Bad points are the most common problems that LED screens are prone to, which refer to the inability of LED screens to function properly and the appearance of black spots. Other common problems include overall screen failure, partial screen failure, overall screen flicker, partial flicker, and screen flicker. This article briefly introduces the corresponding common troubleshooting methods for LED screens to address some common problems:
Interface issue: Computer information cannot be displayed, check cable
Power supply issue: The LED display uses a low-voltage high current power supply, which is not significantly different from a regular DC power supply
Driver issue: If each row or column is not displayed, it is the corresponding driver circuit (chip) issue. Replace it
Display issue: Long term use of LED display screens can cause damage and aging. Repair and replacement are sufficient.
1. Output issues
1. Check if the circuit from the output interface to the signal output IC is connected or shorted.
2. Check if the clock latch signal of the output port is normal.
3. Check whether the cascade output data port between the last driver IC is connected to the data port of the output interface or if there is a short circuit.
4. Is there a mutual short circuit or a short circuit to ground in the output signals.
5. Check if the output cable is in good condition.
2. One or several lines that are fully lit are not lit
1. Check for open circuit, faulty soldering, or short circuit in the circuit between 138 and 4953.
3. The entire board does not light up
1. Check if the power supply and signal lines are connected.
2. Check if the test card identifies the interface. If the red light on the test card flashes, there is no identification. Check if the light board is connected to the same power source and ground as the test card, or if there is a signal short circuit between the light board interface and ground, resulting in the inability to identify the interface. (Smart Test Card)
3. Detect whether there is a faulty soldering or short circuit on 74HC245, and whether the corresponding enable (EN) signal input and output pins on 245 are faulty soldering or short circuited to other lines.
Note: Mainly check the power supply and enable (EN) signal.
4. During oblique scanning, the regular interlacing does not light up, and the display screen overlaps
1. Check for any broken wires, solder joints, or short circuits between the A, B, C, and D signal input ports and 245.
2. Check if there is an open circuit, faulty soldering, or short circuit between the A, B, C, and D output terminals corresponding to 245 and 138.
3. Detect if there is a short circuit between signals A, B, C, and D, or if a certain signal is short circuited to ground.
Note: Mainly detects ABCD line signals.
5. The display is chaotic, and the signal output to the next board is normal
1. Detect if the STB latch output terminal corresponding to 245 is connected to the latch terminal of the driver IC or if the signal is shorted to another circuit.
6. When all lights are on, one or several columns do not light up
1. Find the pin on the module that controls this column and test if it is connected to the output terminal of the driver IC (74HC595/TB62726,,).
7. Uncontrolled single point or single column highlighting, or whole row highlighting
1. Check if the column is short circuited to power or ground.
2. Check if the line is short circuited to the positive pole of the power supply.
3. Replace its driver IC.
8. Display confusion and abnormal output
1. Check if the clock CLK latch STB signal is short circuited.
2. Check if the clock CLK of 245 has input and output.
3. Detect if the clock signal is shorted to another circuit.
Note: Mainly detects clock and latch signals.
9. Display missing color
1. Check if there are inputs and outputs on the data end of the color 245.
2. Detect if the data signal of this color is shorted to another line.
3. Check if there is an open circuit, short circuit, or faulty soldering in the cascade data port between the driver ICs of this color.
Note: Voltage detection method can be used to easily identify problems, detect whether the voltage of the data port is different from normal, and determine the fault area.
10. Display screen shaking with horizontal bars
Check if the common ground wire connecting the computer is loose or if the communication cable is loose. If the operator cannot determine the cause of the problem or is not very familiar with the computer, do not easily open the chassis. You can contact the LED display screen manufacturer before handling it.