15 Dec
2015
15 Dec
'15
5:32 a.m.
Solder side pic sent to your email! Thanks!
On Dec 16, 2015 2:22 AM, "Brent Hilpert" <hilpert at cs.ubc.ca> wrote:
On 2015-Dec-14, at 2:02 PM, Mike Ross wrote:
- 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've just spent a few hundred bucks with one of the few mechanical
Selectric gurus left standing - a local guy here in NZ who did an
amazing job, several broken and seized bits fixed, the mechanism is
now like new and works perfectly in typewriter mode - so it's going to
end up working, one way or another!
Well, I vote for doing a little more work to get it working as is.
If it's all there, it 'should' work as intended and really doesn't look
to
be very complex.
Chances look good it will be adaptable to a centronics port.
Pin 9-11 & 21-24 connect to the pull-up resistors and head in the the
direction of the 7475 DFFs - that's likely the 7 data bits.
Traces from the DFFs look like they then head to the proms which are
likely 3 * 256*4.
That leaves 13,17,19 for some combination of control signals such as
print-strobe-in, ready-out, fault-out.
I notice there is an MC14490 hex contact debouncer there. You say this is
not a keyboard-send conversion, so I'd guess those debouncers may be
picking up mechanical contacts that indicate end-of-operation, to produce a
ready signal.
If reverse engineering really isn't your shtick, send along
reasonable-resolution photos of both sides of the board and I'll work on a
schematic.
Could do it with the photos you provided earlier except the solder-side
photo isn't complete.