How to repair LED display _LED display repair Daquan?
LED display problems how to repair? Believe
After you read this article there will not be a small problem display screen will not bother you.
LED display fault analysis and solutions:
Fault analysis is the most direct for beginners, the most effective way is to exclude the law, the display is mainly composed of three major hardware: control card, cell board, switching power supply.
First of all: we determine the control card is not good, you look under the power to open the control card light is lit, if not under the check to see if there is 5V power supply, the display is not able to display the content, as long as the display content , Indicating that the control card display content is good; then you use the control card software to find the control card, if you can find that the control card to send the content of the function is good, if you can not find, you look under the communication line there Well, if you pick up, it may be a card problem. As long as these two functions are good, the control card is good, otherwise it is necessary to replace the control card.
Second, we have to determine the power is not good, if the power is broken, it will directly cause a few boards at the same time off or not normal, because a power supply is controlled at the same time several boards, that is, your display if Is in the same small area of several boards do not display or display is not normal, you should consider whether the power is broken, the most direct test method is to take a multimeter to measure the DC voltage file output voltage is between 4.9 ~ 5.5V. If it is necessary to replace the power.
Finally: we have to determine the cell board is not good, the display signal is sent from one cell board output pin to another board input signal, so a board has problems, will cause it behind the entire row does not light or abnormal , So when there is a problem in a row of displays, we should replace this row of abnormal starting board, or use the long cable to skip the board, look at the back of the board is normal.
One. Unit board failure analysis
A. There is a problem with the output
1, the detection output interface to the signal output IC line is connected or short circuit.
2, check the output clock latch signal is normal.
3, Check whether the output data port of cascade connection between the last driver IC and the data port of the output interface is connected or short-circuited.
4, the output signal is short-circuited or short-circuited to ground.
5, check the output cable is good.
B. all bright one or a few lines does not shine
1, the detection of 138 to 4953 between the circuit is open circuit or Weld, short circuit.
C. The whole board is not bright
1, check the power supply and signal line is connected.
2, Check whether the test card to identify the interface, the test card flashing red did not identify, check the light board with the test card with the power, or light board interface has a signal and ground short circuit can not identify the interface. (Smart test card)
3, 74HC245 detect whether the solder joint short circuit, 245 corresponding to enable (EN) signal input and output pin is Weld or short circuit to other lines.
Note: The main check power and enable (EN) signal.
D. point oblique scan, the regular interlaced does not shine the screen overlap
1, check A, B, C, D signal input port to 245 for disconnection or Weld, short circuit.
2, Detect 245 corresponds to the A, B, C, D output and 138 whether the open circuit or Weld, short circuit.
3, detect A, B, C, D between the signal is short circuit or a short circuit between the signal.
Note: The main test ABCD line signal.
E. Confusion, but the signal output to the next board is normal
1, Detect 245 corresponding STB latch output terminal and drive IC latch terminal is connected or the signal is short-circuited to other lines.
F. full light when one or a few columns are not bright
1, Find the pin controlling the column on the module, and measure whether the output of the driver IC (74HC595 / TB62726 ,,,) is connected.
G. There is a single or single highlight, or the entire line is highlighted and uncontrolled
1, check whether the column is short-circuited with the power supply.
2, test whether the line is short-circuit with the positive power supply.
3, replace its driver IC.
H. display confusion, the output is not normal
1, check the clock CLK latch STB signal is short circuit.
2, detect whether the clock CLK 245 input and output.
3, the detection of the clock signal is shorted to other lines.
Note: The main test clock and latch signal.
I. shows lack of color
1, the detection 245 of the color of the data end whether there is input and output.
2, testing the color of the data signal is short-circuited to other lines.
3, the detection of the color of the drive IC between the cascade data port is open circuit or short circuit, Weld.
Note: The voltage detection method can be used to find problems more easily. The voltage at the detection port is different from the normal one to determine the fault area.
J. All-light when there is a single point or more (irregular) does not shine
1, find the module corresponding to the control pin measurement is short circuit with the Bank.
2, replace the module or a single lamp.
K. in the line scan, two or more lines (usually a multiple of 2, regular) lit at the same time
1, A, B, C, D detect whether the signal between the short circuit.
2, check if the 4953 output is short-circuited with other outputs.
L, all LEDs are off: the total power is not turned on; some LEDs are off: the polarity of the output of the switching power supply is reversed or the connection of the module is disconnected;
All LEDs are dim: too many LEDs are loaded or module polarity is reversed; some LEDs are dim and lamp bead is hot: module is shorted; LED brightness is not
Consistent: too many LEDs are loaded
LED flashes: bad line contact; burn insurance: short circuit at the module or wiring.
