Troubleshoot Open Armature Circuit

If one axis doesn’t move, but you can see the position counter changing in Jog-1, the motor armature circuit might be open.

To quickly determine if the motor is bad, set servos off, disconnect both motor cables at back of control, and connect the bad axis motor cable to the good axis. Jog the good axis: if the bad axis moves, the motor is good and the issue is in the control.

If the armature circuit is 'open', the motor terminals on the servo amp will be about the same as the bus voltage.
Here's how to check that:

• Set servos off, reconnect motors, then set servos ON.
• Measure DC volts at motor terminals on the bad axis: if it is 60 to 70VDC, the armature circuit is open.

Examine the illustration below:

• Tug on the red and black wires that go through the connect card; they should not pull out. (Check both axes to compare)
• With servos on, measure DC volts across the thermal overload; it should be near zero volts; if not, replace the overload. (Check both axes to compare)
• Measure between the armature relay and top of overloads as shown in image below (for Z-axis armature relay pin 8 and inboard overload; for X-axis armature relay pin 5 and outboard overload). Voltage should be near zero volts; if not, replace the relay. (Check both axes to compare)