4 Jun
2005
4 Jun
'05
2:58 p.m.
On Sat, 2005-06-04 at 00:29 +0100, Tony Duell wrote:
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....
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 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?
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