Siemens MAGNETOM IMPACT: RF faults blamed on a missing reference voltage
What happened
The receiver reported a missing or incorrect reference voltage although the signal was actually present, and the RF chain behaved erratically. The boards showed electrolyte staining and the RFCI power supply outputs were low.
What was checked
- Checked the reference voltage the receiver complained about against actual rail values.
- Measured the RFCI power supply outputs; as reported in the case, they were low by roughly 0.3–0.5 V.
- Inspected the boards, including the MPCU Box area, for electrolyte leaks and checked the capacitors.
Cause
The engineers found electrolyte leaked from capacitors spread across the boards, and the RFCI supply outputs had drifted low; with some rails carried between boards through mounting standoffs, the undervoltage made the reference reading look wrong and destabilised the RF chain. This was one case, not a general rule.
What was done
The engineers brought the RFCI power supply outputs back to the specified values with the trimmer potentiometers, verified the rails under load, and confirmed the reference voltage reading and RF operation returned to normal; the case was solved.
Safety
Before opening the power supply, de-energise the cabinet and lock it out, and treat the electrolytic capacitors as still charged — verify discharge before touching anything inside.
Lesson: When a receiver complains about a reference voltage that is actually present, check the supply rails and look for electrolyte leaks — a drifted power supply can imitate a board or sensor failure.
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.