What should I do if the LED screen has no signal

There is no input signal after the LED screen is powered on:
1. Check the VGA cable connection.
2. Check the circuit from the line field input of the main board (pay attention to whether there is a short circuit between the line field of the VGA socket and the ground) to the inverter output and then to the circuit of the main chip (whether there is a virtual welding short circuit, and whether the capacitor and resistance values are wrong? ).
3. Check the voltage of each working point of the main board (maybe the main chip is damaged).

After the LED screen is turned on, the display exceeds:
1. Check whether the computer input signal is out of range.
2. Check the voltage of each working point of the motherboard (maybe the main chip is damaged).
3. Whether the "phase" can be adjusted by automatic adjustment or manual adjustment.
4. Check the voltage of each working point of the main board (maybe the main chip is damaged).
5. Check whether the capacitance and resistance of the phase-locked loop have wrong values
6. Check the circuit from the line field input to the inverter output to the main chip (whether there is a virtual welding short-circuit capacitor resistance, and whether there is an error value). Enbon