Common Faults and Solutions for LED Display Panel Unit Board

The whole board is not lit

1. Check whether the power supply and signal line are connected.

2. Check whether the test card can identify the interface. If the red light of the test card flashes, it is not recognized. Check whether the light board and the test card are on the same power ground, or the light board interface has a short circuit between the signal and the ground, which makes the interface unrecognizable. (Intelligent test card)

3. Check whether the 74HC245 has a short circuit, and whether the corresponding enable (EN) signal input and output pins on 245 are short-circuited or short-circuited to other lines.

Note: Mainly check the power supply and enable (EN) signal.

During the point-slant scanning, the regular interlaced lines are not lit and the display screen overlaps

1. Check whether there is a disconnection or a disconnection or a short circuit between the A, B, C, D signal input port and 245.

2. Check whether the A, B, C, D output terminals corresponding to 245 and 138 are disconnected or disconnected or short-circuited.

3. Check whether the A, B, C, D signals are short-circuited or a signal is short-circuited to the ground.

Note: Mainly check the ABCD line signals.

When all lights are on, one or several rows are not lit.

1. Check whether the line between 138 and 4953 is open, poorly soldered or short-circuited.

When scanning rows, two or several rows (usually multiples of 2, with regularity) are lit at the same time.

1. Check whether the A, B, C, and D signals are short-circuited.

2. Check whether the output terminal of 4953 is short-circuited with other output terminals.

When all lights are on, there is a single point or multiple points (irregular) that are not lit.

1. Find the control pin corresponding to the module to measure whether it is short-circuited with the row.

2. Replace the module or single lamp.

When all lights are on, one or several columns are not lit.

1. Find the pin that controls the column on the module and test whether it is connected to the output terminal of the driver IC (74HC595/TB62726,,,).

There is a single point or a single column that is highlighted, or the entire row is highlighted and is not controlled.

1. Check whether the column is short-circuited with the power ground.

2. Check whether the row is short-circuited with the positive pole of the power supply.

3. Replace its driver IC.

The display is chaotic, but the signal output to the next board is normal.

1. Check whether the STB latch output terminal corresponding to 245 is connected to the latch terminal of the driver IC or the signal is short-circuited to other lines.

The display is chaotic and the output is abnormal .

1. Check whether the clock CLK latch STB signal is short-circuited.

2. Check whether the clock CLK of 245 has input and output.

3. Check whether the clock signal is short-circuited to other lines.

Note: Mainly check the clock and latch signals.

Display is missing color .

1. Check whether the data terminal of the color of 245 has input and output.

2. Check whether the data signal of the color is short-circuited to other lines.

3. Check whether the cascaded data port between the driver ICs of the color is open or short-circuited, or has a cold solder joint.

Note: The voltage detection method can be used to find the problem more easily. Check whether the voltage of the data port is different from the normal one and determine the fault area.

There is a problem with the output .

1. Check whether the line from the output interface to the signal output IC is connected or short-circuited.

2. Check whether the clock latch signal of the output port is normal.

3. Check whether the cascaded output data port between the last driver IC is connected to the data port of the output interface or short-circuited.

4. Check if the output signals are short-circuited to each other or to the ground.

5. Check if the output wiring is in good condition.