There are six wires coming from the 1130 that are plugged into terminal blocks on the front of the 13SD internal disk drive. Four of them are hooked to the Run/Stop (or disk power) switch that sits just below the entry slot on the front of the disk drive. The other two run to the main 1130 console panel to drive the Unlock lamp which informs the operator that the drive is at a stop, thus permitting the handle on the entry slot to be opened so that a 2315 cartridge can slide in or out.
The wiring schematics for these are divided across two different ALD (automated logic diagram) manuals, one for the 1130 and one for the 13SD. Sadly, the documentation does not align so that a reasonable person can determine how to connect them.
In Vol 4 of the 1130 ALDs, page ZB101 shows the six connections but refers them only to page XA101 of the 13SD ALD. The names given on page ZB101 are:
- 48V Ground
- -Start File Motor
- -Head Load Sw
- -File Latch
These line up well with page ZK111 of the Vol4 1130 ALD where those four connections, by the same names, are linked to ZB101.
On page XA101 of the 13SD ALD, four of the six names do not exist at all on the diagram. Only 48V Ground (TB3-A-1) and +48V (TB3-3) exist.
This diagram is drawn for the use of 13SD drives in an IBM 2310 cabinet, with some footnotes referring to 'other systems' such as the 1130. One of the footnotes says that the actual circuitry in the dashed area on the left is drawn in ZB101 for the 1130 system. It is not!
I worked out that the four missing signal names are in this portion of XA101 above:
The Disk Unlock lamp is hooked to a 200 ohm resistor tied to the cartridge unlock solenoid. Signal -Start File Motor is TB3-8 which runs through a couple of safety microswitches to the coil to energize relay K1 and start the motor. The microswitches check that a cartridge is inserted and the handle is in the closed position.
Signal -File Motor Latch On is wired to TB3-7, which goes through contacts on the start relay K1 to TB3-8 so they are only active when the start motor is already energized. Thus it holds the start relay on until something interrupts it. That something is the switch that shows the disk heads are loaded, -Not Head Load Switch, which is grounded when the heads are down but opens up to interrupt the start relay when the heads pop up. The heads can come up in conditions such as if the speed gets too low or some other error is discovered causing the drive electronics to release the head load solenoid.
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