LCD splicing screen system common faults and analysis
Large-scale video surveillance system is a high-tech, complex system. Various kinds of fault phenomena may occur, but as long as the quality of the selected equipment and character is strictly related to the construction of strict standards and regulations, generally there will be no major problems. Even if they appear, as long as they calmly analyze and think, no Blindly dismantling and unloading can solve the problem better.
LCD splicing screen
1. Symptom: A black bar appears on the screen of the LCD splicing screen, and it may scroll up or down slowly.
Failure Analysis: This phenomenon may be caused by the power supply itself or the problem of the ground loop.
Solution: On the control panel, only one camera output signal with no power problem is connected nearby. If the above interference phenomenon does not appear on the monitor, the control panel just shows no problem. Next, a portable monitor can be connected nearby to the video output of the front camera and each camera can be checked one by one. If yes, proceed with the processing. If not, the interference is caused by ground loops and other causes.
2, the phenomenon of failure: LCD splicing screen appears wood grain interference.
Failure analysis: The appearance of wood grain interference does not drown the normal image when it is light, and the image cannot be viewed (or even destroy the synchronization) when it is serious. This cause of Shouyang phenomenon is more complicated. There are roughly the following reasons.
Cause one: The quality of the video transmission line is not good, especially the shielding performance is poor (the screening network is not a good quality copper network, or the shielding network is too sparse to achieve a shielding effect); the line resistance of the video line is too large, causing a signal Large attenuation occurs; the characteristic impedance of the video line is not 75 ohms.
Solution: After using the elimination method to eliminate other possibilities one by one, it can finally be considered from the perspective of bad video lines. If it is a cable quality problem, the best way is of course to replace all the cables and replace them with the ones that meet the requirements.
Cause two: The power supply system is not "clean". The fact that the power supply is not "clean" means that an interference signal is superimposed on a normal power supply (50 Hz power frequency). Most of the interference signals on the power supply come from devices that use thyristors in the power grid. In particular, high-current, high-voltage thyristor devices have a very serious pollution to the power grid, which leads to the fact that the power supply in the same power grid is not “cleanâ€. Such as the power grid thyristor frequency modulation device, thyristor rectifier devices, thyristor AC-DC converter devices, etc., will have pollution on the power supply.
Solution: The entire system can be solved by using clean power or online UPS power supply.
Cause 3: There is a strong source of interference near the system.
Solution: Judgment through investigation and analysis. Strengthen the shielding of the camera, as well as measures such as grounding the pipeline of the video cable.
3, the phenomenon of failure: LCD splicing screen produces a deeper and more chaotic large area moire interference, as well as all the image destruction, the shape of the image and synchronization signals.
Fault analysis: The fault caused by the short circuit and open circuit of the video cable's core wire and shielding network. Mostly appear on BNC connectors or other types of video connectors. That is, when this kind of fault phenomenon occurs, it is not always the signal of the entire system that causes problems, but only appears in the number of poorly-connected paths.
Solution: Seriously inspect the BNC connector one by one, remanufacture the problematic BNC connector, and reinstall it with the correct welding method.
4. Symptoms: The screen on the LCD splicing screen produces several lines with the same scale and vertical stripes.
Failure analysis: failure due to mismatch of the characteristic impedance of the transmission line. Because the characteristic impedance of the video transmission line is not 75 ohms, which results in impedance mismatch and loss of balance, the characteristic impedance and distribution parameters of the video cable do not meet the requirements.
Solution: Use "start series resistor" or "terminal parallel resistor" method. In addition, when the video transmission distance is short (typically within 150m), the above-mentioned interference phenomenon may not necessarily occur using the above video cable with impedance mismatch and distribution parameters that are too large. The fundamental method to solve the above problems is to ensure the quality when purchasing video cables. When necessary, carry out sampling inspection on the cable.
5, the phenomenon of failure: the screen on the LCD splicing screen produces a number of fine fringe interference.
Failure analysis: Mostly because there is a strong, high-frequency space radiation source near the central control room of the transmission system and the system front-end.
Solution: When surveying the system site, it is necessary to investigate the surrounding environment in detail and try to avoid or stay away from the radiation source. If the radiation source cannot be avoided, the front end and the center equipment are shielded, and the transmission line and the pipeline are piped and grounded.
