This fault is generally caused by the signal loss of the LED display. The reasons for the signal loss are generally: 1. According to the direction of the wiring, the network cable connected to the receiving card of the normal display box and the receiving card of the black screen box itself cannot communicate with the signal. , Replacing the network cable can solve the problem. 2. The power supply connected to the receiving card fails, resulting in no power supply to the receiving card. In this case, replace the power supply and restore the wiring to the original state to solve the problem. 3. The receiving card itself is faulty, replace the receiving card to solve the problem.