①Characteristics of resistance damage
Resistance is the largest number of components in electrical equipment, but it is not the component with the highest damage rate. Open circuit is the most common for resistance damage, it is rare for the resistance to become larger, and the resistance to become smaller is the most rare. Common ones include carbon film resistors, metal film resistors, wire wound resistors and insurance resistors. The first two types of resistors are the most widely used. One of the characteristics of their damage is the high damage rate of low resistance (below 100Ω) and high resistance (above 100kΩ). ) Is rarely damaged; second, when low-resistance resistors are damaged, they are often burnt and blackened, which is easy to find, while high-resistance resistors are rarely damaged. Wirewound resistors are generally used for high current limiting, and the resistance is not large. When cylindrical wire wound resistors are burnt, some will turn black or the surface will burst or crack, and some will have no traces. Cement resistors are a type of wire wound resistors, which may break when burned out, otherwise there will be no visible traces. When the fuse resistor is burned out, a piece of skin will be exploded on the surface, and some have no traces, but it will never be scorched or blackened. According to the above characteristics, you can focus on checking the resistance and quickly find out the damaged resistance.

②Characteristics of electrolytic capacitor damage
Electrolytic capacitors are used in large amounts in electrical equipment and have a high failure rate. Electrolytic capacitor damage has the following manifestations: one is the complete loss of capacity or the capacity becomes smaller; the second is slight or severe leakage; the third is the loss of capacity or the capacity becomes smaller and there is leakage. Methods to find damaged electrolytic capacitors are:
(1) Look: some capacitors will leak when they are damaged. There will be a layer of grease on the surface of the circuit board under the capacitor or even on the surface of the capacitor. This type of capacitor can no longer be used; some capacitors will bulge after damage. Can not continue to use;
(2) Touch: Some electrolytic capacitors with serious leakage will heat up after starting up, and even burn your hands when touched with your fingers. This type of capacitor must be replaced;
(3) There is electrolyte inside the electrolytic capacitor. Long-time baking will make the electrolyte dry and reduce the capacitance. Therefore, it is important to check the capacitors near the heat sink and high-power components. The closer they are, the damage may be possible. The greater the sex.

③The characteristics of damage to semiconductor devices such as diodes and triodes
2. The damage of triode is generally PN junction breakdown or open circuit, among which breakdown short circuit is the majority. In addition, there are two kinds of damage performance: one is the deterioration of thermal stability, which is normal when the machine is turned on, and soft breakdown occurs after a period of working time; the other is the deterioration of the characteristics of the PN junction, measured with a multimeter R×1k, All PN junctions are normal, but they can't work normally after getting on the machine. If you use R×10 or R×1 low-range measurement, you will find that the forward resistance of the PN junction is larger than the normal value. The second and triode can be measured on the road with a pointer multimeter. The more accurate method is: set the multimeter to R×10 or R×1 (usually use R×10, and then use R×1 when it is not obvious). 2. The forward and reverse resistance of the PN junction of the triode, if the forward resistance is not too large (relative to the normal value), and the reverse resistance is large enough (relative to the forward value), it indicates that the PN junction is normal. Otherwise, it is questionable and needs to be welded. Test again after downloading. This is because the peripheral resistance of the diode and triode of the general circuit is mostly over several hundred or several thousand ohms. When measuring with a low resistance value of a multimeter on the road, the influence of the peripheral resistance on the PN junction resistance can be basically ignored.

④Characteristics of IC damage
The internal structure of the integrated circuit is complex, with many functions, and any part of it cannot work normally if it is damaged. There are also two types of damage to integrated circuits: complete damage and poor thermal stability. When it is completely damaged, it can be removed and compared with the normal integrated circuit of the same model to test the forward and reverse resistance of each pin to the ground, and one or several pins can always be found to have abnormal resistance. For poor thermal stability, you can use *** to cool the suspected integrated circuit when the device is working. If the failure time is delayed or the failure no longer occurs, it can be determined. Usually it can only be ruled out by replacing the new integrated circuit.