The basic maintenance step (1) is to determine the type of HUB board used by the module or unit board, so that the interface definition of the cable can be the same, so that it can be found. (2) According to the different models of the module or unit board, send the corresponding program to the receiving card to ensure that the module and unit board are displayed under the correct program, which is the premise to find out the cause of the failure. Usually, the model of the module or unit board is printed on the PCB for easy searching. (3) Observe the phenomenon of modules or cell boards, and determine the initial faults, such as common string points and small squares. (4) Use a multimeter to find the fault, mainly using the above short-circuit detection method to detect the pin between the chip and the LED lamp. (5) If the problem is not solved, the cause of the failure should be analyzed again and necessary tests should be carried out. ruminate