LCD monitor common fault analysis and solution
Generator Container,Power Container,Iso Generator Container,Prefab Gas Container Yangzhou Tonglee Reefer Container Co., Ltd. , https://www.cimctlc.com
When using the LCD monitor to observe the image, why does the image distortion, distortion, line and field synchronization, or even failure of the input signal occur?
First, the industry standard for LCD monitors specifies that professional LCD monitors have an input signal amplitude of 1Vp-P±3dB (approximately 0.7Vp-P-1.4Vp-p) and an input impedance of 75 ohms. Therefore, if the input signal is not standardized due to cable attenuation, impedance mismatch, or the BNC head of the transmission cable, the input signal amplitude is much lower than 0.7 pp; either the camera output is not regulated or some irregularity is connected. When the input signal (such as distributor, amplifier, etc.) causes the input signal amplitude to be much larger than 1.4Vp-p, it may cause image distortion, line and field synchronization, etc.
Second, due to the wide range of video frequency, video signals are more susceptible to interference during transmission (including 50Hz power interference, electromagnetic interference, etc.), thus affecting image quality. Severe disturbances may cause images to be distorted, deformed, raceways, and lines and fields to be out of sync. Therefore, during the installation of the monitoring system, the video line must be far away from sources of electromagnetic interference.
Third, the potential difference between the front-end device, the control host device, and the terminal device may also interfere with the video signal, resulting in distortion of the image signal or image appearance of a race track if the entire system is powered on (ie, the front-end device, the master When the control equipment and terminal equipment are connected to the BNC head to connect the front and rear equipment when they are powered on, it may be caused by the potential difference between the ground wire of the front and rear equipment (actually the shielding layer of the transmission cable). Jumping over fire, this flashover will destroy the component at the input or the leveling line in the casserole of the PCB board. Causes the input to open circuit and input no image fault. Therefore, the construction of monitoring system engineering should be designed and constructed in strict accordance with the specifications. The grounding bus should use copper conductors with sufficient cross-sectional area to ensure ground-to-ground resistance at the front and rear ends.
If the LCD monitor appears black screen, the first consideration is the power circuit is not good caused by: performance as a panel button without any reaction, the indicator light is not bright, first check the 12V voltage is good or not, follow the check 5V voltage is good, because A / D drive The operating voltage of the chip signal processing part of the chip is 5V, so when the fault can not be found by the machine, use a multimeter to measure 5V voltage first, if there is no 5V voltage or 5V voltage becomes very low, then one may be the power circuit There was a problem with the input stage, which means that there was a problem with the 12V to 5V power supply.