How old is the machine ?
Maybe its an SCR drive that runs off the AC directly. There is no big DC powersupply.
SCR drives chop the phases of the AC directly. As the AC crosses the zero crossing point the SCR turns off.
SCR drives are tough, but not as smooth and precise and a PWM drive.
Good luck with that DSPMC. Ethernet with cnc can be a real pain. Just look at the Grex. If the Grex had been USB, i bet it would have been a success.
Larry K
Manufacturer of CNC routers and Viper Servo Drives
www.LarkenCNC.com and www.Viperservo.com