Just done a little bit more probing while waiting for a job to finish.

There are 6 TEA3718S chips that obviously power the stepper motors, which receive 36VDC.

The other big smoothing capacitor measures at 12VDC.

One half of the motor switch controls a 5V feed from the control board, and the other is switching 24VDC. I never checked but one side seems to come/go via a TO package bolted to the main heatsink. It's possibly on the supply side, and is what is providing the 24VDC from the 36VDC.
There are a couple other chips bolted to the heatsink, which at first glance I thought were stepper driver chips given the number of pins, but given the row of TEA3718S's I'll need to have another look.