HP262x keyboard voltage

[Tony Duell]

> 
> And using a 2392A keyboard ?

 I don't think I have one of those. What machine does it go with?

> It also uses the HP150 keyboard interface..
> The original keyboard looks a lot like the small HP 9816 keyboard..
> Maybe you could modify one of those.

No, the HP9816 keyboard is very different. it's a 5V interface on 4 wires 
(+5V, ground, clock, data (from keyboard)/reset (to keyboard). It also 
has the twiddleknob (which is addressed as 1 column of keys -- 7 bits of 
motion and 1 of direction IIRC).  Interestingly the 9816 keysiwtches are 
not wired as a matrix, rather one side of each switch is grounded, the 
other goes to a multiplexer input. Scheamtics are on hpmuseum.net.

The closest keyboard i have electrically is the HP150 one. It is the same 
interface, similar circuitry, but with differnt key matrix layout. I 
think I can hackl that by replacing the scan counter chip in the keyboard 
(a 4024) with a little circuit of about half a dozen chips. 

The closest keyboard I have for having the right keys is the one for the 
HP2623 terminal -- after all a similar keyboard was used on the HP125, 
which as you know is a very similar machine to the HP120 (to the extent 
that the firmware ROMs are the same, for example). Of course the 
interface is quite differen, but a conversion circuit shouldn't be too 
hard to buiold (probably cost more for case/connectors than for logic 
chips!).

-tony