Troubleshooting the B2 card connections causing the 1132 printer line spacing issue

DREW OUT THE NETS FOR EVERY PIN ON B2 AND B3

I used the ALDs and flipped through them in order to list all the other pins connected to each pin of B2 and B3. I will use this for two verifications - modifications detected by wire-wrap and broken connectivity. For both, I will pull all the SLT cards so that I don't see connections inside the cards, only traces or wire-wrap connections. 

LOOKED FOR MODIFICATIONS

I followed all the yellow IBM wire-wrap to the destination pins to see if they indicate that my ALD is not an accurate representation of this board. If this uses an alternative assignment of gates and different wiring, it will complicate things immensely.

Fortunately, this did not seem to be the case, as far as everything I could check with the wire-wrap on the board. Any modified traces are much harder to spot. 

LISTING ALL CONNECTIVITY BREAKS DISCOVERED

I found quite a few pins that did not have full connectivity to all their peers in the net. In some cases, the net had been subdivided, with several pins in one group and one or more in a second. This reduced the number of connections I had to add to the backplane. 

It appears that we mainly have broken connections between B2 and all the other cards. The signals that seemed to be broken appeared to be vertical traces on the backplane. This suggests that this corner of the backplane suffered trauma, perhaps just at the card socket, which severed quite a few connections. 

Possible sign of glass fracture on this side of backplane at B2

I checked the connectivity of the adjacent cards at B3, C2 and C3. These were all fully connected as they should be. I ran out of time due to a satellite launch this evening that I am working, as there are a few more adjacencies I need to test. Namely the top cable connector that spans over the B column, as well as the A2 cable connector to the right of the damaged card slot. I had tested all the links from A3, below it, over to C2 and C3, so the odds are that most are still good. Still, this should be verified before I resume testing. 

WIRE WRAP CONNECTIONS ADDED TO RESTORE LINKS BETWEEN B2 AND OTHERS

I added wires to restore all the nets. Unless I find other issues with the top cable connector or socket A3, I believe I can go back to more traditional debugging with this issue behind me.