Phenomenon of damage to commonly used electronic components

There are also differences in physical strength in circuits, and the ranking of electronic components' resistance ability is as follows:

Resistors, inductors, capacitors, and semiconductor devices (including diodes, transistors, field transistors, and integrated circuits) have the highest probability of damage under the same working conditions.

So when we search for faulty components, we should prioritize checking diodes, transistors, field transistors, integrated circuits, etc. Generally, breakdown is more common when semiconductor devices are damaged. When using a multimeter diode buzzer to test any two pins of these devices, the lowest resistance of a PN junction should be around 500. If the buzzer sounds, it is likely that the device is damaged. It can be removed and retested to confirm.

In circuits, components operating under high voltage, high current, and high power conditions undoubtedly bear high pressure and have a high possibility of damage. They are also critical and functional components of the circuit.

Wherever there is a high current, heat is generated (Joule Lenz's law - heat is proportional to the square of the current), so any component with a heat sink is a vulnerable part. High power resistors are also vulnerable components. How can high-power resistors be identified? It has nothing to do with its resistance, only with its volume. The larger the volume, the greater the power. In a circuit, fuses and fuse resistors are the least secure components. Firstly, because of its low melting point, it is easy to break, and secondly, because it is a way to protect others' risks and rush to the front line as a security guard, it breaks first when it breaks.

The ways in which components are damaged include overvoltage damage, overcurrent damage, and of course, mechanical damage. Overvoltage damage, such as lightning strikes, can cause breakdown of bridge rectifier diodes. Overcurrent damage such as thermal breakdown of display diodes.

The appearance of the component damaged by overvoltage does not show significant changes, only the parameters have changed completely. The surface temperature of components damaged by overcurrent is very high, with obvious changes such as cracks, discoloration, and small pits. In severe cases, the circuit boards around the components may turn yellow or black.

When commonly used electronic components appear normal on the outside, a digital multimeter can be used for some simple tests.

resistance

This is very simple, test the resistance to see if it's correct.

diode

Using a digital multimeter to test the voltage drop of the PN junction can be compared with intact diodes of the same model.

transistor

Whether it is an N diode or a P diode, a digital multimeter can be used to measure and test whether the two PN junctions are normal.

Field-effect transistor

Test whether the PN junction of the internal diode of the field-effect transistor is normal, and test whether there is a short circuit in GD and GS.

capacitance

Non polarized capacitor, breakdown short circuit or desoldering, severe leakage or resistance effect.

The effective characteristics of electrolytic capacitors are: breakdown short circuit, increased leakage, decreased capacity or open circuit.

inductance

The effective characteristics are: wire breakage and desoldering.

chip

The internal structure of integrated circuits is complex and has many functions, and any part that is damaged cannot function 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 compared with a normal integrated circuit of the same model to measure the positive and negative resistance of each pin to ground. One or several pins with abnormal resistance values can always be found. For those with poor thermal stability, the suspected integrated circuit can be cooled with anhydrous alcohol during equipment operation. If the fault occurs later or no longer occurs, it can be determined. Usually, only a new integrated circuit can be replaced to eliminate it.

Whether it is a fault caused by natural wear and tear or a fault caused by human damage, it can generally be attributed to three types of faults: circuit contact open circuit, electronic component damage, and software failure. If the contact is open, it is generally easier to repair if the wire is broken, the plug is disconnected, or there is poor contact. The damage to electronic components (except for obvious burning and heating) is generally difficult to detect by observers. In many cases, instruments are necessary for detection and judgment. Therefore, for technicians, it is essential to first understand the practical characteristics of various devices, which is crucial for troubleshooting circuit faults and improving maintenance efficiency.