How to repair LED display?
How to repair LED display?
Failure analysis and treatment of LED display problems:
Failure analysis for beginners is the most direct and effective method is the method of elimination, the display is mainly composed of three major hardware: LED control card, LED modules, LED power supply.
First of all: we judge the control card is not good, you first look at the power to open, the control card indicator is lit, if not bright look down to check whether the 5V power supply, the display is not able to display the content, as long as the content can be displayed, indicating that the control card to display the content of the function is good; and then you use the control card software to find out about the control card, if it can be found, indicating that the control card sends the contents of the function of a good, if not find, you look at the communication, you can see the control card is good. If you can not find, you look at the communication line is not connected, if connected, it may be a problem with the card. As long as these two functions are good, the control card is good, otherwise we have to replace the control card.
Secondly; we have to determine whether the power supply is good, if the power supply is bad, it will directly cause several boards at the same time is not bright or not normal, because a power supply is at the same time controlling a number of boards, that is, your display if it is in the same small area of several boards do not display or display is not normal, you should consider is not the power supply is bad, the most direct method of detection is to take the multimeter DC voltage file to measure the output voltage Whether between 4.9 ~ 5.5V. If so, we should replace the power supply.
Finally: we have to judge whether the unit board is good, the display signal is transmitted from the output pin of a unit board to the input signal of another board, so a board has a problem, it will cause the whole row behind it is not bright or abnormal, so when the display row has a problem, we should replace the board which is not normal at the beginning of this row, or use a long row of wires to jump over the board, and then look at the back of the board whether it displays normally. The following boards will show normal display.
LED module failure analysis
A. Output problem
1, test the output interface to the signal output IC line is connected or short-circuited.
2, detect the output port clock latch
signal is normal.
3、Detect 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, whether the output signals are short-circuited to each other or to ground.
5、Check whether the output line is good.
B. When the whole bright line or several lines do not light up
1, detect whether the line between 138 to 4953 broken or welded, short circuit.
C. The whole board does not light
1, check whether the power supply and signal lines are connected.
2, check whether the test card to identify the interface, the test card red light flashing is not recognized, check whether the light board and the test card with the same power supply ground, or the light board interface has a signal and ground short-circuit resulting in failure to identify the interface. (Intelligent test card)
3, test 74HC245 there is no welding short-circuit, 245 on the corresponding enable (EN) signal input and output pins are not welded or short-circuited to other lines.
Note: Mainly check the power supply and enable (EN) signal.
D. In the point diagonal scanning, regular interlining does not light up the display screen overlap
1. Check whether there are broken wires or false welds or short circuits between A, B, C and D signal input ports to 245.
2, detect whether there is broken wire or false welding or short circuit between A, B, C, D outputs corresponding to 245 and 138.
3、Detect whether there is a short circuit between A, B, C, D signals or a signal is short-circuited to ground.
Note: Mainly detect ABCD line signal.
E. Display confusion, but the output signal to the next board is normal
1. Detect whether the STB latch output corresponding to 245 is connected to the latch of the driver IC or the signal is shorted to other lines.
F. full light when one or more columns do not light up
1, on the module to find the control of the column of pins, test whether the driver IC (74HC595/TB62726,,,,) the output is connected.
G. There is a single point or a single column highlighted, or the whole line is highlighted, and is not controlled
1, check whether the column is short-circuited with the power supply ground.
2, check whether the row is short-circuited with the positive terminal of the power supply.
3、Replace the driver IC.
H. Display confusion, the output is not normal
1, detect whether the clock CLK latch STB signal is short-circuited.
2, detect whether the clock CLK 245 input and output.
3, detect whether the clock signal is shorted to other lines.
Note: Mainly detect the clock and latch signal.
I. Display lack of color
1、Detect whether there is any input/output of the data terminal of the color of 245.
2, detect the color of the data signal is shorted to other lines.
3, the detection of the color of the driver IC between the cascade of data port whether there is a broken or short circuit, false welding.
Note: You can use the voltage detection method is easier to find the problem, test the data port voltage is different from normal, to determine the fault area.
J. full light when there is a single point or multiple points (irregular) does not light up
1, find the module corresponding to the control foot measurement and whether the Bank short circuit.
2, replace the module or a single light.
K. In the line scanning, two lines or several lines (generally a multiple of 2, regular) lit at the same time
1, test A, B, C, D signal is short-circuited.
2, detect whether the 4953 output and other outputs are short-circuited.
L, all LEDs are not lit: the total power supply is not open; part of the LEDs do not light: switching power supply output wiring polarity reversal
Or the module connecting line has a broken circuit;
All LEDs are dim: the number of load LEDs is too many or the polarity of the module is reversed; part of the LEDs are dim and the lamp beads are hot: the wiring of the module is short-circuited; the brightness of the LEDs is inconsistent: the number of load LEDs is too many.
Uniformity: too many load LEDs
LED flickering: poor line contact; burn fuse: short circuit in module or wiring.
