14 Jan
2008
14 Jan
'08
11:58 p.m.
-------------- Original message from ard at p850ug1.demon.co.uk (Tony Duell):
--------------
Yes that is what I'm finding . The donors have more value than the
pieces I'm working on.
Tony, Do you have one of these tools ??? and/or what it looks like
- Jerry
Jerry wright
g-wright at att.net
I know the
design well. The contacts spring togethe, and are kept apart
by a plastic pin in
the plunger when the key is not pressed.
The keycap is a press-fit into the plunger, which means it slightly
stretches the latter. In time the plunger cracks anyway, even if you
don'y drop anything on it.
The other prolem is fitting new contacts. At one time you could buy
individual contacts and more importantly a tool to hold them and press
them in place without damaging them. Said tool was (at least) sold by
Radio Shack Nationl Parts Centre and HP (I have part numbers for both),
but AFAIK it's now unavailale, It's possilble to use long-nose pliers
carefully, but it's very easy to mangle the contacts.
What I would like to find is a doner type of system that does not have
any value so I can rob the middle piece.. (typewiter) ???
I've seen this type of keyswitch on (at least) the following :
DEC VT50 series
DEC VT100 series
TRS-80 Model 1 (early version only)
TI 99/4a
HP80 series (HP85, etc)
HP9915 keyboard (very rare!)
HP98203 (small keyboard for the HP9816)
HP2623 (IIRC) graphics terminal
Unfortunatley none of those are exactly common. When I repaired my 9816,
I was lucky enough to find a 'spare' VT52 keyboard PCB i nthe junk box,
given to me with a load of other DEC spares, which provided contacts,
plungers, even keycaps.
-tony
15 Jan
15 Jan
4:33 p.m.
Yes that is what I'm finding . The donors have
more value than the
pieces I'm working on.
I suspect the most common machine to have that keyboard is either the
TI99/4a or the HP85. I wouldn't suggest raiding either one for keyboard
parts, but if you could find an HP85 where several of the custom chips
have failed, it could be a sourve (mind you if you know of such a
machine, I'd want the entire keyboard to make a keyboard for my 9915.
It's electrically rhe same matric, just in a keyboard-only box, if you
see what I mean, so an HP85 keybaord could be wired up).
Tony, Do you have one of these tools ??? and/or what
it looks like
I wish. I have the HP part number for it somewhere, but the Agilent
partsfinder had never heard of it.
I asusme it's a rod with a couple of carefully-designed slots in the end.
You put the contacts into the slots and ues the tool to push them ionto
the keyboard frame and PCB. Then solder them.
If you don't have the tool, it's possible to grip the contacts carefully
in long-nose pliers and wrok them, a bit at a time, into place. You then
have to re-form th top edge of the contat.
-tony
5:22 p.m.
New subject: Keybard repair help. Older terminals
Tony Duell writes:
Is the TI-99/4A so uncommon? At least here in the states, you can't hardly
throw a rock without hitting one. Ok, maybe not that common... but my
understanding is that TI basically flooded the market with these things in
an attempt to win out against Commodore and Atari in the home computer
market in the 80s...
(Not that I love the idea of destroying any working "classic" computer for
parts, it's just that if you're going to, you might as well make sure it's
nothing anyone's going to miss...)
- Josh
Yes that is
what I'm finding . The donors have more value than the
pieces I'm working on.
I suspect the most common machine to have that keyboard is either the
TI99/4a or the HP85. I wouldn't suggest raiding either one for keyboard
parts...
16 Jan
16 Jan
5:56 p.m.
New subject: Keybard repair help. Older terminals
Is the TI-99/4A so uncommon? At least here in the
states, you can't hardly
THey're not that common across the Pond. But certainly not the rarest
machine around either.
throw a rock without hitting one. Ok, maybe not that
common... but my
understanding is that TI basically flooded the market with these things in
an attempt to win out against Commodore and Atari in the home computer
market in the 80s...
(Not that I love the idea of destroying any working "classic" computer for
parts, it's just that if you're going to, you might as well make sure it's
nothing anyone's going to miss...)
Agreed. I don't like raiding any classic computer hardware for parts, but
then again, Id be prepared to raid a common home computer in order to
restore some rare machine or peripheral. Hence my list of machines that
I've come across using this keyoard mechanism, there might be something
on there that you have anexcessive number of and would be prepared to
sacrifice.
-tony
15 Jan
15 Jan
6 p.m.
machine, I'd want the entire keyboard to make a
keyboard for my 9915.
It's electrically rhe same matric, just in a keyboard-only box, if you
see what I mean, so an HP85 keybaord could be wired up).
I'd use a common PC keyboard and a small microcontroller :o)
I wish. I have the HP part number for it somewhere,
but the Agilent
partsfinder had never heard of it.
Is it on old hp catalogs? I have some :o)
7:30 p.m.
People:
I have some code (in basic for bascom) to make a PS2 keyboard spit ASCII
data. If I publish the circuit (a microcontroller and 2 or 3 resistors) and
the code, with the compiler, will it help you, keyboardless people, to fix
your systems?
I'm sorry I cannot give much more help, I have none of your classic
systems :o)
Greetz
Alexandre
16 Jan
16 Jan
6 p.m.
machine, I'd want the entire keyboard to make
a keyboard for my 9915.
It's electrically rhe same matric, just in a keyboard-only box, if you
see what I mean, so an HP85 keybaord could be wired up).
I'd use a common PC keyboard and a small microcontroller :o) I wish. I have the HP part number for it
somewhere, but the Agilent
partsfinder had never heard of it.
Is it on old hp catalogs? I have some :o)
7:33 p.m.
Good luck.. The 9915 keyboard interface is for a
matrix-of-switches dumb
keyboard. I don't know how fast it scans, a microcontorller might be able
to keep up. The main prolem is that it's not at TTL levels (I think it's
at 6V CMOS levels).
Tony, as fast as it could be, just an interrupt onto the first (or in
all) of the columns/lines and you can scan the entire matrix in sync with a
microcontroller. Thats what I did in a MSX keyboard converter. And it can be
done - as far as I know - to any old microcomputer avaiable
It isn't just a matter of rewiring switches - but the praticity of using
any PS2 keyboard - and better - the best keyboards you can find. I hear
someone shouting "IBM MODEL M" from way behind :o)
Greetings from Brazil
Alexandre
In a "hardware hacker" day :oD
6026
days inactive
6028
days old
7 comments
4 participants
participants (4)
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alexandre-listas＠e-secure.com.br -
ard＠p850ug1.demon.co.uk -
derschjo＠msu.edu -
g-wright＠att.net