of
pins).
-tony