LED display unit board failure and treatment methods

LED display unit board:

A. 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 on the test card flashes, it is not recognized. Check whether the light board and the test card have the same power ground, or if there is a short circuit between the signal and the ground at the light board interface, resulting in the inability to identify the interface. (Smart test card)

3. Check whether 74HC245 has any cold solder joints or short circuits, and whether the corresponding enable (EN) signal input and output pins on 245 are cold solder joints or short circuited to other circuits.

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

B. When scanning obliquely, the regular interlaced lines are not lit and the display screen overlaps

1. Check whether there is any broken wire, poor soldering or short circuit between the A, B, C, D signal input ports and 245.

2. Check whether the A, B, C, D output terminals corresponding to 245 and 138 are open circuit, poorly soldered or short circuited.

3. Check whether there is a short circuit between the A, B, C, and D signals or whether any signal is short-circuited to the ground.

Note: Mainly detect ABCD line signals.

C. One or more lines are not lit when all lines are lit

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

D. During line scanning, two or more lines (usually multiples of 2, regularly) light up at the same time

1. Check whether there is a short circuit between the A, B, C, and D signals.

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

E. When all lights are on, one or more spots (irregularly) are not lit

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

2. Replace the module or single lamp.

F. One or more columns are not lit when all columns are lit

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

G. There is a single point or column highlight, or an entire row highlight, and it is uncontrolled

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

2. Check whether the line is short-circuited to the positive pole of the power supply.

3. Replace its driver IC.

H. 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.

I. Display is confusing and 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 detect clock and latch signals.

J. Display color missing

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

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

3. Check whether the cascade data ports between the driver ICs of this color are open, short-circuited, or have poor soldering.

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.

K. 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 cascade output data port between the last driver IC is connected to the data port of the output interface or whether it is short-circuited.

4. Are there any output signals short-circuited to each other or to the ground?

5. Check whether the output cable is in good condition.