With the continuous expansion of the application scope of LED display screen, LED display enterprise not only has many new products, but also has joined many new people in the LED industry. However, for such a professional product as LED display screen, novices will be at a loss if they encounter screen failure. Don't worry! Today, this article will briefly introduce the causes of LED display failure, detection methods and solutions.



Factors causing failure of LED display screen



80% of the failures of LED display are caused by the following factors: AC distribution wiring harness, terminals, connectors, signal and low voltage DC connection wiring harness and connectors, switching power supply module, fan, plastic shell components. If these interfaces, cables, power supply and chassis are not selected properly, the whole or partial black screen, flower screen, mosaic, no signal and so on will be caused. These are also very difficult to maintain, so we pay attention in the production process to reduce the failure rate.



Another 80% of the other faults are caused by the following reasons: solder joints, capacitors, terminals on PCBA, LED lights, leaky dust accumulation caused by insufficient protection level of the box, hardware rust of leaky screw, control board and card. These reasons will lead to blind lights or high lights, one or more lines not bright, lack of color, etc. If the control card or software problems will lead to abnormal image display. The outdoor LED display screen must be designed strictly according to the detection standard, waterproof and dust-proof, wind and high temperature resistance, otherwise it is easy to have various faults, and even the whole LED display screen will be scrapped. In addition, the operator of the display screen should master the relevant basic knowledge, have good use habits, plus professional maintenance personnel, can also reduce the failure rate to a certain extent.



Fault detection of LED display screen



1. Resistance detection method, which adjusts the multimeter to the resistance gear, detects the resistance value from one point of a normal circuit board to the ground, and then detects whether the same point test of another same circuit board is different from the normal resistance value. If not, the scope of the problem is determined.



2. Voltage detection method, which adjusts the multimeter to the voltage level, detects the voltage to ground at a point of the circuit suspected of having a problem, compares whether it is similar to the normal value, or determines the scope of the problem.



3. Short-circuit detection method, the multimeter will be adjusted to short-circuit detection block (some are diode voltage drop gear or resistance gear, generally with alarm function), to detect whether there is a short-circuit phenomenon, found that short-circuit should be resolved first, so that it does not burn other devices. This method must be operated when the circuit is cut off to avoid damaging the meter.



4. Voltage drop detection method, the multimeter to the diode voltage drop detection file, because all IC is composed of many basic components, only miniaturized, so when a pin of its current through, there will be a voltage drop on the pin. Generally, the voltage drop on the same IC pin of the same type is similar. According to the voltage drop on the pin, it must be operated when the circuit is powered off. This method has some limitations, such as the high resistance of the detected device, it can not be detected.



Faults and Solutions

1. The whole screen is not bright or there are squares



Inspection:



1. Control whether the host is in good condition

2. Is the communication line plugged in properly?

3. Is the sending card inserted properly?

4. Is the data line between the multimedia card and the sending card of the acquisition card well connected?

5. Whether the position of the receiving card JP1 or JP2 switch is correct



Commissioning:



1. Turn on the main engine.

2. Plug in the communication line

3. Re-insert the sending card

4. Connect many media cards with acquisition cards and data lines between sending cards.

5. Adjust the position of JP1 JP2 switch



2. The control system cannot be found every time the LED studio is started.



Question:



1. Signal Acquisition Line Between COM Port and Data Transmitting Card

2. No connection or the 2COM port of the computer itself is broken



Solution: Connect the data line or replace the computer



3. Full screen with 16 rows of data flashing or always brightening



1. Check the settings in the LED studio

2. Open the LED studio, open debugging-settings, and set the row order to + 0 or + 1 or ghosting.



IV. Screen Shaking



Inspection:



1. Check the communication line between the computer and the big screen

2. Check the DVI line of multimedia card and sending card

3, send card bad



Commissioning:



1. Re-insert or replace the communication line

2. Pushing and inserting DVI wires for reinforcement

3, change the sending card.



