Siemens Somatom Emotion: host boots straight into BIOS after UPS swap
What happened
After a mains surge killed the workstation UPS, the engineers replaced it — and from then on the host computer went straight into BIOS setup at every power-on. Exited from setup, the system booted and ran normally; only the entry into BIOS was wrong.
What was checked
- BIOS load defaults and full reconfiguration — behaviour repeated on the next boot.
- CMOS battery replaced (reported in the case as measuring about 2.9 V) — no change.
- Full reset of the board: battery removed, capacitors discharged, settings restored from photos — the machine still went into setup.
- Physical inspection of peripherals: the engineers found a second PS/2 keyboard left connected behind the IRS, with the Del key stuck down.
Cause
Neither the UPS nor the CMOS was at fault. During POST the machine saw a constant Del keypress on that second keyboard and dutifully entered setup on every boot. The timing with the UPS replacement was pure coincidence.
What was done
Disconnect and remove the keyboard with the stuck Del key. The next power-on went normally to the operating system, and the problem did not return.
Safety
UPS and host work means live mains: isolate the supply before the swap, expect stored energy in UPS capacitors even when unplugged, and complete the electrical safety test before returning the system to clinical use.
Lesson: Before blaming the board after any change on site, rule out the obvious: a stuck key on any connected keyboard — including one you did not plug in yourself — will send a machine into BIOS setup at every boot.
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.