Yes there are three psu's, an 11A 36v for the motors and drive boards, a small 24v 1/2A one for the safety and control circuits, and a 24V 3A unit for the bob.

none of the negatives are grounded or commoned, unless done internally but I checked them with a meter from 0v to mains earth and all were isolated it seemed.

the bob is not commoned to the PC as the screen on the cable does not connect, the screen on the db25 plug is not connected to the 0v rail on the bob either, it has full opto isolated PC inputs.

the outputs are also fully opto isolated to the drive boards so no common needed there either.

the safety inputs are also opto but I threw in the relays as an extra measure to keep the low voltages inside the cabinet.

the safety circuit psu is just a little wall-wart that I threw in when I pinched the good psu for the bob, I could try using the bob psu but that would likely bridge the noisy circuit direct to the bob power supply lines and defeat the object of isolation. I will get another small psu and ditch the wall-wart now it's working.

cant think of much else to offer really, please do ask if you need more.

dave