6, the phenomenon of failure: no image display on the LCD splicing screen.
Failure analysis: Check one by one, if the check is due to the monitor host and other equipment and its connection caused no image display.
Solution: The microcomputer switches the output of the host computer to the coaxial cable connector on the LCD splicing screen to cause a short circuit or open circuit; the corresponding output terminal of the computer switching host computer is damaged; the TV set for dual purpose monitoring is displayed in the TV status, or the LCD splicing screen is broken; With a VCR, you need to power on the VCR and adjust it to the TV accordingly.
7, the phenomenon of failure: fiber transmission mode caused no LCD display splicing screen.
Fault analysis and solution: First, check whether the connection between the electric, optical cable, optical transmitter and receiver is correct, and check whether the supply voltage and current meet the requirements; the output carrier of the optical transmitter does not have a video input signal. Check the video input process on the optical transmitter: disconnect the video signal from the transmitter, and use the video coaxial cable to input the video signal directly to the LCD panel. If there are images, it indicates that there is a problem with the optical transmitter. Replace it. Can; light receiver problems. Such as light transmitter, LCD splicing screen and connection no problem, but still a black screen, just replaced the light receiving terminal; LCD splicing screen problem. If there is no problem in the light receiving and transmitting terminal and the connection with the monitor is correct, but the screen is still black, replace the screen of the LCD splicing screen.
8, the phenomenon of failure: the monitor image appears more uniform snowflake interference, poor image quality.
Failure analysis and solution: The main reason for this phenomenon can be analyzed from the following two aspects: 1 Optical fiber transmission: optical receiver problems. First, the optical power meter is used to check the optical power entering the optical receiving terminal. If the optical power meets the requirements, the optical receiving terminal needs to be replaced; the optical transmitting terminal has a problem. If the check enters when the optical power of the receiver is lower than the calibration value, then the optical power meter and an optical fiber jumper are used to check the optical output of the optical transmitter; if the optical output is low, the optical transmitter needs to be replaced; Optical connector problem. If checking the light output of the light emitting end meets the requirements, it is a problem of the optical connector. Wipe the optical connector clean or replace it with a good quality; the transmission distance is too far and the optical fiber loss is too large, and an optical amplifier needs to be added. 2 Coaxial cable transmission mode: The illumination intensity of the monitoring point is too low, making the video transmission line bad, making the amplitude of the video signal smaller; the camera sensitivity is low or the lens aperture is too small; the quality of the LCD monitor itself; the video transmission line is not good , Make the video signal to reduce too much, resulting in smaller video signal amplitude; video transmission lines, video amplifiers and other video equipment quality is not good; video cable plugs, sockets and other bad welding. Good quality video equipment and video transmission lines can be used to ensure that the amplitude of the video signal meets the specification standards.
9 Symptom: There is a mosaic phenomenon when playing back images and video files.
Failure analysis: 1 As the host signal is not good, the network is not good, resulting in loss of some video and audio signals; 2 during the period of the client to generate a mosaic video, whether there are other reasons leading to severe shortage of resources. For example, while the client is previewing the data transmitted from the host, it is performing a multi-channel playback operation that exceeds the system capability, thereby consuming the CPU resources. Because the host resource is exhausted, the video data cannot be written to the hard disk, resulting in mosaics.
Solution: The former can be used to improve the transmission channel environment and expand the transmission channel bandwidth. In the latter case, the client's configuration must be improved to increase its CPU and memory capacity.
10, failure phenomenon: the image has animated sense.
Failure analysis: 1 server host corresponding channel recording settings, the frame rate is adjusted too low; 2 network communication bandwidth is not enough, then should be appropriate to reduce the host side of the video quality; 3 due to the server host this channel is set to LAN transmission The mode is in the same local area as the first-level client and the extended client. Therefore, the extended client may not be previewed properly at this time.
Solution: Put the system recovery disk with the random drive into the floppy disk drive to restart the system. At this time, the system will automatically recover, that is, return to the factory settings. After the system recovery is complete, remove the floppy disk and restart the machine. When the system starts up, it is reset according to its own needs.
11, the phenomenon of failure: the image screen has a sense of jitter.
Failure Analysis: The display refresh rate is set too low.
