How to repair LED screen? What can we do to position the problems, and figure them out with high efficiency and simple operation?
This articles will list the methods that help you to deal with technical problems you may face in using LED display screen including short circuit, failure of LED display module and the whole LED display screen. Finally, we will dicuss the steps for you to debug other problems.
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Short Circuit
Failure of LED Display Module
Failure of LED Screen
Troubleshooting Steps
Xingwei Video Tutorial for LED Screen Repair
1.Short Circuit
(1)Resistance detecting: use multimeter to examine the range of resistance. Detect the resistance value of a certain point of a normal circuit board, then detect that value of other circuit board to find out whether the resistance value is different from the normal value. If the value is not within a reasonable range, meaning the problem comes from here.
(2)Voltage detection: use multimeter to detect the ground voltage of a certain point of the circuit which is suspected of having problems. Comparing the detected value with normal one to find out whether there is trouble.
(3)Short circuit detection: turn on the functions of multimeter to find out whether there is short circuit. This must be done when the screen powering off to avoid damage ammeter.
If there is problem of short circuit, deal with it first to prevent from burning out other components.
(4)Voltage drop detection: use diode drop function to detect voltage drop of different pins. Basically, the voltage drop value of pins that locate on the same type of integrated circuit should be the same.
This detection should be run when shutting off the screen to avoid unnecessary damages. However, this method has its limitation. For instance, if the components have high impedance, the differences will not be examined.
2.Failure of LED Display Module
(1)Non displaying on part of the module such as rows missing and lines missing
a.Check whether the flat cable connects well with the power line of the first abnormal LED module in the direction of signal input.
b.check whether the signal input is normal. If there is confusing color, then check the signal contact of the first abnormal LED module in the direction of signal input.
You can examine it by plugging in and out multiple times. If there is a problem, you can choose to replace the flat cable.
c.Check whether the power pins of 74HC138 decoding chip and 4953 line management chip are poor welding or suffering short circuit. If yes, repair them or change new chips.
Part of the LED module Displaying Missing Such as Rows Missing and Lines Missing
(2)No displaying on a single LED module a.Check whether the power supply contact is normal. For instance, whether the power plug is loose or not.
b.If there is wrong color displaying or color inconsistency but correct pictures, the problem may occur in signal input. Plug out the cable then plug in again, or replace the flat cable.
If the problem still exists after replacing the flat cable, check whether the interface of the PCB board is working properly.
(3)Single Pixel Dark
Use the X1 resistance function of the multimeter to detect whether the LED lamp bead work normally or not.
Connect the positive electrode of LEDs with the balck probe and the negative electrode with the red probe. If the LED lamp bead is on, means it still works. If the light bead doesn’t light on, means it is bad. Then you have to replace it.
(4)Dead pixel maintenance
According to specific condition, choose the right maintenance method:
a.Front maintenance:
Use proper screwdriver to remove the screws for fixing mask and remove the mask to replace the LED lamp light.
After the replacement and sealing finishing, install the mask again, and tighten the screw (please be careful to avoid taking pressure on LEDs) and clean the residual glue on the surface.
b.Back maintenance
Plug out the signal cable, and use a screwdriver to remove the screws on the back side. For safety, please notice that do not unplug the power cable.
Take the LED screen module out carefully, move it to the back side of the LED cabinet, and then replace the LED lamp light in the same way of replacing it as front maintenance.
(5)How to replace LED lamp bead?
Remove the gel around the LEDs with sharp tools such as a tweezer until the pins are clearly exposed.
Use a tweezer to keep the lamp bead in place, and solder it with soldering iron at temperature around 40°C (too high temperature will damage the LED display) for less than 3 seconds.
Install the right light beads on the PCB board (the long probe of LED lamp bead is the positive electrode, and the short one is the negative electrode. And the square hole on PCB board is for the positive electrode while the round hole is for the negative electrode).
