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1. Power adapter resistance damage characteristics
Resistance is the most abundant component in electrical equipment, but it is not the component with the highest damage rate. If the resistance is damaged, the resistance is increased, and the resistance is smaller. It is rare that the resistance is small. There are several kinds of carbon film resistors, metal film resistors, wirewound resistors and fuse resistors. The first two resistors are the most widely used, and their damage characteristics are low resistance (less than 100Ω) and high resistance (100kΩ). The damage rate is very low, such as few hundred ohms to several tens of kilo ohms. Damage; second, the low resistance value of the resistor is often burnt black, it is found, and the high resistance resistance is rarely damaged. Wirewound resistors are used for high current limiting and have low resistance. When the cylindrical wirewound resistor is burnt out, some may be black or have a surface blast, crack, and some have no trace. Cement resistance is a kind of wirewound resistor that breaks when burned out, otherwise there is no visible trace. When the fuse is burned out, some surfaces will blow up a piece of skin, and some will have no trace, but it will never burnt and black. Depending on the characteristics, you can focus on checking the resistance and quickly find the damaged resistor.
2. Power adapter electrolytic capacitor damage characteristics
Electrolytic capacitors are used in large quantities in electrical equipment and have a high failure rate. Electrolytic capacitor damage has the following performances: first, loss of capacity or capacity becomes smaller; second, slight or severe leakage; third, loss of capacity or capacity, and leakage. The methods for finding damaged electrolytic capacitors are:
(1) Look: Some capacitors will leak when they are damaged. There will be a layer of oil on the surface of the circuit board under the capacitor or even the surface of the capacitor. This capacitor can never be used again. Some capacitors will be damaged.
(2) Touch: Some electrolytic capacitors with serious leakage will heat up after starting up, and even hot when touched with fingers, this capacitor is replaced;
(3) There is electrolyte inside the electrolytic capacitor. If it is baked for a long time, the electrolyte will dry out, resulting in a decrease in capacitance. It is important to check the capacitance near the heat sink and high-power components. The closer to it, the more damage The bigger.
3. Features of semiconductor device damage such as power adapter pole tube
Second, the damage of the triode is the PN junction breakdown or open circuit, in which the breakdown short circuit is mostly. In addition, there are two kinds of damage performances: one is that the thermal stability is worse, the performance is normal at booting, after a period of work, soft breakdown occurs; the other is that the characteristics of the PN junction are deteriorated, measured by a multimeter R×1k, Each PN junction is normal, but it can not work normally after being put on the machine. When measured with R×10 or R×1 low-range, it will find that the positive resistance of its PN junction is larger than the normal value. Measuring the second and third transistors can be measured on the road with a pointer multimeter. The more accurate method is to set the multimeter to R×10 or R×1 (using R×10 files, and then using R×1 files when not obvious). , PN junction positive and negative resistance of the triode, the forward resistance is not too large (normal value), the reverse resistance is large enough (positive value), indicating that the PN junction is normal, and vice versa, it is doubtful, it needs to be measured after welding . This is that the external resistance of the second and third transistors of the circuit is mostly in the hundreds and thousands of ohms. It is measured by the low resistance value of the multimeter, and the influence of the peripheral resistance on the PN junction resistance can be basically ignored.
4. Power adapter integrated circuit damage features
The internal structure, function, and part of the damage of the integrated circuit are not working properly. 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 the positive and negative resistance of each pin to ground can be measured compared with the normal integrated circuit. It is always found that one or several of the pins have abnormal resistance. For poor thermal stability, the suspected integrated circuit can be cooled with anhydrous alcohol while the equipment is in operation, and the time of occurrence of the fault is delayed or no longer occurs, and the determination is made. Usually only new integrated circuits can be replaced to eliminate them.