See a closeup picture of the Bosch servo drives and other cabinet
internals:

http://igor.chudov.com/projects/Brid...nside-Cabinet/

I traced some wires. Wires A1 and A2, so marked on the servo motor's
terminal, are power. Applying power from a separate DC power supply,
to them via contacts 4 and 6 on the main terminal strip, makes the
servo motor run. I only tried Y axis but it seems to work.

Wire number 4 is ubiquitous, like tarballs on the Gulf coast. Wire
number 4 is present on the servo transformer, goes to all servo
drives, and seemingly to all servo motors. (!)

I interpret it as some kind of "neutral", kind of like negative
ground, which applies to both DC and AC (since it comes out of the
transformer).

I will post some thoughts on the Bosch drives and such tomorrow. Time
to go to bed.

i