Siemens Harmony: STIMO and PALI tests fail at system start
What happened
At system start, every block in the MR Scanner view reports OK except STIMO and PALI — both tests fail.
What was checked
- Run the PALI function test from the service software to verify SAR-limit detection.
- Check the reported indications: CLK_20 LED on RX4, STAT LEDs on MC4C40 and MC1C40, and the RFPA_ON signal.
- Check the actual gradient currents in the online monitor.
- Reboot the system with no coils connected.
- Unplug, inspect, clean with alcohol and re-seat every coil connector, checking the contact condition.
Cause
In this case the engineers found the probable cause to be loss of contact in the coil connectors, which made the PALI and STIMO tests fail on an otherwise healthy system.
The cause is probable and was not fully confirmed.
What was done
First reboot the system with no coils connected; if the tests still fail, unplug, clean with alcohol and re-seat all coil connectors, checking each contact. The outcome in this case was reported as probable, not confirmed.
Safety
An MRI magnet is always energised: use only non-ferromagnetic tools near the bore, put the system in a safe off state before unplugging coil connectors, and confirm normal operation before returning the scanner to clinical use.
Lesson: When SAR-monitoring and stimulation tests fail on an otherwise healthy scanner, check the simplest interface first — the coil connector contacts — before suspecting the RF chain.
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.