1, observation method
    The use of sight, smell, and touch. When the damaged components will change, blistering or burning spots; burning device will produce some special smell; short circuit will be hot; can also be observed at the weld or sealing with the naked eye.
    2, percussion
    Often instrument running when the bad phenomenon, the vast majority of this phenomenon is due to bad contact or by. In this case, tapping and hand pressing can be used.
    The so-called "stroke" is the possible fault location, through a small rubber hammer or other things lightly on the board or percussion parts, to see whether caused by error or malfunction. The so-called "hand pressure" is that when the fault occurs, turn off the power supply, insert the components and plug and seat again with the hand firmly, and then boot to try whether it will eliminate the fault. If you find that knocking on the casing is normal, and then beat and not normal, it is best to put all the joints re inserted, try again, if the nerve is not successful, we have to think of another way.
    3, replacement method
    Requires two instruments of the same type or with sufficient spare parts. Replace a good spare part with the same component on the fault machine to see if the trouble is eliminated.
    4. Exclusion
    The so-called exclusion method is by some device plug-in board, plug inside the machine to determine the cause of the malfunction. When a plug-in board or device is removed, the instrument returns to normal, indicating that the fault occurred there.
    5, lifting temperature method
    Sometimes, the instrument work for a long time, or in the summer when the work environment temperature is higher, there will be a fault, shutdown, check normal, stop for some time, and then boot and normal, after a while there is a fault. This phenomenon is due to the poor performance of individual IC or components, and the high temperature characteristic parameters can not meet the requirements of the index. In order to find out the cause of the fault, the metal processing network can adopt the lifting temperature method.
    The so-called cooling, that is, in the case of failure, with cotton fiber will be anhydrous alcohol in the parts may fail to wipe, so that it cools, to observe whether the failure is eliminated. The so-called "warming" is to artificially raise the temperature of the environment, such as the use of electric iron placed near the suspect parts (note that the temperature can not be raised too high to damage the normal device) to see if the failure occurred.
    6, contrast method
    We require two units of the same type and one of them is in normal operation. This method requires the necessary equipment, such as a multimeter, an oscilloscope, and so on. According to the nature of the comparison, there are voltage comparison, waveform comparison, static impedance comparison, output comparison, current comparison and so on.
    The specific method is to make the faulty instrument and the normal instrument run in the same situation, and then detect the signals of some points, and compare the two groups of signals measured. If there is any difference, then it can be concluded that the fault is here. This approach requires the maintenance personnel to have considerable knowledge and skills.
    7, riding shoulder method
    Shoulder riding is also called parallel method. The IC chip is a good safety to check on the chip, or good components (resistors and capacitors, diodes and transistors) and parallel components to check, maintain good contact, if the reasons for failure from the device internal circuit or poor contact, then this method can be used to exclude.
    8, isolation law
    The fault isolation method does not require the same type of equipment or spare parts for comparison, and is safe and reliable. According to the flow chart of fault detection, the method of splitting and encircling, gradually reducing the scope of fault search, and combining signal contrast and component exchange will find the fault quickly.
    9 capacitor bypass method
    When a circuit produces strange phenomena, such as a display disorder, the capacitor bypass method can be used to identify the faulty circuitry. Connect the capacitor across
    10, the state adjustment method
    Generally speaking, before the fault is not determined, do not touch the components in the circuit, especially the adjustable type device, even more so, for example, potentiometers, etc.. However, if the reference measure is taken in advance (for example, the location mark or voltage value or resistance value of the instrument is not touched before it is touched), it is still allowed to be touched if necessary. Maybe after the change, sometimes the fault will be eliminated.
    The power supply and the ground terminal of the IC are connected to the base input end or the collector end of the transistor circuit to observe the influence on the fault phenomenon. If the capacitor bypass input is invalid and the fault is passed through its output, the fault is determined in this circuit.

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