Failure analysis for beginners is the most direct and effective method is the method of elimination, the display is mainly composed of three major hardware: LED control card, LED modules, LED power supply.
First of all: we judge the control card is not good, you first look at the power to open, the control card indicator is lit, if not bright look down to check whether the 5V power supply, the display is not able to display the content, as long as the content can be displayed, indicating that the control card to display the content of the function is good; and then you use the control card software to find out about the control card, if it can be found, indicating that the control card sends the contents of the function of a good, if not find, you look at the communication, you can see the control card is good. If you can not find, you look at the communication line is not connected, if connected, it may be a problem with the card. As long as these two functions are good, the control card is good, otherwise we have to replace the control card.
Secondly; we have to determine whether the power supply is good, if the power supply is bad, it will directly cause several boards at the same time is not bright or not normal, because a power supply is at the same time controlling a number of boards, that is, your display if it is in the same small area of several boards do not display or display is not normal, you should consider is not the power supply is bad, the most direct method of detection is to take the multimeter DC voltage file to measure the output voltage Whether between 4.9 ~ 5.5V. If so, we should replace the power supply.
Finally: we have to judge whether the unit board is good, the display signal is transmitted from the output pin of a unit board to the input signal of another board, so a board has a problem, it will cause the whole row behind it is not bright or abnormal, so when the display row has a problem, we should replace the board which is not normal at the beginning of this row, or use a long row of wires to jump over the board, and then look at the back of the board whether it displays normally. The following boards will show normal display.
LED module failure analysis
A. Output problem
1, test the output interface to the signal output IC line is connected or short-circuited.
2, detect the output port clock latch
signal is normal.
3、Detect 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, whether the output signals are short-circuited to each other or to ground.
5、Check whether the output line is good.
B. When the whole bright line or several lines do not light up
1, detect whether the line between 138 to 4953 broken or welded, short circuit.
C. The whole board does not light
1, check whether the power supply and signal lines are connected.
2, check whether the test card to identify the interface, the test card red light flashing is not recognized, check whether the light board and the test card with the same power supply ground, or the light board interface has a signal and ground short-circuit resulting in failure to identify the interface. (Intelligent test card)
3, test 74HC245 there is no welding short-circuit, 245 on the corresponding enable (EN) signal input and output pins are not welded or short-circuited to other lines.
Note: Mainly check the power supply and enable (EN) signal.
D. In the point diagonal scanning, regular interlining does not light up the display screen overlap
1. Check whether there are broken wires or false welds or short circuits between A, B, C and D signal input ports to 245.
2, detect whether there is broken wire or false welding or short circuit between A, B, C, D outputs corresponding to 245 and 138.
3、Detect whether there is a short circuit between A, B, C, D signals or a signal is short-circuited to ground.
Note: Mainly detect ABCD line signal.
E. Display confusion, but the output signal to the next board is normal
1. Detect whether the STB latch output corresponding to 245 is connected to the latch of the driver IC or the signal is shorted to other lines.
F. full light when one or more columns do not light up
1, on the module to find the control of the column of pins, test whether the driver IC (74HC595/TB62726,,,,) the output is connected.
G. There is a single point or a single column highlighted, or the whole line is highlighted, and is not controlled
1, check whether the column is short-circuited with the power supply ground.
2, check whether the row is short-circuited with the positive terminal of the power supply.
3、Replace the driver IC.
H. Display confusion, the output is not normal
1, detect whether the clock CLK latch STB signal is short-circuited.
2, detect whether the clock CLK 245 input and output.
3, detect whether the clock signal is shorted to other lines.
Note: Mainly detect the clock and latch signal.
I. Display lack of color
1、Detect whether there is any input/output of the data terminal of the color of 245.
2, detect the color of the data signal is shorted to other lines.
3, the detection of the color of the driver IC between the cascade of data port whether there is a broken or short circuit, false welding.
Note: You can use the voltage detection method is easier to find the problem, test the data port voltage is different from normal, to determine the fault area.
J. full light when there is a single point or multiple points (irregular) does not light up
1, find the module corresponding to the control foot measurement and whether the Bank short circuit.
2, replace the module or a single light.
K. In the line scanning, two lines or several lines (generally a multiple of 2, regular) lit at the same time
1, test A, B, C, D signal is short-circuited.
2, detect whether the 4953 output and other outputs are short-circuited.
L, all LEDs are not lit: the total power supply is not open; part of the LEDs do not light: switching power supply output wiring polarity reversal
Or the module connecting line has a broken circuit;
All LEDs are dim: the number of load LEDs is too many or the polarity of the module is reversed; part of the LEDs are dim and the lamp beads are hot: the wiring of the module is short-circuited; the brightness of the LEDs is inconsistent: the number of load LEDs is too many.
Uniformity: too many load LEDs
LED flickering: poor line contact; burn fuse: short circuit in module or wiring.