Nascom 2 keyboard connector

[Jules Richardson]

On Sat, 2005-06-04 at 00:29 +0100, Tony Duell wrote:
> My Nascom is almost impossible to get to at the moment, can you remind me 
> as to what chips are on the keyboard? I am going to guess at at least one 
> TTL decoder chip, and maybe not a lot else.

4 x 7400 ICs, 2 x LM3086, then a 7493, 74123 and 74145.

Hmm, that's interesting. That's the exact same chips as on the Nascom 1
keyboard (which only uses  6 data lines, amongst other things. I'll
definitely trace as much of a schematic as I need to I think as maybe
the Nascom 2 keyboard doesn't use 8 data lines either (even though
they're all present on the CPU board's connector)

> I did find my schematic for the Gemini keyboard last night (this is a 
> much larger system using the same NASbus pinout, etc). It is, alas, 
> very different, the Gemini keyboard has a microcontroller in it, and 
> seems to send ASCII to the rest of the machine.

Aha, yes we have one of those at the museum - long time since I've
peeked inside, but I seem to remember it was a pretty tricked-out
system. 

> > needed by the keyboard itself, I'll move it to the CPU chassis and use
> > DA15's for the keyboard.
> > 
> > If it is needed, I'll have to go the DB25 route. I did wonder about DA26
> > connectors, but I'm not sure if those were about when the Nascom 2 was
> > current (I'm trying to use period bits for everything). Plus I don't
> 
> Strange comment, based on your attitude to the 5155 :-)

Don't start that again ;-)

> > Cutting out the right shaped holes in aluminium for these connectors is
> > a right pain in the butt, so I don't want to have to do it more than
> > once ;)
> 
> RS do some very expensive hole punches for the D-series connectors. 

Hmm, be nice to have one of those one day. In the past I've used steel
mounting brackets from PC expansion cards that have the right connector
hole as a template for cutting aluminium. Clamp them over the piece of
work, then remove as much material as possible with a drill / snips
before finishing off with a set of files. It works pretty well for
putting the right holes in aluminium, just takes a while to do a nice
job where a proper tool would be more or less instant.

Presumably the punch tool has a limit as to how far from the edges of a
piece it can reach? 

cheers

Jules