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|
|Wrapped with black electrical tape|
|Coil pressed back into place on the core|
|New leads soldered into place and continuity verified|
|Magnet 'bar' installed back on magnet assembly|
|Magnet assembly reinstalled on magnet unit|
|Armatures replaced on repaired magnet bar|
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!
SAC INTERFACE FOR ADDING PERIPHERALS TO THE 1130
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.