Canon/Toshiba Aquilion: XC error at power-up with false 'tube 100%' reading
What happened
After the consoles were powered on, the system raised an XC error (at first mistaken for FC) and blocked scanning. After a reset, the tube temperature indicator started at 100% ('fully hot'), then gradually 'cooled down' and scanning was allowed again. The same pattern repeated at every power-up.
What was checked
- Confirm the exact error code from the system log — in this case XC, not FC.
- Notice the telling pattern: the tube temperature restarts from 100% after every reset and 'cools' while running — the tube's heating history is not being kept between power cycles.
- Measure the backup battery of the tube timekeeper, the module that stores tube thermal history; in this case it read about 0.3 V, as reported.
Cause
The engineers found a depleted backup battery in the tube timekeeper: with no battery, the module lost the stored tube thermal history at each power-down. After a reset the system started from a false '100% hot' tube state and recalculated it as cooling, which is why the scanner seemed to recover — until the XC error appeared again at the next power-up.
What was done
The timekeeper module was replaced, followed by filament current calibration — a procedure from the manufacturer's service documentation, done by authorised personnel. After that the XC error no longer appeared and the tube temperature indication behaved normally. Outcome: solved in this case.
Safety
A CT tube carries high voltage and a large reserve of stored heat, and after timekeeper work its real thermal history is unknown — let the tube cool, verify self-tests and interlocks, and complete the manufacturer's verification and electrical safety checks before returning the scanner to clinical use.
Lesson: A tube temperature that resets to '100% hot' after every power cycle means the thermal history is being lost — check the timekeeper's backup battery before chasing generator or cooling faults.
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.