Philips Brilliance 16: no warm-up or scans, rotor spins endlessly without X-ray
What happened
As reported in the case: after a RHOST swap with the original CPM left in place, the scanner would not run tube warm-up or studies. The warm-up countdown ran without the tube ever firing, or initialization never finished; later the rotor spun continuously with no X-ray. Manual exposure, both stationary and rotating, worked without complaints. The logs were missing the usual normal-completion entries, and the ScannerShell log was flooded with RetZPos errors.
What was checked
- Re-flashing the RHOST board and restoring a host backup — no change.
- Inspection of slip ring contact surfaces and brushes — nothing suspicious found.
- Reading the 7-segment status indication on the RHOST board.
- Key observation: manual exposure, stationary and rotating, worked fine — pointing away from the host software and toward the rotor position feedback hardware.
Cause
The engineers traced it to a faulty spindle block: rotor position feedback was unreliable, so the system never received proper position confirmation and blocked warm-up and scans, while single manual exposures could still pass. The RHOST replacement had drawn attention to the wrong board.
What was done
Replacing the spindle block cleared all the symptoms. The re-flash and backup restore had not helped, and the newly fitted RHOST turned out to be serviceable.
Safety
Before opening the gantry, isolate and lock out the drive power and confirm the rotor has come to a complete stop — the rotating frame stores considerable kinetic energy, and spindle work should only be done by authorised personnel following the manufacturer's service documentation.
Lesson: When manual exposure works but sequenced scans hang with rotor position errors, check the rotation feedback hardware such as the spindle block before blaming the board you just replaced.
Covered in the course: CT 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.