Monday, March 9, 2015

1132 Printer restored and fully operational, more wiring of circuit interface cards for SAC interface box


I attempted to solder new wires to the connection points, to yield leads with continuity through the coil that can be soldered onto the main connectors on the magnet bar. This was easily accomplished and continuity verified before moving on.

New leads added to connection points inside coil
The coil had to be wrapped with a new protective layer to replace the wound plastic fiber that I removed to get to the connection point. I chose to use black electrical tape in narrow strips - after first covering the two connection

Wrapped with black electrical tape
The newly repaired coil was pushed back into place on the core and the leads soldered into place. With that done, it was time to begin reassembly. The magnet bar went on the magnet assembly. That in turn was placed on the magnet unit, then the armatures for the repaired bar was reinstalled. I tested each armature to make sure it was moving the levers that would release each cam clutch to print that column.

Coil pressed back into place on the core

New leads soldered into place and continuity verified

Magnet 'bar' installed back on magnet assembly
 The wires from the printer electronics were reconnected to the repaired bar. The magnet unit was slid back into the printer and tightened into place. It all looked good.

Magnet assembly reinstalled on magnet unit

Armatures replaced on repaired magnet bar
With that done, it was time to test the printer. I give myself an A minus grade, because while column 60 is now printing perfectly, column 3 wasn't. I felt the armature and discovered that something was binding. Should be a simple matter of pulling the magnet unit out slightly and then reinstalling it.

Doing a happy dance about the printer, even with the tiny bit of work left. I then loosened the unit, tightened it up again, and verified full correct printing on all 120 columns. I have put the doors back on the printer and will check this one off of the list of restoration projects!


Today I continued wiring the new circuit cards to the 160 pin connector, targeting that all 77 signals are handled by the interface cards. The new FPGA will be connected to the four interface cards using the headers on the cards and the FPGA board, making use of ribbon cables for neatness and signal control.

The interface cards convert the voltages, thresholds and currents of IBM's SLT logic to 3.3V CMOS signal levels for use with the FPGA. Further, they match the SLT circuits well in terms of impedance, thresholds and other characteristics, modeling the circuits implemented inside the 1130 at the other end of the 160 pin cable.

I completed the wiring of boards 2 and 4. I skipped over board 3 because the last board sits on the bottom of the stack, had only five twisted pairs to connect and that would make the task of restacking boards 3, 2 and 1 much easier. Wiring these boards is laborious, requiring me to verify every pin connection is going to the proper circuit on a board, then collecting and soldering the 24 ground wires from the twisted pairs onto a ground bus wire for the card. 

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