5. One Unit Plate is not Bright



Inspection:



1. +5V Electricity or GND Supply

2. +5V and GND Short Circuit

3. Is there OE signal in 138 fifth leg?

4. Whether the OE signals connected to 245 are normal (open or short circuit)



Commissioning:



1. Give + 5V or GND

2. Disconnect the short circuit

3. Supply OE signal

4. Connect the break to disconnect the short circuit



6. The half part or the bottom part of the unit board is not bright or showing abnormally.



Inspection:



1. Whether the 5th leg OE signal of 138 is present or not;

2. Whether the signal of the 11th and 12th legs of 74HC595 is normal; (SCLK, RCK)

3. Whether the connected OE signal is normal; (Break or Short Circuit)

4. Whether the SCLK and RCK signals connected with 245 double-row pins are normal; (Break or Short Circuit)



Commissioning:



1. Connect the OE signal

2. Connect SCLK and RCK signals

3. Connect the broken circuit

4. Disconnect the short circuit



7. Unbright or abnormal display of one line or corresponding module on the unit board



Inspection:



1. Check whether the pin of the line signal of the corresponding module is virtual or leaky;

2. Check whether the pin corresponding to TIP 127 or 4953 is disconnected or short-circuited with other signals.

3. Check whether the up and down resistance of the line signal are not welded or leak welded.
4. Whether the output line signal of 74HC138 is disconnected or short-circuited with the corresponding TIP127 or 4953
Solve:
1. Welding the virtual and leaky welds well
2. Connect the circuit breaker well and disconnect the short circuit
3. Make up the unwelded supplies and weld the leaky ones well.
4. Connect the circuit breaker well and disconnect the short circuit
Eighth, the unit board has two lines of light at the same time (when displaying text, one line is normal, one line is bright)
Inspection:
1. Check whether the two lines of signals corresponding to the module are short-circuited or not.
2. Check whether the output leg of 138, pull-down resistance and module and TIP127 are short-circuited.
Solve:
1. Disconnect the short circuit
9. The upper or lower part of the red or green color is not bright or abnormal.
Inspection:
1. Check whether the input pins are normal or short circuit with GND, +5V
2. Check whether the signal between input pin arrangement and 245 is normal (short circuit or open circuit)
3, IC245 bad
Solve:
1. Connect the broken circuit
2. Disconnect the short circuit
3, replace IC
10. All LEDs are not bright
1. No voltage output of switching power supply;
2. Whether the output wiring of switching power supply is correct or not;
11. The brightness of the display screen is very low and the display image is blurred.
Reason:
1. Error in sending card program;
2. The function card is not set correctly
Solve:
1. Restore the default setting of the sending card and save it.
2. Set the minimum brightness value of monitor screen to be over 80.
No loading or communication
Inspection:
1. Ensure that the hardware of the control system is powered on correctly.
2. Check and confirm that the serial line used to connect the controller is a straight line, not a cross line.
3. Check and confirm that the serial connection is intact and there is no loosening or falling off at both ends.
4. Choose the right product model, the right transmission mode, the correct serial number, the correct serial transmission rate by comparing the LED display control software and the control card selected by ourselves. Correctly set the address element and the serial transmission rate on the hardware of the control system according to the dial switch diagram provided by the software.
5. Check whether the jumper cap is loose or falling off; if the jumper cap is not loose, make sure that the direction of the jumper cap is correct.
Solution: If the load still fails after the above check and correction, please use the multimeter to measure whether the serial port of the computer or control system hardware connected is damaged to confirm whether it should be returned to the computer manufacturer or the control system hardware should be returned to the test.
13. The system prompts the words "Please connect the LED display controller"
Question: Many customers and friends directly download the "led display control system" from the "download center" on the company's website. After 20 minutes of installation, the word "please connect to the LED display controller" will appear. This is because the system did not detect the hardware of the broad control system during the test time.
Solution: At this time, please connect one end of the hardware of the LED display control system you purchased to the computer, the other end to the HUB distribution board, and the layout socket of the HUB distribution board to the interface of each unit of the LED display screen. After the connection is completed, the relevant parameters can be set into the "Settings Screen Parameters" in the "Settings". When the software is closed and reopened, the word "Connection Successful" appears above the software. At this time, the system has detected the hardware of the display control system, and can be used normally without time limit.
14. What does automatic or manual brightness regulation mean?
1. Brightness adjustment refers to the adjustment between the darkest and brightest display on the display screen, not the sensitization adjustment.
2. Automatic brightness adjustment is to automatically adjust the brightness from the control system of broad LED display screen to a predetermined brightness according to the different brightness that should appear in different time periods.
3. Manual brightness adjustment refers to the end-user's operation of a wide LED display control system to make the LED display reach a specified brightness.

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