1. The whole board does not light up: the board is not connected to the power supply; the input cable is plugged in reverse; the input and output are reversed; the positive and negative poles of the power supply are reversed (reverse connection will burn all the ICs on the board). (LED display)
2. The board is off and the transmission is normal: The protection circuit damage solution can short-circuit the 4th and 5th pins of the 74HC138.
3. One line does not light up every other three lines: 4953 is damaged (one of them is damaged).
4. Light on every other line: A signal problem, please check whether 74HC245 and 74HC138 have false welding; you can use a multimeter to measure whether the voltage of the first pin of 74HC138 is equal to about 2.5V, if there is any replacement 74HC138; carefully measure the gold needle with ICA signal path Happening.
5. Light on two lines every other line: B signal problem, please check whether 74HC245 and 74HC138 have false welding; you can use a multimeter to measure whether the voltage of the second pin of 74HC138 is equal to about 2.5V, if there is any replacement 74HC138; carefully measure the gold needle with ICA signal Access conditions.
6. The upper half board is normal and the lower half board is all on or off: if this is the case with the T08A interface, this is to check whether the DR data signal of the next 8 lines is channeled, if it is normal, replace 74HC245 first, if not, replace the first one. 74HC595.
7. The STB and CLK signals of the half board and the lower board on this board are common, and the data is separated (if it is a T12 interface data, it is also one). If checking the T08A board, the upper and lower halves should be checked separately.
8. If one lamp on the board does not light up: check whether it is soldered and replace the lamp.
9. There are 4 lamps that are standing upright: the first is to check whether the 74HC595 has false welding; the second is to replace the 74HC595; the third is to replace the lamp.
10. Among the 4 lamps standing upright, 3 lamps are off and 1 lamp is normal: replace the normal lamp. (LED display)
11. If the board displays abnormally from the middle or other positions backwards: check the data signal path; replace the 74HC595 with the last normal display control lamp; if not ruled out, replace the 74HC595 with the first abnormal display control lamp. Each 74HC595 controls 8 dots wide * 4 dots high tubes. The 74HC595 is connected in series with the DR data signal, that is, the DR signal goes from the 14th pin of the 74HC595 to the 9th pin and then connects to the 14th pin of the next 74HC595 to the last 74HC595. For example, the DR data of this board goes from the gold pin to the 74HC345 After zooming in, it goes from UR1 to UR2 to UR3 until UR8 to output the gold needle.
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 longer cable to check the module under investigation. Plug the cable into the abnormal module above and see how it is displayed. You can also connect the output of the normal module in front of the abnormal place above to the next row of modules to see how the display is, to determine which module is the problem. .
