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Fault characteristics of electronic components
Release time:
2020-05-25
Although the number of electronic components inside the electrical equipment, but its failure is a rule to follow.
Although the number of electronic components inside the electrical equipment, but its failure is a rule to follow.
1. Characteristics of resistance damage
Resistance is a large number of components in electrical equipment, but it is not a component with high damage rate. Resistance damage to the open circuit is common, the resistance value becomes more rare, the resistance value becomes smaller is very rare. There are carbon film resistors, metal film resistors, wire wound resistors and insurance resistors. The first two kinds of resistors are widely used, and their damage is characterized by high damage rate of low resistance value (below 100Ω) and high resistance value (100kΩ), and little damage of resistance value (such as hundreds of ohms to tens of thousands of ohms); Second, when low-resistance resistors are damaged, they are often scorched and blackened, which is easy to find, while when high-resistance resistors are damaged, there are few traces. The wire wound resistor is used for large current limiting, and the resistance value is not large. When the cylindrical wire-wound resistor burns out, some will turn black or the surface will explode and crack, and some will have no trace. Cement resistance is a kind of wire wound resistance, it will break when burned out, otherwise there is no visible trace. When the safety resistor burns out, some of the surface will blow up a piece of skin, and some have no traces, but they will never burn black. According to the characteristics, when checking the resistance, you can focus on quickly find out the damaged resistance.
2. Characteristics of electrolytic capacitor damage
Electrolytic capacitors are used in a large amount of electrical equipment and have a high failure rate. Electrolytic capacitor damage has the following performance:
One is the loss of capacity or capacity becomes smaller;
Two is a slight or serious leakage;
Three is the loss of capacity or capacity becomes smaller and leakage.
Methods to find damaged electrolytic capacitors are:
(1) Look: Some capacitors will leak when damaged, and there will be a layer of oil stains on the surface of the circuit board under the capacitor and even on the outside of the capacitor. This capacitor can never be used again; Some capacitors will bulge after damage, and this capacitor cannot be used any more. Therefore, when selecting capacitors in the early stage, we should control the quality and try to choose brand capacitors, such as the capacitor giant-Guoju Capacitor.
(2) Touch: After starting up, some electrolytic capacitors with serious leakage will heat up, and even hot hands when touched with fingers. This capacitor is replaced;
(3) electrolytic capacitor internal electrolyte, long time baking will make the electrolyte dry, resulting in reduced capacitance, to focus on checking the heat sink and high-power components near the capacitor, the closer to it, the greater the possibility of damage.
3. Semiconductor device damage characteristics
The damage of the 2. transistor is the PN junction breakdown or open circuit, in which the majority of the breakdown short circuit. In addition, there are two kinds of damage: one is the deterioration of thermal stability, which is normal when starting up and soft breakdown occurs after working for a period of time; The other is that the characteristics of PN junction deteriorate. When measured with a multimeter R× 1k, all PN junctions are normal, but they cannot work normally after being put on the machine. When measured with R× 10 or R× 1 low range gear, it will be found that the positive resistance of PN junction is larger than normal. The 2. triode 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 gear (use R× 10 gear and R× 1 gear when it is not obvious) to measure the positive and negative resistances of the PN junction of the 2. triode on the road. The positive resistance is not too large (normal value), and the negative resistance is large enough (positive value) to indicate that the PN junction is normal, on the contrary, it is doubtful and needs to be tested after welding. This is the 2. of the circuit. The peripheral resistance of the triode is mostly in the hundreds or thousands of ohms. The influence of the peripheral resistance on the PN junction resistance can be basically ignored when measured on the road with a multimeter with low resistance.
4. Characteristics of integrated circuit damage
The internal structure, function, and part of the integrated circuit are damaged and cannot work normally. 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 type to measure the positive and negative resistance of each pin to ground, and one or several pins can always be found with abnormal resistance. For those with poor thermal stability, it can be determined that the suspected integrated circuit can be cooled with anhydrous alcohol when the equipment is working, and the fault occurrence time is delayed or no longer occurs. Usually can only be replaced with a new integrated circuit to exclude.
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