The 12 common problems of LED display modules are introduced in detail as follows:
1. The entire LED display module does not light up
The power supply is not connected; the input cable is plugged in reverse; the input and output are reversed; the positive and negative poles of the power supply are connected in reverse.
2. The module does not light up and the transmission is normal
The solution is that the protection circuit is damaged and the 4th and 5th pins of 74HC138 are short-circuited.
3. One row of the module does not light up every three rows
4953 is damaged (one of them is damaged).
4. The module lights up every other row
A signal problem, please check whether there is a cold soldering between 74HC245 and 74HC138; you can use a multimeter to measure whether the voltage of the 1st pin of 74HC138 is equal to about 2.5V. If it is, replace 74HC138; carefully measure the path of the gold needle with ICA signal.
5. The module lights up two lines every other line.
B signal problem, please check whether there is a cold solder joint between 74HC245 and 74HC138; you can use a multimeter to measure whether the voltage of the second foot of 74HC138 is equal to about 2.5V. If it is, replace 74HC138; carefully measure the path of the gold pin with ICA signal.
6. The upper half of the module is normal and the lower half of the module is all lit or not.
If the T08A interface has this situation, you should check whether the DR data signal of the next 8 lines is connected. If it is normal, replace 74HC245 first. If it is not good, replace the first 74HC595.
7. The STB and CLK signals of the upper and lower parts of the module are common, and the data is separated (if it is a T12 interface, the data is also 1). If you check the T08A board, the upper and lower halves should be checked separately.
8. If one lamp of the module is not lit, check whether there is a poor soldering and replace the lamp.
9. If there are 4 lamps that are not lit vertically, first check whether the 74HC595 has a poor soldering; second, replace the 74HC595; third, replace the lamp.
10. Among the 4 lamps in the vertical position, 3 are not lit and 1 is normal.
Replace the normal lamp.
11. If the module displays abnormally from the middle or other positions, check the data signal path; replace the last 74HC595 that controls the normal display lamp; if it is not ruled out, replace the 74HC595 that controls the first abnormal display lamp. Each 74HC595 controls 8 dots wide * 4 dots high lamps. The 74HC595 is connected in series with the DR data signal, that is, the DR signal enters from the 14th pin of the 74HC595 and exits from the 9th pin to the 14th pin of the next 74HC595 and reaches the last 74HC595.
12. Sometimes when debugging the entire screen, the display of the front module to the back module is abnormal. Generally, the fault is that the cable is not plugged in properly or is damaged. You can also use a slightly longer cable to plug the cable of the module being checked below to the abnormal module above to see how it displays. You can also connect the output of the normal module in front of the abnormal one above to the next row of modules to see how it displays.