Life is dead, and electronic components have a life. The life of an electronic component is not only related to its structure and properties, but also closely related to its use environment and its role in the circuit.
When winter is approaching, a cold current is coming, and some of them are physically weak. They cannot bear the changes in the environment, and they have a cold. However, people who are physically strong have a strong ability to resist and are not sick. This shows that illness is related to your own constitution.
There are also physical strengths in the circuit. The resistance ranking of electronic components is as follows:
Resistors, inductors, capacitors, and semiconductor devices (including diodes, transistors, field transistors, and integrated circuits), that is, under the same operating conditions, the probability of semiconductor device damage is greatest.
Therefore, when we look for faulty components, we must first check diodes, transistors, field transistors, integrated circuits, etc. Generally, breakdown is common when semiconductor devices are damaged. Multimeter diode buzzer files should have a minimum of PN on any two feet of these devices. The resistance value of the knot is about 500. If the buzzer is 80% broken, you can remove it and test to confirm.
We all know that the bitch in his early years rots first, and the chief's guards must be prepared to sacrifice at any time, which shows that the job determines the degree of danger.
In the circuit, the components that work under high voltage, high current, and high power state are undoubtedly under great pressure and have a high possibility of damage. At the same time, they are also key components and functional components of the circuit.
Wherever there is a high current, the heat is large (Joule's law-heat is proportional to the square of the current), so all components with heat sinks are wearing parts. High-power resistors are also wearing parts. How can a high-power resistor be seen? It has nothing to do with its resistance, but only with its volume. The larger the volume, the greater the power. In the circuit, fuses and fuses are the most unsafe components. First of all, because of its low melting point, it is easy to break, and because it is the insurance of others, it rushes to the front line and acts as a guard.
Component damage can be caused by overvoltage damage, overcurrent damage, and of course mechanical damage. Overvoltage damage such as lightning strikes, breakdown of bridge rectifiers. Overcurrent damage such as thermal breakdown of the monitor tube.
There are various ways of death for humans. Overpressure damage, such as decapitation, the head fell off, the person was dead, and his body was intact. There is no obvious change in the appearance of the component damaged by overvoltage, but the parameters have all changed. Overcurrents are like beatings to death. They can still be forbidden at first, but they are getting worse and worse. By the time they die, they are all scaly and fuzzy. The surface temperature of the components damaged by overcurrent is very high, and there are obvious changes such as cracks, discoloration and small pits. In severe cases, the circuit board around the component turns yellow and black.
When the appearance of common electronic components looks normal, you can use the digital multimeter to do some simple tests.
resistance
This is very simple, the test resistance is correct.
diode
Using a digital multimeter to test the voltage drop of the PN junction can be compared with a good diode of the same type.
Triode
Whether it is N tube or P tube, you can use digital multimeter to measure and test whether the two PN junctions are normal.
FET
Test whether the PN junction of the body diode of the field effect tube is normal, and test whether there is a short circuit in GD, GS.
capacitance
Non-polar capacitor, short-circuit breakdown or desoldering, serious leakage or resistance effect.
The practical characteristics of electrolytic capacitors are: short circuit breakdown, increased leakage, reduced capacity or open circuit.
inductance
Effectiveness characteristics: disconnection, desoldering
chip
The internal structure of the integrated circuit is complex, and there are many functions, and any part of the integrated circuit cannot work properly. There are also two types of integrated circuit damage: complete damage and poor thermal stability. When it is completely damaged, you can remove it and compare the forward and reverse resistance of each pin to ground with a normal integrated circuit of the same type. You can always find that the resistance of one or more of the pins is abnormal. For devices with poor thermal stability, the suspected integrated circuit can be cooled with anhydrous alcohol during the operation of the equipment. If the time of failure is delayed or no longer occurs, it can be determined. It can usually only be replaced by a new integrated circuit.
Whether it is a fault caused by natural loss or a fault caused by human damage, it can generally be attributed to three types of faults: open circuit contacts, damaged electronic components and software faults. The contact is open. If it is a broken wire, disconnected plug, poor contact, etc., it is generally easier to repair. The damage of electronic components (except for obvious burnout and heat) is generally difficult for observers to find. In many cases, instruments must be used to detect and judge. Therefore, for technicians, it is necessary to understand various devices. The characteristics of actual effects are extremely important for troubleshooting circuit faults and improving maintenance efficiency.
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