Common fault phenomenon of single module of unit board and detection and repair method

August 09, 2019

Common fault phenomenon of single module of unit board and detection and repair method

A. The entire module is not lit

1. Check if the power supply and signal cable are connected.
2. Detect whether the 74HC245 has a short circuit or not, and the corresponding enable (EN) signal input and output pin on the 74HC245 is soldered or short-circuited to other lines. Mainly check the power and enable (EN) signals.

B. In the oblique scan, the regular interlacing does not light up and the screen overlaps.

1. Check whether there is disconnection or cold welding or short circuit between the signal input port of interface A, B, C and D to 74HC245.
2. Detect whether there is open circuit or virtual welding or short circuit between the output terminals A, B, C and D corresponding to 74HC245.
3. Detect whether there is a short circuit between the signals of interface A, B, C, and D or a short circuit between a signal and ground.

C. One line or several lines are not lit when fully lit

1. Detect whether the line between 138 and 4953 is open circuit or virtual welding or short circuit.

D. When scanning a line, two or more lines are lit at the same time

1. Detect whether there is a short circuit between the signals of interface A, B, C, and D.
2. Detect if the output of the 4953 is shorted to other outputs.

E. Single or multiple points are not lit when fully illuminated

1. Find whether the control pin corresponding to the module is short-circuited with the line.
2. Replace the single lamp, disconnect the pin and the lamp.

F. One column or several columns are not lit when fully illuminated

1. Find the pin that controls the column on the module and measure whether it is connected to the output of the driver IC (TB62726).
G. Single or single column highlighting, or full line highlighting, and uncontrolled

1. Check if the column is shorted to the power ground.
2. Check if the line is shorted to the positive terminal of the power supply.
3. Replace the driver IC.

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

1. Check if the STB latch output end of the 74HC245 is connected to the latch terminal of the driver IC (TB62726) or the signal is shorted to other lines.

I. Display confusion, output is not normal

1. Detect whether the clock CLK latches the STB signal for short circuit.
2. Check if the clock CLK has input and output.
3. Check if the clock signal is shorted to other lines.

J. Display lack of color

1. Detect whether the driver IC has input and output corresponding to the data end of the color, and check whether the voltage of the data port is different from normal.
2. Check if the data signal of the color is short-circuited to other lines.
3. Check whether the cascaded data port between the driver ICs of this color has an open circuit or short circuit or a virtual solder.

K. Have a problem with the output

1. Check whether the line 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 if the serial output data port between the last driver IC is connected to the data port of the output interface or short circuited.
4. Whether the output signals are short-circuited to each other or short-circuited to the ground.
5. Check if the output cable is good.

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