回复：笔记本屏幕亮度突然变暗，是什么原因？

if you never change any parameters or use FN+downarrow you can follow:

1. unscrew screws in front of your LAPtop monitor
2.carefully open the the back cover ( definitely careful,because power wire and data wires connect both covers_)

3.open the shield foil
4.unplug power and data wires
5.you will find there are two long-light each side
6. check if anyone is burned by looking if the end of the light has been turned into black
7.change a new light