2. When the module is not on, the transmission is normal: the solution to protect the circuit damage can short-circuit the 4 pins and 5 pins of 74HC 138.
3. One line is not lit every three lines: 4953 is damaged (one of them).
4. One line lights up every other line: For the problem of signal A, please check whether there is any virtual welding between 74HC245 and 74HC 138; A multimeter can be used to measure whether the voltage at the 1 pin of 74HC 138 is equal to about 2.5V If it is replaced, 74hc138; Carefully measure the path of ICA signal in the golden needle belt.
5. Two lines are lit every two lines: For the problem of signal B, please check whether there is any virtual welding between 74HC245 and 74HC 138; You can use a multimeter to measure whether the voltage at the second pin of 74HC 138 is equal to about 2.5V If it is replaced, 74hc138; Carefully measure the path of ICA signal in the golden needle belt.
6. Whether the upper half board is normal and the lower half board is fully on or not: If this is the case with T08A interface, it is necessary to check whether the next 8 DR data signals are connected. If it is normal, replace 74HC245 first; if it is not normal, replace 74HC595 first.
7. The STB and CLK signals of the upper and lower boards of this board are the same, and the data are separated (1 if it is the data of T 12 interface). If T08A plate is inspected as the upper half plate and the lower half plate, it should be inspected separately.
8. If there is a 1 lamp on the board, check whether there is virtual welding and replace this lamp.
9. There are four lights that are not lit vertically: one is to check whether there is virtual welding in 74HC595; Second, replace 74HC595；; Third, replace the lamp.
10. Three of the four vertical lights are off. 1 Normal: Replace the normal lights.
1 1. If the module displays an exception from a middle or other location; Check the data signal path; Replace the last normal display control light of 74HC595; If the abnormal light control of the first 74HC595 is not ruled out. Each 74HC595 controls 8-point width *4-point height lamps. The 74HC595 is connected in series with the DR data signal, that is, the DR signal enters the 14 pin of the next 74HC595 from the 14 pin of the 74HC595 to the last 74HC595. For example, the DR data of this board is amplified from needle to 74HC345 to UR 1 to UR2 to UR3 to UR8 and then output to the needle.
12. Sometimes when debugging the whole screen, the display from the front-end module to the back-end module is abnormal, and the general fault is that the cable is not plugged in properly or damaged; You can also use a slightly longer line to plug the line of the module you are looking for below into the abnormal module above to see how it is displayed, or you can connect the output of the normal module in front of the abnormal position above to the next row of modules to see how it is displayed and which module is out of order.