Melt down a little solder wire and touch it with the solder tip, then solder the LEDs and PCB board with the solder wire. Finally, seal the LED display with the same type of gel (PH=7).
(6)Color missing on LED module
a.Check the signal cable connection and reconnect, also check the power supply for the first module in the row.
b.Check whether the flat cable is working normal. If any problem, reconnect the cable.
c.Change a LED display module to see whether the color missing phenomenon disappears.
(7)One row of LED display module displaying color inconsistency
This problem may be caused by the failure of the pins of the driver IC that controls this row.
First, position the corresponding driver IC. You can find it through the circuit diagram, and replace it and drive it.
(8)How to replace driver IC?
First, test the IC card. Second, remove the defect IC. Third, add solder. Fourth, get rid of excess solder. Fifth, test it.
3.Failure and Solutions of LED Display Screen
(1)No displaying on the entire LED display (all black)
a.Check whether the LED display screen has already been powered on. Turn on the swift of power distributor, the power indicator should be on.
b.Check the signal cable, reconnect it until the green indicator twinkling as normal.
c.Examine whether the connection between LED sending card and LED receiving card is normal.
If the sending card is not working normal, for example, the green indicator is off or keeps lighting, it means there is no signal, then check it to find out problems or replace it.
What is more, you can check the input voltage DC5V of the receiving card, especially for the first LED receiver card.
d.If the PC has not been turned on, start up it and open the LED studio software.
e.Check the DVI cable. You can power off the computer then reconnect the DVI cable.
f.Find out whether is mistake in the setting of DVI card. According to the right steps of controlling system operation, setting up the LED studio software and reconnect the signal cable.
g.Check the HUB to judge whether it is working normally.
(2)Garbled displaying on the LED display
a.Check out whether the connection of receiving card and sending card is normal.
If the sending card is not working normal, for example, the green indicator is off or keeps lighting, it means there is no signal, then check it to find out problems or replace it.
b.Ensure the internet cable is appropriate and will not influence the displaying performances due to bad quality and inappropriate parameters.
c.Check whether the LED studio setting has mistake or not. If there is any problem, setting up the LED studio software and reconnect the signal cable based on the controlling system operation steps.
d.Check the connection of signal cable to ensure it performs well.
Garbled Displaying and Disordered Picture of LED Display Screen
(3)Each display unit performs the same content
This may be caused by the lack of cascading files. Send the cascading file again, and plug the internet cable of computer into the output port near the indicator lamp of LED sending card.
(4)The brightness of LED display screen is low, and pictures are fuzzy
The reason can be the wrong setting of sending card and functional card. Please restore the default setting and store the setting, and control the minimum brightness values larger than 80.
(5)Disordered or overlapped displaying on the entire LED display
a.Check connection between cabinets and signal cable. Replug the cable or replace it.
b.Check the DVI cable which connects the multi-media card and sending card. If there is problem, reinforce the connection.
c.Check whether the LED studio setting has mistake or not. If there is any problem, setting up the LED studio software and reconnect the signal cable based on the controlling system operation steps.
d.Check the working conditions of LED sending card. If they do not work properly, choose to repair or replace them.
(6)Winkling/Shaking displaying on the entire LED display
a.Check whether the sending card and receiving card is working normal. If the green indicator is off or keeps lightning it means there is no signal.
b.Ground wire break off. Check out whether there is a problem of connection between the ground wire and the LED screen display.
c.Check the connection between cabinets and signal cable. Replug the cable or replace it.
d.Check whether the LED studio setting has mistake or not. If there is any problem, setting up the LED studio software and reconnect the signal cable based on the controlling system operation steps.
e.Check the DVI cable which connects the multi-media card and sending card. If there is problem, reinforce the connection.
(7)No displaying on parts of the entire LED display
a.Check whether the sending card and receiving card are working normal. If the green indicator is off or keeps lightning it means there is no signal.
b.Check whether the LED studio setting has mistake or not. If there is any problem, setting up the LED studio software and reconnect the signal cable based on the controlling system operation steps.
