(1) Observation method is the first key point in the maintenance judgment process, which runs through the entire maintenance process and is a basic, direct, and important method. When the set-top box malfunctions, do not turn on the power first. Open the machine casing and conduct a comprehensive inspection of the visible parts inside the machine to see if there are obvious damages such as burning, charring, blackening, and cracking in the components; Check whether the plug socket is loose, detached, disconnected, and whether the connections between various parts are normal; Check if there are any abnormal phenomena such as short circuits, pinching, etc. in the wire; Whether the indicator light and LED indicate normally; Whether the power fuse is normal; Whether the software and hardware configuration is normal (such as software version, parameter settings), etc. (2) The replacement method is a detection method that uses components or circuits with the same specifications and good performance to replace a suspected but inconvenient component or circuit on a faulty electrical appliance, in order to determine the fault. For faults that are difficult to diagnose and involve a large range of faults, the method of replacing parts can be used to determine or narrow the fault range (such as using good cards to replace suspected faulty cards) to determine the faulty component. When replacing a set-top box board (including an SM board, display and control board, power board, and motherboard), it is necessary to first check the connection wires, signal wires, etc. connected to the faulty board. Then, replace the suspected faulty board, replace the power supply part, and finally replace other related boards. Determine the board to be replaced first based on its failure rate, and replace the board with a high failure rate first. (3) The comparison method, comparison inference method, and replacement method are similar, that is, comparing the appearance, configuration, and operation phenomenon of good components with suspected faulty components. Two set-top boxes can also be compared to determine the differences in environmental settings and hard vegetable placement of the faulty set-top box, in order to identify the fault location. Comparative inference method is a simple and feasible inspection method that compares the DC voltage, in circuit resistance, and other parameters of normal and faulty set-top boxes of the same model one by one to identify differences and infer the location of the fault. This method is mainly applicable to repairing some set-top boxes without circuit diagrams. (4) The circuit breaker method, also known as the circuit breaker segmentation method, compresses the fault range by cutting off a certain circuit or welding open a certain component or wiring, and is a commonly used method to narrow the fault inspection range. For example, if the overall current of a certain electrical appliance is too high, the suspicious part of the circuit can be gradually disconnected. The fault will occur at the level where the current returns to normal after disconnection. This method is commonly used to repair faults such as excessive current and fuse burning