Electronic components are used in various fields, so damage is also very common. Resistance, inductance, capacitance, semiconductor devices (including diodes, triodes, field tubes, and integrated circuits), that is to say, under the same working conditions, semiconductor devices have a high probability of damage.
Therefore, when looking for faulty components, we must first check diodes, triodes, field tubes, integrated circuits, etc. Generally, breakdown is more common when semiconductor devices are damaged. Any two pins of these devices should also have a minimum of PN when the multimeter diode buzzer test. The resistance value of the junction is about 500. If the buzzer is 80% broken, it can be removed and tested to confirm.
We all know that the rafters in their early days rot first, and the long guards must be prepared, which shows that the job position determines the degree of danger.
In the circuit, components that work under high voltage, high current, and high power are undoubtedly subjected to greater pressure and the possibility of damage is high, and they are also key components and functional components of the circuit.
Wherever there is a large current, the heat is large (Joule Lenz's law-heat is proportional to the square of the current), so all components with heat sinks are vulnerable parts. High-power resistors are also vulnerable parts. How can high-power resistors be seen? It has nothing to do with its resistance, only its volume. The larger the volume, the greater the power. In the circuit, fuses and fuse resistors are uninsured components. First, because of their low melting point, they are easy to break, and because they are a risk to protect others, they rush to the front line. When they are a guard, they break first.
The ways of component damage include overvoltage damage, overcurrent damage, and of course mechanical damage. Overvoltage damage such as lightning strikes, breakdown of bridge rectifiers. Over-current damage such as thermal breakdown of the display tube.
Corresponding to people, there are also ways to die. There is no visible change in the appearance of components damaged by overvoltage, but the parameters have all changed. Excessive flow is like being beaten to death. At first, it can be tolerated, but it is getting worse and worse. When he dies, he is covered with bruises and blood. The surface temperature of components damaged by overcurrent is very high, and there are changes such as cracks, discoloration, and small pits. In severe cases, the circuit board around the component turns yellow or black.
Commonly used electronic components can be used to do some simple tests when they appear to be normal in appearance.
Resistance: Is the test resistance correct?
Common phenomena that occur after damage to electronic components
Diode: Use a digital multimeter to test the voltage drop of the PN junction, which can be compared with a good diode of the same model.
Triode: Whether it is N tube or P tube, you can use a digital multimeter to test whether the two PN junctions are normal.
Field effect tube: test whether the PN junction of the body diode of the field effect tube is normal, and whether there is a short circuit in GD and GS.
Capacitance: Non-polar capacitor, short-circuit breakdown or desoldering, serious leakage or resistance effect.
The practical characteristics of electrolytic capacitors are: breakdown and short-circuit, increased leakage, reduced capacity or open circuit.
The effective characteristics of the inductor are: disconnection and desoldering.
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