10 Jul
2014
10 Jul
'14
4:11 p.m.
On 2014-07-10 6:05 PM, Tony Duell wrote:
The schematic in the AT tech ref would support this as well, it
shows
the "sense" lines from the keyboard matrix being pulled up which would
suggest switches instead of capacitive keys.
Yes that is what I found there is only a schematic for the 101 (102) key
keyboard.
The original
PC was definitely capacitive, I have taken them apart to
clean them and I believe the 84 key AT keyboard was capacitive too, but
Agreed.
I've had them totally aparttoo (well, I _would_). I've also had
a tyype M totally apart (to the point of cutting off the heat stakes
(they were replaed with small nuts and bolts) and taking the flaps and
membrane layers out. The one I worked on was certainyl a membran contact,
not capacitive. I am not positive and the AT tech ref does not
say. The keyboard
I was going to suggest looking at the schematics in the AT
TechRef, and
then I rmmembered that for oome odd reason the only scheamtic fro the 84
key keyobaard is the one for the little LED PCB. The keybaord itself is
not there.
I have the 84 key keybaord somewhere, bot not to hand, or I'd open it up.
The sens amplifier chip i nthe capcitive units is one of those square IBM
metal cans, it's very distinctive.
Yeah IBM used that packaging for a long
time, I don't ever recall seeing
an IBM manufactured part in a epoxy encapsulated dip package, there
where lots that where manufactured for them and stamped with house
numbers. It seems that IBM used their chip manufacturing to produce
components that they could not buy anywhere.
-tony
Paul.