12 steps to solve common faults of LED display unit board!

Publisher: Supplier of LED Display Time: 2022-11-24 17:03 Views: 508

We often encounter LED display unit board failures, so how to solve the failures we encounter? Next, Liancheng will teach you 12 steps to solve the common faults of the display unit board. details as follows:


1. The whole board of the LED display is not bright: the board is not connected to the power supply; the input cable is reversed; the input and output are reversed; the positive and negative poles of the power supply are reversed.


2. The LED display board is off and the transmission is normal: the protection circuit is damaged. The solution is to short-circuit pin 4 and pin 5 of 74HC138.


3. One of the three lines of the LED display is not lit: 4953 is damaged (one of them is damaged).


4. The LED display lights up one row at a time: A signal problem, please check whether there is any solder joint between 74HC245 and 74HC138; you can use a multimeter to measure whether the voltage of pin 1 of 74HC138 is equal to about 2.5V, if so, replace 74HC138; carefully measure the gold needle with ICA The path of the signal.


5. The LED display screen lights up two lines apart: B signal problem, please check whether there is any solder joint between 74HC245 and 74HC138; you can use a multimeter to measure whether the voltage of pin 2 of 74HC138 is equal to about 2.5V, if so, replace 74HC138; carefully measure the gold needle belt Pathway of ICA signal.


6. The upper half of the LED display is normal and the lower half is fully bright or not: If this is the case with the T08A interface, it is necessary to check whether the DR data signal of the lower 8 lines is connected. If it is normal, replace the 74HC245 first, and then replace it if it is not good. The first 74HC595.


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7. The STB and CLK signals of the half board and the lower half board of this board are common, and the data is separated (if it is T12 interface data, there is also one). For example, if checking the T08A board, the upper and lower half boards should be inspected separately. the


8. If one light on the board does not light up: check whether there is a weak soldering, and replace the light tube. the


9. There are 4 vertical lights on the LED display that do not light up: first check whether the 74HC595 has solder joints; second, replace the 74HC595; third, replace the lamp tube. the


10. Of the 4 vertical lights on the LED display, 3 are off and 1 is normal: replace the normal light tube. the


11. If the board displays abnormally from the middle or other positions backward: check the data signal path; replace the last 74HC595 that normally displays the control light; if it is not ruled out, replace the 74HC595 that is controlled by the first abnormal display light. Each 74HC595 controls 8 dots wide * 4 dots tall lamps. The 74HC595 is connected in series with the DR data signal, that is, the DR signal is connected from the 14th pin of the 74HC595 to the 9th pin and then connected to the 14th pin of the next 74HC595 to the last 74HC595. For example, the DR data of this board is from the gold pin to the 74HC345 After zooming in, go to UR1 to UR2 to UR3 until UR8 and then to the output gold needle. the


12. Sometimes in the process of debugging the whole screen, the display from the front module to the rear module is abnormal. The general fault is that the cable is not plugged in or damaged; you can also use a slightly longer cable to arrange the module being checked below. Plug the cable into the abnormal module above to see how it is displayed. You can also connect the output of the normal module above the abnormal part to the next row of modules to see how it is displayed and which module has the problem.


LED display common troubleshooting and solutions:


Unit board failure:


A. The whole board is not bright


1. Check whether the power supply and signal line are connected.


2. Check whether the test card is used to identify the interface. If the red light of the test card flashes, there is no identification. Check whether the light board and the test card have the same power supply ground, or there is a short circuit between the signal and the ground of the light board interface, which makes the interface unrecognizable. (Smart Test Card)


3. Check whether the 74HC245 is short-circuited or not, and whether the corresponding enable (EN) signal input and output pins on the 245 are soldered or short-circuited to other lines.


Note: Mainly check the power supply and enable (EN) signal.


B. During dot oblique scanning, the regular interlaced non-light display screen overlaps


1. Check whether there is any disconnection, virtual welding, or short circuit between the A, B, C, and D signal input ports and 245.


