I worked in an LCD module factory. The monitors use letters to represent the quality of the screen. S is the best, A has no bright spots, the next one is B, the next one is D, and the next one is R for defective products. After repair, it will be F. It is normal to scrap less than 3 pieces, but bright spots are different from bright spots. Foreign matter, if there are bright spots in any screen, it is foreign matter, and the factory will judge it as defective grade D, which is the worst. Also, when you buy it, press the screen with your hands. Some of the finger pressure lines may be missing. You can see most of the defects under the black screen. Look at it at a 35-degree angle, and at a 45-degree angle to the left and right to see if there is uneven exposure. , light leakage, etc. Below I will talk about some defects in the factory: SLINE GLINE SSHITE GGHITE Acupressure line short of wire foreign matter light leakage. These are serious defects. If you encounter them, don’t buy them. In fact, the main purpose of buying a monitor is to watch the screen. The rest are very simple. , it is easy to repair. The main manufacturers of monitors are the following manufacturers: AUO, Huaying, Philips, Samsung, Hitachi, etc.