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The working principle and fault maintenance of the LED display are “much the same”

2023-11-24 23:10:13

1. Module signal introduction
1. Supply voltage: DC5V
2, data interface mode: T12, 8 rows per zone, 8 columns per zone, data, OE high efficiency.
3, input signal: A, B, OE, DR, STB, CLK, GND
4, Input signal introduction: A and B are scanning signals (this module is 1/4 scan), OE is enabled, DR Is data, STB is latch, CLK is clock, GND is ground (negative power supply)

Second, IC introduction (can go to the Internet for details)
1, U1 is 74HC245, U2 and U3 are 4953, U4 is 74HC138, UR1-UR16 is 74HC595
2, 74HC245 function is to amplify the signal, all the input signals must pass through this IC. Sometimes the whole board has problems or does not transmit there may be damage to this IC or solder.
3, 4953 function is the control line, if the board horizontal direction fault and is the whole line is generally the fault of this IC. 1 piece 4953 controls 8 rows.
4, 74HC138 function is to control the scan, input A, B and OE signal output 4 signals to control 2 pieces 4953.
5, 74HC595 function is displayed in the control column, input STB, CLK and DR Signal output 8 signals to control 8 lamp width *4 lamp height.

Outdoor module failure maintenance (P10-1R as an example)
1, the whole board is not bright: the board is not connected to the power supply; The input bar is inserted inversely; Input and output are reversed; The positive and negative terminals of the power supply are reversed (the reverse connection will burn all ics on the board).
2, the board is not bright transmission normal: protection circuit damage solution can be 74HC138 foot 4 and foot 5 short circuit.
3, every three lines there is a line is not bright: 4953 damage (is one of the damage).
4. Light one line after another: For the problem of A signal, please check whether 74HC245 and 74HC138 have virtual welding; Can use a multimeter 74HC138 first pin voltage is equal to about 2.5V, if there is a replacement 74HC138; Carefully measure the path of ICA signal on the gold tape.
5, after two lines bright two lines: B signal problem, please check 74HC245 and 74HC138 whether there is virtual welding; Can use a multimeter 74HC138 the second pin voltage is equal to about 2.5V, if there is a replacement 74HC138; Carefully measure the path of ICA signal on the gold tape.
6. The upper half board is normal and the lower half board is fully bright or not: If this is the case in the T08A interface, it is necessary to check whether the DR Data signal of the next 8 lines is in the channel. If the 74HC245 is normal, replace the first 74HC595 if it is not good.
7, the STB and CLK signals of the upper and lower boards of this board are common, and the data is separate (if it is T12 interface data is also 1). If the T08A board is checked, the upper and lower half boards should be checked separately.
8, if the board has a lamp is not bright: check whether the welding, replace the lamp tube.
9, there are 4 vertical lights are not lit: the first check 74HC595 whether there is virtual welding; The second replacement 74HC595; Third, replace the lamp.
10, in the vertical 4 lights, 3 trees are not bright and 1 tree is normal: replace the normal lamp tube.
11, if the board in the middle or other positions in the future display is abnormal: check the data signal path; Replace the 74HC595 of the last normal display control lamp; If not ruled out to replace the first display abnormal light control 74HC595. Each 74HC595 controls 8 point wide by 4 point tall tubes. 74HC595 is connected in series with the DR Data signal that is the DR Signal from the 14th pin of 74HC595 into the 9th pin to the 14th pin of the next piece of 74HC595 to the last 74HC595. For example, the DR Data of this board is amplified from gold needle to 74HC345, UR1 to UR2 to UR3, and UR8 to the output gold needle.
12. Sometimes in the process of debugging the whole screen, the front module to the back module is not displayed normally, and the general fault is that the line is not plugged or damaged; You can also use a slightly longer line to plug the following module line into the above abnormal module to see how the display is, and you can also connect the above abnormal place in front of the normal module output to the next row of modules to see how the display is, to determine what is the problem with the module.


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