On Tue, 15 Dec 2015, Mike Ross wrote:
On Tue, Dec 15, 2015 at 4:59 AM, tony duell <a...@p850ug1.demon.co.uk> wrote:
This board does not look that complicated and all the ICs have known
numbers on them (mostly TTL logic). If it were mine I'd trace out the
schematic.
That's true and possible. I'm in two minds on this thing:
- intention was to rip all this out and convert it to a full I/O serial
terminal, using an Arduino-based setup that Lawrence Wilkinson has
already built and tested:
https://www.flickr.com/photos/ljw/sets/72157632841492802/with/9201494189/
- all the keyboard contacts are already in there, Western I/O just cut
the IBM wires off when they ripped the IBM guts out and converted it
printer-only. I'd like to figure out the interface that's presently in
it, just to check out the mechanism, and for that 'ah ha!' moment :)
- but I don't want to spend any significant time on it if I'm just going
to rip it all out.
- but, although the Western I/O conversion 'butchered' a perfectly good
IBM 2970, it IS a rare representative of that era, when all kinds of
Selectric conversions were commonplace. So perhaps, as a nod to that
era, it should be left as-is, as a preserved example? What say people?
I've seen posts on old lists where people have referred to buying these
back in the day - converted Selectrics I mean - and seeing 'mountains'
of them in warehouses. They were once common. Where have they all gone?
Is mine the *only* survivor from those mountains of 3rd-party backstreet
conversions? Does anyone else have any?
I have one of these print-only IBM Selectrics that I got along with a
TRS-80 model 1 which may very well be one of these modified IBM 2970
Reservation Terminals. It was interfaced to the TRS-80 via a "Micromatic
80" interface connected to the computer's parallel port. From what I
remember, it has both a serial and parallel input and has a third
connector which the Selectric connects to using a card-edge type
connector.
The Micromatic 80 itself seems to mainly be made of 7400 series logic
chips but may also have a few proms.
If there is sufficient interest, I could strip the parts from the
interface board and scan the bare board (double sided). It is already in
my to-do project queue anyway as I was planning to replace the 3 edge wipe
IC sockets (most of the ICs are soldered directly to the board) and the
original aluminum electrolytic capacitors.
