GE Senographe Essential: intermittent gantry CPU board lockup
What happened
The system intermittently froze: it stopped responding to buttons and pedals, red LEDs DS12 and DS13 lit up on the gantry CPU board, and the row of yellow LEDs stopped blinking. No error codes were shown.
What was checked
- Find the LED legend for the CPU board to interpret DS12/DS13 and the stopped yellow LED row.
- Measure the supply rails on the board (reported as 3.3 V, 2.5 V and 1.9 V in the case).
- Watch the CPU supply voltage with an oscilloscope to catch dips and dropouts.
- Check the operation of the 5 V-to-2.5 V buck converter.
Cause
In this case the processor was under-supplied: instead of 2.5 V it received an unstable 1.8 V. The fault was traced to the 5 V-to-2.5 V buck converter, whose output sagged and dropped out — a picture consistent with degraded solder joints on the converter and on the resistors that set its output voltage.
What was done
As reported, the board was repaired by resoldering: the pins of the buck converter and all resistors in its voltage-setting network were reflowed; chip reballing was also mentioned in the case. The lockups did not return afterwards.
Safety
Before any soldering on the board, isolate the unit from mains and confirm the supply capacitors are discharged, and after any power-circuit repair complete the manufacturer's electrical safety checks before returning the mammography system to clinical use.
Lesson: When a controller board locks up intermittently, check its supply rails with an oscilloscope before condemning the board — an unstable buck converter can mimic a processor failure.
Covered in the course: Mammography 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.