Replacing the head connector required excavation to determine the coil wiring; successful conclusion

DUG OUT THE CONNECTOR TO FIGURE OUT WHICH WIRES GO TO EACH PIN

I know from the documentation about the wires from the SLT card compartment out to the female head connectors. There is a violet and a grey wire that goes to the two read/write coils, a red wire that goes to the erase coil, and a black wire that was not covered anywhere else. That wire hooked to the ground pins on the backplane.

The diagram for the wiring of the heads does not show the fourth wire - the ground connection. The only mention at all is the table above. 

However, from the head to the male connector, there is no documentation. I could figure out the pins because the connector is asymmetric, with two pins close together on one side and the other two spaced further apart. However, if I was not able to solder the pins then I would need to make a new connection and for that I would need to know how to identify the various coil connections.

I picked away at the plastic molded connector to expose the ends of the pins that were broken off as well as expose enough of the wires connected to those pins that I could confirm colors. It is good that I did, because the four wires I found in the connector were red, blue, white and white. These don't match the colors from the female connector. 

I found nothing at all about the wiring in the connector in the documentation for the 2310 drive which is also the internal drive on the IBM 1130. However, the heads are quite similar to the multiplatter 2311 drive that IBM introduced at about the same time. I looked over some documentation on that drive and found the head wiring that matched my connector.

It shows the four wires connected, unlike the documentation for the 2310 drive. I made some resistance measurements across the four wires hooked to the upper head, which was undamaged. I found no connectivity at all through the black wire to any of the other three, while the diagram above implies there is. I checked to the female connector for the damaged lower head and that too had no connection from the black wire to the pin on the connector. I removed one of the female connectors and could see that there is no connection at all to the fourth pin.

It was apparent that the black wire, hooked to ground, serves only as a cable shield up to the female connector. No such ground shield exists from the male connector to the head itself. That means that in the excavated male connector I was repairing, the blue wire was unused on this end and could be ignored. 

It was a painstaking process to solder the pins back on the two active positions where they had snapped off. Once I was certain that there was good connectivity, I covered the connector with Kapton tape and reinstalled it on the machine.

I tested from the backplane pins for the same resistances and connectivity, ensuring that my reattached female cable had good wire-wrap connections and that the entire path to the coils in the head was intact. 

HEADS BACK IN PLACE AND A VIDEO OF THE ARM MOVEMENTS

You can just see the two holes on the left side above the top head and below the bottom one that had pivot pins inserted. These allowed head loading plates to be pushed down onto the backs of the heads in order to force them down to fly 125 microinches above the spinning disk surface. 

The video I took shows the drive spinning, finishing up the 98 second delay before you can hear and see the head load solenoid snap closed. The solenoid is near the bottom left in the video, you may have to watch a second time to spot it. That would normally close the two heads around the spinning platter, but for safety reasons this is not done on this drive.

I then moved the arm forward and back in continuous mode, then stepped it in both 20 mil and 10 mil step sizes. You can see the backsides of the two detents, one for even and one for odd tracks. When moving in 10 mil steps, the detents alternate, whereas with 20 mil step the same detent is re-engaged after each movement.