How to Maintenance Small Pixel Pitch LED Display? (Part 2)

1. the led module appears a long bright, dark, not bright. Inspection and maintenance:

(1) visual inspection unit line on the tube leads feet Weld; if so, will be a good welding pin.

(2) with a multimeter to test the line tube output and the module feet are connected:

A. if not connected,connect with data cable.

B. if connected, then test whether and short circuit.

B-1. if no, measuring voltage (multimeter test method: Black pen connect GND, the red  pen to measure the voltage of each pin).

B-2. If so, then test the line output and the corresponding module pin circuit.

B-2-1. if not, measuring line tube input is normal.

B-2-2. If the HC138 output is not connected to the input of the line pipe; if not, then determine the HC138H bad.

If the above measurements are normal, there are quality problems of the 4953 line , repair with the same type line tube.

The effect of 4953: the line drive tube, power tube. It is two CMOS tubes, 1, 3 feet VCC, 2, 4 feet control foot, 2 feet control 7,8Pin output, 4 feet control the output of 5,6 feet, only when the 2,4 pin is "0", 7,8,5,6 will output, or the output is high impedance state.

2. the led module appears a long bright, dark, not bright. Inspection and maintenance:

(1) visual led module board corresponding to the fault on the module pin and integrated circuit is Weld, short circuit, open circuit; If so, the pin is welded.

(2) with a multimeter to measure the output voltage of the HC4953 is normal; If so, then determine the MBI5124 output and the module input circuit; if not, then determine the MBI5124 bad, with the same type MBI5124 integrated circuit MBI5124 replace the integrated circuit, pay attention to circuit leads do not disconnect.

3. the led module appears 32-point line, column or single point does not light, long bright, dark and 32 points. Inspection and maintenance:

(1) visual fault corresponding to the module pin and lead for short circuit, cold solder joint, open circuit.

(2) each cell (cell board is divided into upper and lower two cells) of the upper and lower, left and right modules are shared between the cable is normal (the multimeter with the adjacent side, measured. The amount of module line input and the control input of the lead connection), if so, then determine the module is bad, if not, can be directly replaced by fine data cable can be eliminated.

(3) can be used to directly measure a single multimeter module is normal, if so, then determine the circuit board and the module between the internal short-circuit.

4. the led module appears Not bright, longtime bright, dark bright on module several lines or whole area (module consist of two area “up”and “down”). Inspection and maintenance:

(1) visual inspection of the corresponding tube, through inductance, whether the integrated circuit Weld, short circuit, open circuit, if so, disconnect and short-circuit Weld, circuit re-welding.

(2) With a multimeter to measure the output voltage of each line tube is normal (multimeter measurement method: black table pen then GND, the red pen to measure the voltage of each pin); If so, then determine the line output and the corresponding module pin circuit; If not, measure the output of the corresponding HC138 is normal; If so, then determine the HC138 line of the output and the line of the importation of the line pipe is not the same; Terminal circuit; if not, then determine HC138 bad.

(3) with a good 16P cable replacement try to measure HC138 address input 1,2,3 pin voltage, strobe side 4,5 (active low), 6 (active high) and integrated circuits power supply is normal or not, if so, the determine HC138 bad, and then to (2) continued investigation.

(4) between the two districts of the 5V cable is disconnected or not, and if so, can be directly connected with the same power line (the general phenomenon is the whole area does not light, dark light).

(5) measurement module input signal line (16P can be regarded as 12 groups of which 2,4,6,8 feet, respectively, A, B, C, D, 4 groups of signals) with or without internal short circuit, open circuit and input HC245 after the drive is normal, if yes, then measure the HC245 drive input HC138 signal is normal or not , then (2) continued, if not, can determine HC245 bad, with the same type of integrated circuit replacement.