Italray Tomo BT (HF650 Pixel): no high voltage, no anode spin-up
What happened
The system gave no high voltage and the tube anode would not spin up. On the generator board the READY and ROT.ERR LEDs were lit, together with the anode rotation protection LED D8.
What was checked
- Continuity check of the wiring and a check of all fuses in the rotation circuit.
- Resistance measurement of the tube stator windings — reported in the case as roughly 80/59/30 ohms.
- Voltage measurement at the spin-up stage: the GRID-SHIFT, GRID-MAIN and GRID-COMMON lines each showed about 189 V in this case.
- Confirmation that filament pre-heating was present.
- Check of the Prep/X-ray indication using the test button on the generator board.
- A clamp-meter current check of the rotation circuit was proposed as a next step.
Cause
The engineers found a poor contact on one relay pin on the anode spin-up (stator) board: with the supply voltages present, the pin was not making reliable contact, the rotation protection flagged a fault and the generator would not go to high voltage.
What was done
The engineers restored reliable contact on the relay pin of the spin-up board. Anode rotation and high voltage came back, and the case was reported as solved.
Safety
Before opening the generator, isolate it, allow the internal capacitors to discharge and verify absence of voltage before touching the boards; before the unit returns to use, carry out the electrical safety tests, and make any test exposures only with the controlled area clear of people.
Lesson: Normal stator resistances and correct supply voltages do not rule out a contact fault: a single bad relay pin can stop the anode rotation chain and, with it, the high voltage.
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.