19 Aug
2013
19 Aug
'13
1:03 p.m.
The
'compact' keyboard is stuffed with 4000-series CMOS ICs. Whether HP
did the sensible thing (for them, and a pain for us now) and used a
microcontroller in the later keybaord I do not know. What does your
keybaord contain in ternms of ICs?
There's a small PCB labeled 98203-66501 mounted to the bottom of the chassis; the keyboard PCB is plugged into it via a
ribbon cable. It's
full of ICs, though they appear to be labeled with HP's custom numbering.
The compact keyboard is a lot of 4000 series CMOS. Mostly 4051
multiplexers. Oddly, the key swithces i nthsi keybaord are not wired as a
matrix. One side of each swithc is grounded, the other side goes to an
input on a 4051. Hence there are a lot of them.
As I am sure you know HP published equivalents lists from time to time in
'Bench Briefs'. I think those are on the web somewhere. One thign to be
aware of is that HP removed ICs from the list if there was no supported
device usign them any more. So you may need to check all the lists you
can find. In any cae, if you post the numebrs here (most likely they will
start 1820-) I, or somebody else, can look them up.
Incidentally, HP did use COP400 seires microcotnrollers at that time.
These came in small0ish pacakages, so the fact that there are no 0.6"
wide ICs o nthe board doesn't mean there are no microcontrollers,
unfortunataly.
[Encoder]
Without knowing the pinouts I was hesitant to start
prodding at things.
Besides, the rear cover just snaps off, it's easy to look at :).
I think you need to identify at least some of the ICs, THen you can find
power and ground quite easily. The encoders normally have 4 wires as I
mentioned.
As you have discovered these enocders do come apart. The light source is
an IR LED (so if you've put 5V striaght acorss it it's probably dead by
now!).
I did not -- I measured 5V across it when the keyboard was plugged in,
that's all.