slick bits in computers (WAS: VAXen Rule!)
ard at p850ug1.demon.co.uk
Fri Aug 11 16:37:15 CDT 2006
> > Not sure I'd agree on the reliability...I've spilled my fair share of
> > coke into keyboards, and contact-closure keyswitches just don't cut it
> > for me unless they're sealed.
> You can make switches that are cheap and nasty, and you can make
> switches that will last 100 years - and everything in between. If you
> want a fair comparison, match the HP keyboard against a quality
> "mechanical switch" keyboard, not a Chinese piece of crap. Lets face
For some reason, the HP9830 did not use this trasnformer keyboard, it
used a matrix of (IIRC Cheey brand) keyswitches. And yes, I have had to
replace _one_ of those on my HP9830 (which is 33 years old, so I am not
I do wonder, though, if the transformer keyboard would be that much more
expensive to produce. The encoder/controller board was about 20 TTL chips
then, now it could be triviailly fitted into a PLD or ASIC (if you did
the latter, you could fit the comparator in as well). The keyboard
'transformer' PCB is just a double-sided PCB, easy to make now, and the
only components on that are a diode for each pair of keys (compared wit
ha diode per key for a decent mechncial keyboard)
As regards the mechanical bits, there are 4 for each key :
The keycap (same as for a mechancial switch, basically)
A plunger (plastic moulding) with a metal disk heat-staked to the end
A mounlded plastic housing.
No worse than the parts for a mechanical switch, and shouldn't be any
more expensive if produced in quantity.
> it, HP stuff of that era was pretty much the pinnacle of engineering.
One reason why I like their _old_ machines.
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