Main LED backlight power rail. If 0V measured with power plugged in, check motherboard backlight SMD fuse (F1/F2).
Screen stays completely dark but image is visible under a flashlight? Read our detailed guide on locating and replacing blown SMD 0402/0603 backlight fuses.
Read Backlight Fuse Rework Guide βCheck if upgrading from your current panel to a higher refresh rate or higher resolution panel is electrically compatible with your laptop's harness.