(1) The voltage measurement method measures whether the working voltage of each key point is normal, which can quickly identify the fault point. For example, measuring the working voltage and reference voltage of the A/D converter.

(2) The sensory method directly determines the cause of the malfunction by relying on the senses. Through visual inspection, it can detect issues such as wire breakage, desoldering, short circuit of grounding wires, broken fuse tubes, burnt components, mechanical damage, copper foil warping and breakage on printed circuits, etc; You can touch the temperature rise of the battery, resistor, transistor, and integrated block, and refer to the circuit diagram to identify the cause of abnormal temperature rise. In addition, you can also check by hand whether the components are loose, whether the integrated circuit pins are securely inserted, and whether the transfer switch is stuck; Can be heard and smelled for any abnormal sounds or odors.

(3) The circuit breaker method disconnects the suspicious part from the entire machine or unit circuit. If the fault disappears, it indicates that the fault is in the disconnected circuit. This method is mainly suitable for situations where there is a short circuit in the circuit.

(4) The short circuit method is generally used in the inspection of A/D converters mentioned earlier, which is more commonly used in repairing weak and micro electrical instruments.

(5) When the fault has narrowed down to a certain location or several components, online or offline measurement can be carried out using the measuring element method. If necessary, replace with good components. If the fault disappears, it indicates that the component is damaged.

(6) The interference method uses human induced voltage as the interference signal to observe the changes in the LCD display, and is commonly used to check whether the input circuit and display part are intact.