Not Displaying Synchronously with Computer and No Displaying on Part of the Screen
(8)Not displaying synchronously with the computer
Check the DVI card setting, and the multiple display mode should be “duplicateâ€.
(9)No displaying on several modules
a.If there is no displaying on a single row, it may represent the signal input has some problems. Check it, replug it and also check the power connection for the first module in the row.
b.If there is no displaying on one corner of the cabinet, check if the related power supply is working normal or not.
(10)When starting the LED screen, there is a caution that LED screen system is not found.
a.Check the connection between serial port line, USB and sending card. Reassure the connections, if they are loosen, reconnect them.
b.The COM or USB port is broken. Replace the control computer and serial port line.
c.The LED sending card is broken. Replace the sending card.
d.No installation of USB driver. Install the related latest software or install the USB driver.
(11)Garbled displaying on the LED display only few seconds when powering on the screen
This is a normal phenomenon that represents the LED display board is ready to work. This garbled displaying will disappear basically within two seconds and the screen will run normally then.
(12)Communication failure or loading failure
a.Ensure the LED control system devices have already been powered on.
b.Make sure the connection of serial port line is not loosen or has problems itself.
c.Make sure we have chosen the right control software and control card. And ensure we choose the right data transmission method, serial port, data transfer rate and correct setting of LED control software.
d.Check the jumper cap to see whether is loose or comes off. If the answer for both is no, then make sure the direction of the jumper cap is correct.
e.If the problem is not caused by the reasons listed before, use a multimeter to detect whether the serial ports of the control computer and LED control system devices work normally. If yes, you can send them to corresponding manufactures for repair and maintenance.
4.Troubleshooting Steps of LED Control System
First, check the setting of the graphic processing unit according to guidance.
Second, check the connection of cables such as DVI cable, internet cable, the connection of host control card and PCI port and so on.
Third, check the power supply of both the control computer and LED display screen. When there is inadquate power supply for LED display cabinet, the screen will flicker when the screen displaying the whole white picture.
Choose the right power supply based on the requirement of the cabinet.
Fourth, check whether the green indicator of the LED sending card is flashing regularly. If it is flashing, then turn to step 6.
If it does not flash, restart it, and check whether the green light is flashing regularly before entering the win98/2k/XP system. If flashing, go to step 2.
Please check whether the DVI cable is connected properly. If the problem is not solved because sending card, graphics card, and DV cable, please replace it separately and repeat step 3.
Fifth, setting upon the software instruments or reinstall it, and then reset it until the green indicator is flashing. Otherwise, repeat the third step.
Sixth, check whether the green indicator (data light) of the receiving card flashes synchronously with the green indicator of the sending card. If iyes, go to step 8, and check whether the red light of the power supply is still on.
If it is on, go to step 7. If it does not, check the yellow light of the power supply. If it is not on, check whether the power supply is connected reversely or there is no power output. If it is on, check whether the power supply voltage is 5V.
If the green indicator is off, remove the adapter and the cable and try again.
If the problem is not solved, meaning the LED receiving card has some problem. Replace the LED receiving card, and then repeat step 6.
Seventh, check whether the internet cable is well connected or the length of it is too long. Please be noticed that the length should be within 100 meters without a repeater. If the answer is yes, then cope with it.
However, if the problems are not solved after the repairment, then the trouble may happen in the LED receiving card. Replace the receiving card and repeat step 6.
Eighth, check out whether the power lamp is on. If not, turn to step 7, and check if the port of the defined line is compatible with the unit board.
5.The Bottom Line
This article introduces practicle guidance for how to repair LED screen from aspects of LED display module, short circuit and the whole screen (whether for indoor LED display screen or outdoor LED display). And give detailed steps for you to shoot the trouble and deal with it. For more information, welcome turn to our LED FAQ page!