Solder side pic sent to your email! Thanks! On Dec 16, 2015 2:22 AM, "Brent Hilpert" <[email protected]> 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. > >
