Explain the bad phenomenon of LED display screen and the solution

- May 15, 2019-

Remarks on treatment methods for adverse phenomena and causes

The whole screen is not bright no electricity or no signal

1. Whether the power supply is connected with the signal line

2. Check whether the test card identifies the interface, while the test card fails to identify when the red light flashes. Check whether the lamp board is at the same power supply ground as the test card, or the interface of the lamp board has signals and short-circuit to the ground, so the interface cannot be identified

3. Check whether 74HC245 has virtual welding short circuit, and whether the enable (EN) signal input and output pin on 245 has virtual welding or short circuit to other lines.

4. Check for any broken or short circuit of various signals, mainly for power supply and enable (EN) signals.

Display missing color broken or short circuit

1. Check whether there is a wire break or short circuit between 74HC245 banding belts.

2. Check whether the driver chip from 74HC245 is disconnected or short-circuited with other signals. It is easier to find the problem by using the voltage detection method

Display confusion, but output to the next board signal normal clock (CLK) or latch (STB) signal short circuit

1. Check whether the clock (CLK) or latch (STB) signal of 74HC245 input and output is short-circuited.

2. Remove the chip to identify the chip or PCB hole short circuit.

3. The circuit that can follow the signal can be searched down to detect whether the clock CLK of 245 has input and output

Full screen overlight blanking signal (OE) short circuit

1. Check whether 74HC245 input/output blanking (OE) signals are short-circuited or broken mainly in outdoor static full-color

2. Check whether the adjustable resistance of this color is virtual welding.

3. Check whether the limiting resistance of the 23rd pin on the driver chip (TB62726/YZ5026) is short in the VCC of the 24th pin

There is a small piece of blind spot welding in a PCB board

When the light is fully on, single or multiple points (irregular) will not light up, and the light will die. The short wire shall be adjusted to the short circuit file with a multimeter to check whether the light is short-circuited to the positive and negative poles, and whether the parameters are too low, and whether the parameters are connected with the pin chip control are too low to change the light