A closer look at the spindle-servo today. Googling for the model number does not immediately yield a datasheet, although I found a few similar-ish model numbers. The high-power connector is simple with U, V, W phases, Protective Earth, and +/- terminals for the solenoid brake. The brake opens at 24V and 0.67 A. The back can also be opened but doesn't reveal much more than an October 2001 manufacturing date. Hooking the scope to U, V, W and rotating the shaft with an electric drill produces some nice sine-waves. I'm not at all sure about the pinout of the encoder-connector, but looking at pairs 1/2, 3/4, and 5/6 seems to give something that could maybe be a resolver?