Mystery IC: Allen Bradley 314B102
tothwolf at concentric.net
Thu Dec 17 16:47:20 CST 2015
On Tue, 15 Dec 2015, Mike Ross wrote:
> On Tue, Dec 15, 2015 at 4:59 AM, tony duell <ard at 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
> 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:
> - 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
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.
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