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1. Check whether the power supply and signal line are connected.
2. Check whether the test card recognizes the interface. The red flashing of the test card is not identified. Check whether the light board is in the same power source as the test card, or whether the light board interface is short-circuited to the ground and the interface cannot be identified. (Smart Test Card)
3. Check whether the 74HC245 is short-circuited by a short circuit or not, and whether the corresponding input/output pin of the 245 signal is pinned or short-circuited to other lines.
Note: Mainly check the power and enable (EN) signals.
B. Regular interlaced display overlaps during point sweep
1. Check if the A, B, C, D signal input ports are disconnected from 245 or they are short-circuited or welded.
2. Check whether the 245 corresponding A, B, C, D output terminals and 138 are disconnected or inadvertently welded or short-circuited.
3, detect A, B, C, D each signal is short-circuited or a signal and ground short circuit.
Note: The main test ABCD line signal.
C. One or several lines are not lit when all lights are on
1. Check if the line between 138 and 4953 is open or short circuited.
D. In line scanning, two or more lines (usually a multiple of 2, regular) light at the same time
1. Check if the A, B, C, D signals are short-circuited.
2. Check if the output of 4953 is shorted to other output terminals.
E. There is a single or multiple points (irregular) when the light is bright
1. Find out whether the corresponding control pin of this module measures a short circuit with this one.
2, replace the module or single lamp.
F. One or more columns are not lit when fully lit
1. Find the pin that controls this column on the module and check if it is connected to the driver IC (74HC595/TB62726,,,) output.
G. Single or single column highlighted, or entire row highlighted, and uncontrolled
1. Check if the column is shorted to the power ground.
2. Check if the line is shorted to the positive side of the power supply.
3, replace its driver IC.
H. The display is confusing, but the signal output to the next board is normal
1. Detect whether the corresponding STB latch output of the 245 and the latch of the driver IC are connected or the signal is shorted to other lines.
I. The display is confusing and the output is abnormal
1, detection clock CLK latch STB signal is short circuit.
2. Check whether the 245 clock CLK has input and output.
3. Check if the clock signal is shorted to other lines.
Note: The main detection clock and latch signal.
J. Show lack of color
1. Check whether the data of the color of 245 has input and output.
2. Detect if the data signal of this color is shorted to other lines.
3. Check whether the cascaded data port between the driver ICs of this color is open circuited or short circuited and soldered.
Note: The voltage detection method can be used to find the problem more easily, and whether the voltage of the data port is different from the normal one is determined and the fault area is determined.
K. There is a problem with the output
1. Check whether the output interface to the signal output IC is connected or short-circuited.
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 interface of the output interface or whether it is short-circuited.
4. Whether the output signals are short-circuited or shorted to ground.
5, check the output cable is good.
LED display unit board common faults and solutions
A. The whole board is not bright