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Lenovo B470 laptop screen flashing repaired
Machine model: Lenovo B470
Main board number: A47 MB 10250-2 independent display
Description: The laptop screen flashes, the screen flashes when the logo is displayed on the computer, and it also flashes when entering the system welcome interface, and there are traces of water damage.
Maintenance process: The problem can be roughly determined, and it should be backlight failure. There are traces of water damage corrode when disassembling the machine, but it does not affect the work of the machine, and the fault of scrubbing the motherboard remains the same. The oscilloscope catches the screen line backlight EN, and when you see the waveform below, you can clearly see the signal fluctuation.
Lenovo B470 laptop screen flashing repaired Figure 1.
Lenovo B470 laptop screen flashing repaired Figure 2.
The viewing signal source comes from EC control, direct line change, and screen backlight EN directly pulls screen VCC EN.
Lenovo B470 laptop screen flashing repaired Figure 3.
Lenovo B470 laptop screen flashing repaired Figure 4.
To prevent the white screen phenomenon at the instant of startup, skip the screen VCC directly over the 3V VCC of U4901 chip short-circuit S0, and the maintenance is finished.
Lenovo B470 laptop screen flashing repaired figure 5.
