What are the symptoms of electronic component damage? Analysis of fault characteristics

Although there are a large number of electronic components in electrical equipment, their faults are regular. What is the damage performance of electronic components in daily work? Next, let's take a look at the analysis of fault characteristics.

1. Characteristics of resistance damage

Resistance is the most numerous component in electrical equipment, but it is not the component with the highest failure rate. Resistance damage is the most common approach, with increased resistance being relatively rare and decreased resistance being very rare. Common types include carbon film resistors, metal film resistors, wire wound resistors, and fuse resistors. The first two types of resistors are most widely used, and their damage characteristics are that the damage rate of low resistance values (below 100 Ω is high resistance value (above 100k Ω)) is very high, and the damage rate of intermediate resistance values (such as hundreds of euros to tens of thousands of euros) is rarely; Secondly, when low resistance resistors are damaged, they usually burn out and become black, which is easy to detect, while when high resistance resistors are damaged, there are few traces. Wire wound resistors are generally used for high current limiting and have low resistance values. When a cylindrical wire wound resistor burns, it will turn black or the surface skin will burst, some without any marks. Cement resistor is a type of wire wound resistor that may rupture when burned, otherwise there will be no visible traces. When the fuse resistor burns, a piece of skin will explode on the surface, some without any traces, but it will never burn and turn black. Based on the above characteristics, when checking the resistance, one can focus their attention and quickly find the damaged resistance.

2. Features of Electrolytic capacitor damage

Electrolytic capacitor consumes a lot in electrical equipment and has a high failure rate. The Electrolytic capacitor is damaged in the following ways: first, it is completely lost in volume or reduced in capacity; The second is mild or severe leakage; The third is volume loss or capacity reduction. The search for damaged Electrolytic capacitor includes:

(1) Look: Some capacitors may leak when damaged, and there is a layer of oil on the surface of the circuit board or even the capacitor surface below the capacitor, which cannot be used anymore; Some capacitors expand after damage and cannot be used anymore;

(2) Touch: After restart, some Electrolytic capacitor with serious power failure will be scalded, or even scalded when touched by hand. Such capacitors must be replaced;

(3) There is electrolyte in the Electrolytic capacitor. Long term baking can dry the electrolyte and reduce its capacity. Therefore, it is important to focus on checking the capacitors near the heat sink and high-power components. The closer you are to it, the greater the likelihood of damage.

3. Characteristics of damage to semiconductor devices such as diodes and transistors

2、 The damage of the transistor is generally caused by PN junction penetration or conduction, especially through short circuits. In addition, there are two destructive manifestations: one is a decrease in thermal stability, which is reflected in normal startup and soft breakdown after working for a period of time; Another way is to reduce the characteristics of PN junctions, using a multimeter R × 1k test, if RN is used, the PN junction is normal, but it cannot operate normally after being installed on the computer × 10 or R × In low range measurements, it can be found that the positive resistance value of the PN junction is greater than the standard value. Measure the diode and transistor on the road using a pointer multimeter. A more accurate method is to place the multimeter R × 10 or R × First gear (generally used for R × 10 gears, use R when not obvious × 1) If the positive resistance is not too large (relative to the standard value) and the reverse resistance is large enough (relative to the positive value), it indicates that the PN junction is normal. On the contrary, it is questionable and needs to be measured after welding. This is because the peripheral resistance of the diodes and transistors in general power supplies is mostly over a few hundred euros. When measuring on the road with a multimeter at a low resistance range, the influence of peripheral resistance on the PN junction resistance can be basically ignored.

4. Characteristics of integrated circuit damage

The internal structure of integrated circuits is complex, with various functions, and any damaged part cannot function properly. There are two other types of damage to integrated circuits: complete damage and poor thermal stability. When completely damaged, it can be removed. Compared with normal integrated circuits of the same model, it is possible to detect the forward and reverse resistance of each pin to ground, and always detect abnormal resistance in one or more of the pins. For integrated circuits with poor thermal stability, if the fault occurs with a delayed time or no longer occurs, anhydrous ethanol can be used for cooling during equipment operation. In general, integrated circuits can only be replaced to clear.

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

Resistance detection is simple, isn't it?

The voltage drop of the diode PN junction is detected using a digital multimeter and can be compared with complete diodes of the same model.

Whether the triode is N tube or P tube, you can use a data multimeter to measure whether the two PN junctions are normal.

Field-effect transistor detects whether the PN junction of the diode in the Field-effect transistor body is normal, and whether GD and GS are short circuited.

Capacitor without electrodes, with penetration short circuit and open welding, severe electrical discharge or resistance effect.

The effective characteristics of Electrolytic capacitor are: penetrating short circuit, increasing electrification, reducing volume or short circuit.

The characteristics of inductance results are as follows: disconnection, disconnection, and disconnection

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