Keybard repair help. Older terminals

[Tony Duell]

> 
> I seem to have my share of  Terminals that have bad  keyboard parts. 
> 3 that I'm working  now have the same type of Keyboard.  These 
> are Hazeltine 1500 and ADM 3As.   These have an molded base
> with fingers that stick up and a second square piece that slide into the base
> and makes and breaks the finger contact. It also has a square opening in the
> top for the key cap.  So when someone  drops a heavy object on the the key board
> this intermediate    piece cracks in the corners and binds in the base.

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