Repair of DELL 3421 laptop screen with dark screen and unlit backlight

Repair of DELL 3421 laptop screen with dark screen and unlit backlight

1 pin EN is normal, 23 pin Vin has no voltage to ground resistance of 0 ohms. After tracing forward, it is found that a current limiting resistor is burned, and a small capacitor is short-circuited behind the current limiting resistor. Find a small resistor of 10 ohms and a small capacitor, and the boot is normal.

Machine model: DELL 3421 notebook

Malfunction: the notebook screen is dark.

Maintenance process:

A DELL 3421 notebook, the fault is that the image is normal, and the backlight of the dark screen is not bright.

The dark screen was tested by changing the screen first, and the screen was disassembled. It was found that it was a 140-mouth thin screen, and then a ASUS 15.6-mouth test was carried out. It can light up normally, and it can be judged that the screen is broken.

DELL 3421 Notebook Screen Dark Screen Backlight Maintenance Figure 1

Screen model.

DELL 3421 Notebook Screen Dark Screen Backlight Maintenance Figure 2

Dismantle the machine, measure that the backlight power supply insurance is normal, and the backlight turn-on signal is also normal.

DELL 3421 laptop screen is dark and the backlight is not on. Maintenance Figure 3

1 pin EN is normal, 23 pin Vin has no voltage to ground resistance of 0 ohms. After tracing forward, it is found that a current limiting resistor is burned, and a small capacitor is short-circuited behind the current limiting resistor.

DELL 3421 Notebook Screen Dark Screen Backlight Maintenance Figure 4

Find a small resistor of 10 ohms and a small capacitor, and the boot is normal.

DELL 3421 Notebook Screen Dark Screen Backlight Maintenance Figure 5