2. The whole unit board is black

A: If several consecutive boards are not in the horizontal direction, check whether the connection between the normal unit board and the abnormal unit board is connected. If several consecutive boards are not lit in the vertical direction, check if the power supply of this column is normal.

B: Check if the position of a receiving card is not lit, check if the receiving card voltage is 5V, and whether the network cable input to the receiving card is normal.

C: If a unit board is not lit, check if the cable input to the unit board is loose.