How to determine the quality of the LCD screen

Posted by sere on December 10th, 2019

The liquid crystal screen referred to here refers to a liquid crystal panel, which includes internal row and column driving circuits. In actual maintenance, whether the LCD screen is damaged cannot be detected with common tools, and it is generally judged by inspecting its failure phenomenon. As for the failure phenomenon of LCD screens, there are two main categories: one is physical damage, such as bad pixels (bright or dark points) on the screen, black bands or broken screens; Problems such as flower screens, vertical bands, etc. Although the failure phenomenon after the LCD screen is damaged is very similar to some failure phenomena after the signal board or logic board is damaged, it is easy to see the slight difference if you look closely. Since the LCD screen is a terminal device for displaying images, the failure of the LCD screen has nothing to do with the current signal source and signal content, that is, it exists under the signal input state of TV, AV, color difference components, etc., and the failure phenomenon is the same, dark spots, The position of the black belt or vertical bar is fixed.

During practice, if you suspect that the LCD screen is faulty, you can first disconnect the power supply of the signal board and the logic board, that is, make the signal board and the logic board inoperative, and then force the backlight driver board to start, so that the backlight lights up. If there are still dark spots, bright spots, black bands, or vertical bars, the LCD screen can be judged to be damaged.