Current status: It worked! And then some 30-year-old internal connectors disintegrated. We have replacements that need to be soldered on. Limit switches have been replaced, and all limit switch connections and motor wires must be buzzed out down to the source to double check good connection. Anyone is welcome to do this if they feel they are competent at electronic repair, but please keep good organisation of bolts and where things go, and completely put robot back together again before the end of the day. This arm is still in great shape, and we aim to keep it that way!
Software-wise, there is a Raspberry Pi built into the controller. Plug an ethernet connector into its ethernet jack on the back of the box, and then plug the main box into AC power. Everything will start up, and then the Pi will be visible on your network.
SSH into it using credentials root / dietpi Once in, immediately type minicom –device /dev/ttyUSB0
You are now logged into the machine! Type help for some commands, but the main robot is controlled using Advanced Control Language. The reference for this is easily found online. With the current dodgy connections, homing the robot is a bad idea.