Connecting to the PDP-7

Two 55-pin connectors are available on the PDP-7 SN129. One provides 18 bits of output data, and the other can read 18 bits of input data.

My project was to solder 50-pin ribbon cables to the 55-pin connectors. This will allow us to easily connect to external logic.

55-pin round connector
Pin numbers spiral in, so it is best to begin soldering at the inside and work out. Here are the first four pairs of wire. The green wire is the 25th pair of the ribbon cable.

Each wire has heat-shrink tubing to both insulate and to provide structural strength.

55-pin round connector
This is the other connector, and being of the other gender it spirals the other direction. The final two wires are ready to be soldered.