HP9816 keyboard plunger wanted.

Tony Duell ard.p850ug1 at gmail.com
Sun May 28 10:56:31 CDT 2017

On Sun, May 28, 2017 at 4:50 PM, Mattis Lind via cctalk
<cctalk at classiccmp.org> wrote:
> Hello!
> I recently received a HP9816 machine. The previous owner originally got the
> machine without a keyboard but subsequently sourced a keyboard off ebay.
> Unfortunately this keyboard was not in the best shape. One key was stuck
> and when taking it apart it was evident that it has taken a bath for quite
> some time. At least the electronics around the space bar were quite
> affected with corrosion. Luckily this keyboard is quite simple design with
> only CMOS 4XXX IC, and better yet, Tony Duell has already reverse
> engineered it (together with the rest of this little machine). Thanks a lot
> Tony!

IIRC it's a very odd design electronically, in that the keyswitches
are not wired
as a matrix. Rather they are each wired between ground and an input of a 4051
multiplexer. I have no idea why it was done this way.

> But the stuck key appeared to be cause by the "plunger" (is that the
> correct english word?) is slightly cracked in the corner. When the keytop
> is inserted it is not sliding very well.
> I have not found a method of repairing it so I am asking the community if
> there are anyone that has spare "plungers" for the HP9816 keyboard.

I believe the same plungers were used on many other machines. I know for
a fact that a VT52 keycap will fit an HP9816 keyboard, so the plunger is
very likely to be the same as that machine. Other likely ones are VT100,
early TRS80 model 1, TI99/4A, HP85 (etc). That may help you find a scrap
keyboard to raid.


More information about the cctalk mailing list