Tek 4109 terminal

[Tony Duell]

> Minor problem, in that I found the keyboard's pretty hosed. It uses
> metal foil circles for the switch contacts; these are attached to the
> switch plungers via foam spacers which give he correct clearance and
> presumably help with the keyboard's feel...
> 
> Unfortunately it's the same stuff normally used for fan filters, and has
> totally decayed :-( 

Ah, a Keytronics keyboard.... and alas I know the problem well, as the 
keyboard on my PERQ 2T1 has suffered :-(.


When I get a round tuit, I think I should make some kind of cutting punch 
and stemp out 100 or so foam circles to fix the darn thing.... Or if you 
find a quciker way of doing it, let me know...

[...]

> Hmm... I suppose if the self-tests are mouse driven I can run the
> keyboard with no keys just for the purpose of testing the terminal
> though (and short pads where necessary to simulate keypresses)  Thanks

It's capacitive (not contacts). You'll discover the conducting layer is 
on the _top_ (foam-side) of the lower plastic disk, and doesn't actually 
short anything). My experience is that a finger placed on the pads 
provided enough extra capacitance to simulate a keypress...

-tony