Solution: Enter the “Display Properties†and click “Settingsâ€, select “Advanced†and select “LCD Monitor†to adjust the new frequency to 75Hz. After confirming the exit, you can solve this problem.
LCD splicing screen
1. Symptom: A black bar appears on the screen of the LCD splicing screen, and it may scroll up or down slowly.
Failure Analysis: This phenomenon may be caused by the power supply itself or the problem of the ground loop.
Solution: On the control panel, only one camera output signal with no power problem is connected nearby. If the above interference phenomenon does not appear on the monitor, the control panel just shows no problem. Next, a portable monitor can be connected nearby to the video output of the front camera and each camera can be checked one by one. If yes, proceed with the processing. If not, the interference is caused by ground loops and other causes.
2, the phenomenon of failure: LCD splicing screen appears wood grain interference.
Failure analysis: The appearance of wood grain interference does not drown the normal image when it is light, and the image cannot be viewed (or even destroy the synchronization) when it is serious. This cause of Shouyang phenomenon is more complicated. There are roughly the following reasons.
Cause one: The quality of the video transmission line is not good, especially the shielding performance is poor (the screening network is not a good quality copper network, or the shielding network is too sparse to achieve a shielding effect); the line resistance of the video line is too large, causing a signal Large attenuation occurs; the characteristic impedance of the video line is not 75 ohms.
Solution: After using the elimination method to eliminate other possibilities one by one, it can finally be considered from the perspective of bad video lines. If it is a cable quality problem, the best way is of course to replace all the cables and replace them with the ones that meet the requirements.
Cause two: The power supply system is not "clean". The fact that the power supply is not "clean" means that an interference signal is superimposed on a normal power supply (50 Hz power frequency). Most of the interference signals on the power supply come from devices that use thyristors in the power grid. In particular, high-current, high-voltage thyristor devices have a very serious pollution to the power grid, which leads to the fact that the power supply in the same power grid is not “cleanâ€. Such as the power grid thyristor frequency modulation device, thyristor rectifier devices, thyristor AC-DC converter devices, etc., will have pollution on the power supply.
Solution: The entire system can be solved by using clean power or online UPS power supply.
Cause 3: There is a strong source of interference near the system.
Solution: Judgment through investigation and analysis. Strengthen the shielding of the camera, as well as measures such as grounding the pipeline of the video cable.
3, the phenomenon of failure: LCD splicing screen produces a deeper and more chaotic large area moire interference, as well as all the image destruction, the shape of the image and synchronization signals.
Fault analysis: The fault caused by the short circuit and open circuit of the video cable's core wire and shielding network. Mostly appear on BNC connectors or other types of video connectors. That is, when this kind of fault phenomenon occurs, it is not always the signal of the entire system that causes problems, but only appears in the number of poorly-connected paths.
Solution: Seriously inspect the BNC connector one by one, remanufacture the problematic BNC connector, and reinstall it with the correct welding method.
4. Symptoms: The screen on the LCD splicing screen produces several lines with the same scale and vertical stripes.
Failure analysis: failure due to mismatch of the characteristic impedance of the transmission line. Because the characteristic impedance of the video transmission line is not 75 ohms, which results in impedance mismatch and loss of balance, the characteristic impedance and distribution parameters of the video cable do not meet the requirements.
Solution: Use "start series resistor" or "terminal parallel resistor" method. In addition, when the video transmission distance is short (typically within 150m), the above-mentioned interference phenomenon may not necessarily occur using the above video cable with impedance mismatch and distribution parameters that are too large. The fundamental method to solve the above problems is to ensure the quality when purchasing video cables. When necessary, carry out sampling inspection on the cable.
5, the phenomenon of failure: the screen on the LCD splicing screen produces a number of fine fringe interference.
Failure analysis: Mostly because there is a strong, high-frequency space radiation source near the central control room of the transmission system and the system front-end.
Solution: When surveying the system site, it is necessary to investigate the surrounding environment in detail and try to avoid or stay away from the radiation source. If the radiation source cannot be avoided, the front end and the center equipment are shielded, and the transmission line and the pipeline are piped and grounded.
6, the phenomenon of failure: no image display on the LCD splicing screen.
Failure analysis: Check one by one, if the check is due to the monitor host and other equipment and its connection caused no image display.
