I had to downsize the Arrakis mechanism slightly owing to an error in the sand box design for the table. After taking the XY mechanism apart, milling the frame pieces and reassembling, I tested it. It homed fine, so I pulled up one of the old patterns and ran it… for about 1 second…
The old pattern was for a larger table so the magnet carriage slammed into the end of one axis at full speed (1000 or 1500 mm/sec). The sudden stop caused the motor to pull huge current, forcing either the motor driver or the power supply shut down. All the energy stored in the motor had to go somewhere so it went back onto the 24V rail which let the magic smoke out of a voltage regulator chip on the Duet controller board and killed the power supply.
I tested the motors and they both seem to be OK as is the other power supply. I’ve ordered a new Duet board and power supply, and decided that in the interest of protecting the expensive controller board, I will power it from its own supply instead of putting it on one of the motor supplies.
If anyone is considering using servomotors, consider this a warning! Learn from my mistake!