What Is an LCD Monitor?
The liquid crystal display is an active matrix liquid crystal display driven by a thin film transistor (TFT). It mainly uses a current to stimulate the liquid crystal molecules to generate dots, lines, and surfaces in cooperation with a back light tube to form a picture. IPS, TFT, and SLCD are all subclasses of LCD. [1]
- LCD is a display using liquid crystal as a material.
LCD monitor white screen
- The white screen is caused by the normal backlight and the screen does not correctly receive the signal from the motherboard.
- White screen
LCD monitor black screen
- In the actual maintenance process, the black screen is the most common situation, and the black screen is divided into three types: power light flashing, long light or off. [8]
- (1) The power supply of the LCD display flashes. The flashing of the power supply is mostly due to the short-circuit of the high-voltage board's back-stage switch. When the LCD driver board sends out the control voltage to turn on the high-voltage board, the booster circuit starts to work, but one or a The short circuit to the ground of the switch tube pulls down the main power supply, which causes the power supply of the LCD driver board to be lowered. When the power supply of the LCD panel is abnormal, the turn-on signal to the high-voltage board is cancelled, and the voltage output of the power supply board returns to normal. Therefore, the power light turns on and off repeatedly, and the failure of replacing the corresponding faulty component should be resolved. [8]
- (2) The power light of the LCD display is always on. The power light is on to determine that the power supply is normal, mainly due to the high heat generated by the final stage or power supply components of the high-voltage inverter circuit, which is caused by long-term work. The fault is the booster coil, which is generally a problem of poor contact. The circuit should be checked. [8]
- (3) The power supply lamp of the LCD display is off. The power supply unit should not be checked. The power supply part should be checked. The 12V and 5V voltages should be checked. The 12V and 5V voltage should not be output. Poor performance, or base soldering, whether there is bulging of the capacitor, and the pulse width modulation of a single chip switching power supply, the pulse width modulation integrated controller generally used are SG6841, UC3842, UC3843 are also components with a higher failure rate. [8]
LCD backlight failure
- In addition to the above failure phenomena, LCD backlight failures are also common, mainly manifested in aging and complete damage, that is, no light. After the backlight ages, you can see that the image is yellow. Adjusting the color temperature and white balance can not be solved well. At the same time, the screen brightness is adjusted to the maximum and it is difficult to meet the requirements. This prompts you that it is time to change the lamp. [8]
- After the display with the single-tube structure is damaged, you can see the dim picture display when you turn on the screen and look at the screen in sunlight. The new multi-lamp display shows an uneven brightness when a certain lamp is damaged. For example, the upper part is dim, that is, the upper lamp is damaged. Touch the position of the display lamp with your hand. You can also judge whether the lamp is based on temperature comparison. Damaged, the temperature of the normal display lamp position should be consistent. However, most new-type displays have high-voltage balanced protection circuits, so when a lamp is damaged, the performance is often not uneven brightness, but the display cannot be turned on or the screen is blank after power-on, which depends on the specific display circuit. [8]