Nascom 2 keyboard connector

[Tony Duell]

> 
> 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

The Nascom 2 keyboard seems to use D0...D6 (in that the port is read, 
then ANDed with 0x7f). 

The '93 is the counter I refered to in my other message, the '145 is the 
decoder. I wonder what the other chips are for. It does use switches and 
not something more strange, I trust....

> > 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

Yes, that's what I do for things other than DB shells. One day I'll buy 
the DE one (which is the next most common size that I use). 

> 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? 

No, it's not the rack-n-pinion press. These punches work by a central bolt.

What you do is drill an 8mm hole in the middle of the place where you 
want the D connector. Bolt a template (supplied with the punch to that 
hole, then drill 2 3mm holes through it (these later become the mounting 
holes for the connector). Fit the 2 parts of the die to the panel -- they 
have pins that go through the 3mm holes. Fit the punch into the die with 
the bolt going through the 8mm hole. Fit the ball thrust bearing, washer 
and nut, then tighten the nut to pull the punch through the panel. 


As I said, if you want a DB hole done, and the aluminium is thin enough 
(see the spec on the RS web site, etc) I'll do it for you.

-tony