With the power supply schematic mostly done (I need to make another pass through to check that I got everything right), I decided the power supply needed a new input plug.
The power supply came with a two prong plug and a smaller two prong socket for power input. At some point someone had soldered a regular two prong power cord to the plug, which I quickly removed (mostly to get it out of the way).
The smaller socket (the round one on the right in the image below) looked like it might have been something standard decades ago, but didn’t look like anything I recognized.
The plug and socket both came out, and I dug out an old three prong power cord from the junk box. After spending some time figuring out how to connect things, I wired in the power cord.
Inside I used a terminal block to connect the power cord with the wires that used to run from the original plug.
Ground on the power cord got tied to the chassis, while the neutral line went straight to the transformer, and the hot line to the power switch.
Plugging it in and pushing the power switch made the transformer produce the characteristic buzzing sound, but it looks like the power indicator lamp is burned out. 23.2 V AC measured on the output of the transformer, which seemed reasonable. No smoke released, which is a good sign.
Now that I can get power into the power supply, I can start figuring out what works and what doesn’t.