Philips Intera 1.5: gradient racks trip right after start
What happened
After a gradient axis replacement the racks would not start: the power supply came up, the axes started and shut down immediately, a rack fault indication stayed lit for a few seconds, and no gradient dumps were produced; later the temperature sensor read -35 °C, as reported in the case.
What was checked
- Checked the gradient rack power supply — no faults found, as reported.
- Checked the door interlock switches.
- Analysed the BDAS logs — inconsistent temperature readings pointed away from the racks themselves.
- Inspected the heat exchangers and found a rodent-chewed temperature sensor cable with intermittent contact.
Cause
Rodent damage to the temperature sensor cable at the heat exchanger: the intermittent contact first made the sensor read falsely high, so the axes heated up without the overheat protection acting, and then read falsely low, which stopped the coolant pump and took the gradient down.
What was done
Repaired the damaged sensor cable, then waited for the fault indications to clear and for the system to warm back to about 20 °C before restarting; the racks and gradients then started normally, as reported in the case.
Safety
Before working inside the gradient racks, isolate the power and allow internal capacitors to discharge, check all cabling for rodent damage before re-energising, and complete the electrical safety tests before returning the system to use.
Lesson: A single damaged sensor can mimic a rack fault, so when racks drop out with no clear error, check the ancillary sensors and the cooling loop before digging into the racks themselves.
Covered in the course: MRI 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.