Slow work wiring Signal Conditioner (Sledgehammer) into the disk signals for Virtual 2315 Cartridge Facility

WIRING FIVE SIGNALS THROUGH THE SLEDGEHAMMER

The Signal Conditioner, AKA sledgehammer, will clean up signals coming from the Virtual 2315 Cartridge Facility (V2315CF) through a cable of twisted pair wiring into the logic gates of the IBM 1130. Five of the twenty signal pairs passing through the cable are the priority for conditioning.

These are the -Sector Marker, -Write Clock Phase B, -Read Clock, -Read Data, and -Access Ready signals. The twisted pairs are wrapped with cloth electrical tape to form a cable which runs between the swing out logic gate A of the 1130 processor and the internal 2310 disk drive that fits inside the 1130 cabinet. 

The V2315CF intercepts the signals running over that cable, thus there is a 2310 Interface Board that this cable plugs into rather than into the disk drive. That interface board also has a cable coming from it that plugs into the disk drive. The main unit of the V2315CF will pass certain signals along between 2310 and 1130, but will generate others rather than using the signals coming from the 2310. 

The cable going into logic gate A fits into an SLT card slot in compartment C1. Each SLT card slot is a 2 x 12 set of pins with four of them reserved to carry power and ground for an SLT card. The remaining 20 pins deliver signals into and out of the compartment, in this case between the compartment and the interface board for the V2315CF. The pins on an SLT slot are labeled D02 to D13 for one column and B02 to B13 for the other column. For example, the signal -Read Clock is assigned to D02. 

SIGNAL TONE TRACER NOT USABLE

I tried to use a signal tone tracer, injecting the tone into the signal pin that I wanted to locate, then touching the probe to each wire pair to find the one with the loudest signal. Unfortunately, I couldn't set any level that would let me aurally distinguish the correct pair from the others. Enough tone is coupled through the ground wires that are part of each twisted pair so that every wire pair has almost equal volume. 

VISUAL TRACING FROM CONNECTOR WAS HIT OR MISS

I attempted to spot each wire pair coming from the connector, cutting the signal wire so I could wire in the lines to the Signal Conditioner. About half the time, the wire pair I thought was correct was not and I had to repair the connection by soldering the wire ends and using shrink wrap to insulate the joint. The design of the connector is not conducive to easily spotting the right wire.

Once I do find the proper wire for a signal and cut it, I have to solder on a twisted wire pair segment to each end of the cut. One of the new segments runs to the Signal Conditioner board input, where the signal coming from the V2315CF is injected. The other new segment runs from the Signal Conditioner board to the wire end that is running into the 1130 logic gate. 

When the new twisted wire pair segments are soldered on, their ground wires need to be connected together and to the ground wire of the original cable. The far ends of the new segments get a Molex KK pin crimped on and then they are inserted into five position connectors that fit onto the input and output of the Signal Conditioner board. 

CRIMPING WAS ALSO A PROBLEM AS MY CRIMPING TOOL WAS SUBOPTIMAL

Fastening the pins to small gauge stranded wires with the crimping tool I have in the shop was an exercise in frustration. The tool is not very good, thus the pin would often twist out of position as I attempted the first crimp, or bend one of the tabs outward instead of atop the wire or insulator. Others would appear to be properly crimped but not tight enough to hold the pin on for long. 

I ordered a better crimping tool designed for these pins and able to produce solid connections on the ten pins that are needed for the Signal Conditioner. Once it arrives I will finish up the construction.