2. Check whether the corresponding A, B, C, D output terminals of 245 and 138 are disconnected, welded or shorted.


3. Detect whether the signals of A, B, C, and D are short-circuited or whether a signal is short-circuited to ground.


Note: Mainly detect ABCD line signals.


C. One or several lines are not bright when all lights are on


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


D. During line scanning, two or several lines (usually a multiple of 2, regularly) light up at the same time


1. Detect whether there is a short circuit between the signals of A, B, C, and D.


2. Check whether the output terminal of 4953 is short-circuited with other output terminals.


E. There are single or multiple points (irregular) not bright when fully bright


1. Find the corresponding control pin of the module and measure whether it is short-circuited with the bank.


2. Replace the module or single lamp.


F. One column or several columns are not bright when all lights are on


1. Find the pin that controls the column on the module, and check whether it is connected to the output terminal of the driver IC (74HC595/TB62726,,,).


G. There is a single point or a single column highlighted, or the entire row highlighted, and it is not controlled


1. Check if the column is shorted to power ground.


2. Check if the row is shorted to the positive pole of the power supply.


3. Replace its driver IC.


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


1. Detect whether the STB latch output terminal corresponding to 245 is connected to the latch terminal of the driver IC or whether the signal is short-circuited to other lines.


I. The display is confused and the output is abnormal


1. Detect whether the clock CLK latches the STB signal is short-circuited.


2. Check whether the clock CLK of 245 has input or output.


3. Check whether the clock signal is short-circuited to other lines.


Note: Mainly detect clock and latch signals.


J. Display lack of color


1. Check whether there is input or output at the data end of the color of 245.


2. Detect whether the data signal of the color is short-circuited to other lines.


3. Check whether the cascaded data ports between the driver ICs of this color have open circuit, short circuit, or false soldering.


Note: You can use the voltage detection method to find the problem more easily, check whether the voltage of the data port is different from the normal one, and determine the fault area.


K. There is a problem with the output


1. Check whether the line from the output interface to the signal output IC is connected or short-circuited.


2. Check whether the clock latch signal of the output port is normal.


3. Detect whether the cascaded 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 shorted to each other or shorted to ground.


5. Check whether the output cable is in good condition.


Full screen failure:


The whole screen is not lit (black screen)


1. Check whether the power supply is powered on.


2. Check whether the communication line is connected and whether there is any wrong connection. (synchronous screen)


3. The synchronization screen detects whether the green lights of the sending card and receiving card are flickering.


4. Whether the computer monitor is protected, or the display area of the display is black or pure blue. (synchronous screen)


The whole unit board is off (black screen)


1. If the horizontal direction of several boards is not bright, check whether the cable connection between the normal unit board and the abnormal unit board is connected; or whether the chip 245 is normal.


2. If the longitudinal direction of several consecutive boards is not bright, check whether the power supply of this column is normal.


The line on the unit board is not bright


1. Check whether the line pin is connected to the 4953 output pin.


2. Check whether 138 is normal.


3. Check whether 4953 is hot or burned.


4. Check whether 4953 has a high level.


5. Check whether the 138 and 4953 control pins are connected.


Unit board is not bright


1. Check whether 595 is normal.


2. Check whether the corresponding pins of the upper and lower modules are connected.


3. Check whether the 595 output pin is connected to the module pin.


Lack of color on the unit board


1. Check whether the 245 R.G data is output.


2. Check whether the normal 595 output pin is connected to the abnormal 595 input pin.


The above is the 12-step solution to the common faults of the display unit board compiled by the editor of Liancheng. I hope it will be helpful to everyone. Welcome to add or correct. Lianchengfa is a world-leading provider of LED display applications and solutions, as well as a national-level professional and special new small giant enterprise. The main business covers four major sections: "Smart City", "Cultural Tourism Commercial Performance", "Commercial Display Engineering", and "Content Technology". It has the world's leading automated production equipment, modern post-doctoral research laboratories and comprehensive sales and services. team. Friends who want to buy LED displays can also contact us Lianchengfa led display manufacturer, a big country brand, trustworthy!