introduction In recent years, with the improvement of living standards, people are paying more and more attention to the health of themselves and their families, all kinds of simple and practical! Newly-featured new home medical electronic devices have emerged as the times require, and have entered the family and become an indispensable item in people's lives. With the development of electronic technology, automatic and semi-automatic home medical electronic instruments, such as electronic blood pressure monitors , low-frequency therapeutic devices, blood glucose testers, and electronic thermometers, have been introduced to the market, and are moving toward high, precise, sharp and intelligent. In addition to the increasing requirements for their own R&D and design, these products are increasingly demanding after-sales maintenance technology. From the perspective of its product structure, it is difficult to provide after-sales maintenance work for parts and components of various periods, such as transistors and integrated circuits. It is unsustainable for maintenance personnel to rely solely on the original failure analysis and maintenance methods, which puts higher requirements on the after-sales maintenance work of medical production enterprises. 1 Failure analysis Fault analysis is the key to judging and finding the cause of the fault. The faults are caused by factors such as the user, the environment and the instrument itself. For a faulty instrument, when there are some complicated and hidden faults, it is a very difficult and difficult task for beginners and those with certain maintenance experience. Because there are many kinds of instruments, their working principle and structural characteristics are different, so there are many kinds of faults and causes of the whole machine; in addition, even the same fault of the same instrument can have different causes. This is the difficulty in finding and judging the fault. Therefore, the fault finding and judging work is a technical and empirical work that is very difficult and difficult. However, the fault analysis of the instrument also has certain rules to be found, and the use of traditional Chinese medicine methods to analyze the cause of the fault is an effective method, which is described below. 1.1 "Ask" Chinese medicine means that the symptoms are ranked third. “The “question†in the failure analysis is in the first place. “Q†is to understand the background information of the fault, to understand in detail the whole process of the fault of the instrument, the history of the fault, Maintenance history and usage, to determine whether the cause of the fault is caused by human or natural factors, and provide the necessary clues for judging the fault. This mainly includes: What environment is used? What is the external performance of the failure? The process of asking is It is necessary to grasp the basic situation of the instrument, collect the necessary data for fault analysis, and also the need to locate the fault location by fault analysis. 1.2 "Wang" Chinese medicine refers to the color of the body. The "expectation" of fault analysis is to look at the damage of the instrument, to observe the appearance of the faulty board, to see if there are any obvious signs of damage, whether there are components burning black, bursting, whether the circuit board is broken or leaked due to corrosion. Whether there is leakage of electrolytic capacitors, whether there is any bulging at the top, whether the solder joints are disconnected, whether the mechanical transmission parts are malfunctioning or stuck, whether the waveform image is normal or not, etc., and the faulty parts can often be found through visual inspection. 1.3 "Smell" Chinese medicine means listening to the sound. The "smell" in the failure analysis is to use the nose to distinguish the analysis. Obtaining information while observing the faulty instrument, when "smell" smells the nose with a smell of burning charcoal in the circuit board, where the smell is emitted" generally has two meanings: one, Nasal sniffing its taste; Second, it smells after powering up. "If the instrument has burnt smell, it is caused by excessive current of a certain component. At this time, it must be shut down immediately to avoid expanding the fault. After the fault is found, the component can be replaced. Smell the sound, the general situation is abnormal after booting, should look for the part that emits abnormal sound, to find that some components have sparking phenomenon, especially the high pressure part. 1.4 "Cut" Chinese medicine refers to the pulse. The "cut" of fault analysis refers to the measurement, which is the method of measuring and analyzing the fault parts of the circuit by using various measuring instruments and means. "Cut" is an important method of fault analysis. It is the measurement of various data, such as voltage, frequency, waveform, and resistance value, and the difference between the observation and analysis parameters is to analyze the fault from the perspective of quantity. Based on the understanding and comprehensive analysis of the working principle of the instrument, the corresponding measures are taken to determine the source of the fault. Common "cut" tools are mainly digital multimeters, digital oscilloscopes, spectrum analyzers, etc. Commonly used measurement methods include parameter measurement method, principle measurement method, instrument self-test method, and comprehensive method. 1.4.1 Parameter measurement method The parameter measurement method usually uses a digital multimeter and other test instruments to measure the working voltage, static working current, ground resistance and component parameters in the line to determine the fault. Through the measurement, it can be known whether the CPU's working basic power supply, crystal oscillation, and reset voltage are established. Whether the output voltage is normal, whether there is overcurrent, and whether the circuit is unobstructed. For example, at a certain time, a certain level of the data waveform, pulse width and amplitude, time relationship and other parameters, combined with the specific unit circuit and circuit board, logical reasoning analysis. 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Home medical electronic instrument failure analysis and maintenance