Mystery IC: Allen Bradley 314B102

Tothwolf tothwolf at
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> 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: 
> - 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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