Replacing bad heads on Diablo 31 to use for archiving IBM 1130 disk cartridges - part 2

MARKING POSITIONING OF HEADS ON THE DIABLO MOUNTS

In order to get the geometry of the head aligned with the drive properly, I marked the outline of the crashed heads on the metal holder that inserts into the Diablo arm mechanism. This will ensure I can get the replacement heads tightened down exactly where the original heads sat. 

Damaged head on right, attached to Diablo arm

REMOVING HEADS FROM 2302 ARMS

The screws mounting the heads to the 2301 arm have epoxy over them to protect them from unloosening accidentally. It was easy to chip the epoxy away as it is brittle. The screws were then removed and the head disconnected from the connector at the end of the 2302 arm. This is a very different connector than the one used on the IBM 1130 or Diablo drives. 

MOUNTING AND CHECKING OUT HEADS

I put the replacement head on the Diablo mount, with the screws slightly loose, then maneuvered it until it exactly matched the outline I had scribed from the original head. Tightening this up gave me a Diablo mount with a serviceable head. I will put epoxy on the screw, just as IBM had, to lock it down. 

Heads swapped, bad one loose on right

SWAPPING SIGNAL CONNECTOR 

I had to cut the connector off the crashed head and splice it to the wires from my replacement head. I needed to determine where each wire was connected inside the metal head. The read/write head has three wires connected to it plus a ground wire that provides shielding for the cable. Grey and Violet wires are connected to the two sides of the read/write coil, with a red wire hooked to the end of the erase coil. 

wiring as shown on 2310 document

The center tape of the three windings seen above are carried on the fourth wire that was attached on the 2302 arm. I looked at the use of the heads on 2311, another drive that utilizes the part and for which I have documentation.

Head wiring as used on 2311

I believe that the 1130's grey and violet wires are the two white wires from the diagram above, with the blue wire unconnected when used on an IBM 1130. The cable running through the disk drive, from the connector down to the drive electronics, uses the black wire for shield grounding but the black wire is unconnected to the heads. 

This gave me the information I need to splice the connector from the bad head with the wires from the good head. I will make the connections to give the same length to the cable as it had with the bad head, so that the cable routing and hold-downs in the Diablo would be good.