ProScan 7000: detector arm not moving, images blurred with horizontal stripes
What happened
The detector arm stopped travelling, and images came out blurred with horizontal stripes, which pointed to the arm not holding position during acquisition.
What was checked
- Listened to the drive as it tried to run, to separate a motor fault from a mechanical one
- Inspected the drive gear on the stepper motor shaft
- Checked the linear bearing and rail, including the condition of the grease (heavy greasing in this unit does more harm than good)
- Reviewed a video of the mechanism in motion to confirm the diagnosis
Cause
The engineers found the drive gear had been seated incorrectly on the motor shaft: the locking screw was not landing in the shaft dimple, so the shaft was slipping inside the gear and the arm never actually moved.
What was done
The gear was re-seated on the shaft so the locking screw lined up with the dimple, the screw was secured, and the arm was run over its full travel — the unit was returned to service, as reported in the case.
Safety
Before returning the unit to use, run the arm through its full travel with hands clear, confirm no binding or pinch risk, check that guards and interlocks are intact, and carry out the electrical safety test.
Lesson: A stepper motor that hums but delivers no motion usually means a slipped or badly seated coupling — always check that the gear's locking screw actually engages the shaft dimple before replacing the motor or driver.
Covered in the course: X-ray Service — Level 2: Fault-Finding →
Written from an anonymised case shared by service engineers. It is not a manufacturer instruction and grants no authorisation. Independent note; names are trademarks of their owners.