Solution: The microcomputer switches the output of the host computer to the coaxial cable connector on the LCD splicing screen to cause a short circuit or open circuit; the corresponding output terminal of the computer switching host computer is damaged; the TV set for dual purpose monitoring is displayed in the TV status, or the LCD splicing screen is broken; With a VCR, you need to power on the VCR and adjust it to the TV accordingly.
7, the phenomenon of failure: fiber transmission mode caused no LCD display splicing screen.
Fault analysis and solution: First, check whether the connection between the electric, optical cable, optical transmitter and receiver is correct, and check whether the supply voltage and current meet the requirements; the output carrier of the optical transmitter does not have a video input signal. Check the video input process on the optical transmitter: disconnect the video signal from the transmitter, and use the video coaxial cable to input the video signal directly to the LCD panel. If there are images, it indicates that there is a problem with the optical transmitter. Replace it. Can; light receiver problems. Such as light transmitter, LCD splicing screen and connection no problem, but still a black screen, just replaced the light receiving terminal; LCD splicing screen problem. If there is no problem in the light receiving and transmitting terminal and the connection with the monitor is correct, but the screen is still black, replace the screen of the LCD splicing screen.
8, the phenomenon of failure: the monitor image appears more uniform snowflake interference, poor image quality.
Failure analysis and solution: The main reason for this phenomenon can be analyzed from the following two aspects: 1 Optical fiber transmission: optical receiver problems. First, the optical power meter is used to check the optical power entering the optical receiving terminal. If the optical power meets the requirements, the optical receiving terminal needs to be replaced; the optical transmitting terminal has a problem. If the check enters when the optical power of the receiver is lower than the calibration value, then the optical power meter and an optical fiber jumper are used to check the optical output of the optical transmitter; if the optical output is low, the optical transmitter needs to be replaced; Optical connector problem. If checking the light output of the light emitting end meets the requirements, it is a problem of the optical connector. Wipe the optical connector clean or replace it with a good quality; the transmission distance is too far and the optical fiber loss is too large, and an optical amplifier needs to be added. 2 Coaxial cable transmission mode: The illumination intensity of the monitoring point is too low, making the video transmission line bad, making the amplitude of the video signal smaller; the camera sensitivity is low or the lens aperture is too small; the quality of the LCD monitor itself; the video transmission line is not good , Make the video signal to reduce too much, resulting in smaller video signal amplitude; video transmission lines, video amplifiers and other video equipment quality is not good; video cable plugs, sockets and other bad welding. Good quality video equipment and video transmission lines can be used to ensure that the amplitude of the video signal meets the specification standards.
9 Symptom: There is a mosaic phenomenon when playing back images and video files.
Failure analysis: 1 As the host signal is not good, the network is not good, resulting in loss of some video and audio signals; 2 during the period of the client to generate a mosaic video, whether there are other reasons leading to severe shortage of resources. For example, while the client is previewing the data transmitted from the host, it is performing a multi-channel playback operation that exceeds the system capability, thereby consuming the CPU resources. Because the host resource is exhausted, the video data cannot be written to the hard disk, resulting in mosaics.
Solution: The former can be used to improve the transmission channel environment and expand the transmission channel bandwidth. In the latter case, the client's configuration must be improved to increase its CPU and memory capacity.
10, failure phenomenon: the image has animated sense.
Failure analysis: 1 server host corresponding channel recording settings, the frame rate is adjusted too low; 2 network communication bandwidth is not enough, then should be appropriate to reduce the host side of the video quality; 3 due to the server host this channel is set to LAN transmission The mode is in the same local area as the first-level client and the extended client. Therefore, the extended client may not be previewed properly at this time.
Solution: Put the system recovery disk with the random drive into the floppy disk drive to restart the system. At this time, the system will automatically recover, that is, return to the factory settings. After the system recovery is complete, remove the floppy disk and restart the machine. When the system starts up, it is reset according to its own needs.
11, the phenomenon of failure: the image screen has a sense of jitter.
Failure Analysis: The display refresh rate is set too low.
Solution: Enter the “Display Properties†and click “Settingsâ€, select “Advanced†and select “LCD Monitor†to adjust the new frequency to 75Hz. After confirming the exit, you can solve this problem.
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