Landwind Mirror 2 HD: “No signal” on both monitors
What happened
Both monitors showed “no signal”; occasionally the unit started with heavy image artifacts and the picture dropped out again within 5–10 seconds, as reported in the case. The 3 V rail at the main board power connector sagged from 3 V to 1.8–2 V about 15 seconds after power-on.
What was checked
- Measured the 3.3 V, 5 V, 12 V and 3 V rails from the PSU and checked the status LEDs on the board; the engineers found the 3 V line collapsing under load.
- Probed the DVI differential pairs with an oscilloscope to check whether one of the three channels was missing.
- Cross-checked test points and nominal voltages against the service manual.
- Checked the EEPROM and flash BIOS on the COM Express module.
Cause
The engineers found two combined defects in this case: a degraded on-board 3 V power line that sagged under load, and failed BGA solder balls on two chips of the COM Express module (the mini board carrying the video path). The weak rail explains the drop-outs; the bad BGA joints explain the artifacts on the rare good starts.
What was done
Installed a DC-DC converter stepping 12 V down to 3 V to feed the main board instead of the sagging line, and re-balled the BGA on the two affected chips of the COM Express module. Per the case, the system has been running continuously since the repair.
Safety
Disconnect the system from mains and let the PSU capacitors discharge before any soldering on power rails, work with ESD protection, and complete an electrical safety test before the unit returns to clinical use.
Lesson: When a rail sags only under load, measure voltages a minute into operation, not just at power-on — and intermittent video from a COM Express module can be a solder joint fault rather than a dead chip.
Covered in the course: Ultrasound 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.