Possible factors for component damage

What are electronic components? What are the factors that may cause them to be damaged? In fact, the basic units of electronic circuits are electronic components. These devices exist in the form of hardware, and they have their own electrical parameters, such as voltage, current, and power. Features etc.

Therefore, components are the most vulnerable items, but their failures are regular. General faults are manifested in two categories: electrical parameter damage and physical damage. The damage to electrical parameters also includes damage caused by voltage and current exceeding the rated value. Physical damage includes fractures, deformations, changes in resistance parameters, etc.

1. Characteristics of resistor damage

Resistors are the most numerous components in electrical equipment, but they are not the components with the highest damage rate. The most common type of resistor damage is an open circuit. It is less common for the resistance value to increase, and it is very rare for the resistance value to decrease. Common ones include carbon film resistors, metal film resistors, wirewound resistors and fuse resistors.

The first two types of resistors are the most widely used, and their damage characteristics are: First, low resistance values ​​(below 100Ω) and high resistance values ​​(above 100kΩ) have higher damage rates, and intermediate resistance values ​​(such as several hundred ohms to tens of kiloohms) There is very little damage; secondly, when low-resistance resistors are damaged, they are often burnt and blackened, which is easy to find, while when high-resistance resistors are damaged, there are few traces.

Wirewound resistors are generally used for large current limiting, and their resistance is not large. When cylindrical wire-wound resistors are burned out, some will turn black or have skin or cracks on the surface, while others will have no traces. Cement resistors are a type of wirewound resistor and may break when burned out, otherwise there will be no visible traces. When the fuse burns out, some parts of the surface will explode, and some may leave no trace, but they will never be burnt or blackened. Based on the above characteristics, you can focus on checking the resistor and quickly find the damaged resistor.

2. Characteristics of electrolytic capacitor damage

Electrolytic capacitors are widely used in electrical equipment and have a high failure rate. Damage to electrolytic capacitors has the following symptoms:

1. The capacity is completely lost or the capacity becomes smaller;

2. It is a slight or serious leakage;

3. The capacity is lost or the capacity becomes smaller and there is leakage.

Methods to find damaged electrolytic capacitors include:

(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 surface of the capacitor. This kind of capacitor must not be used again; some capacitors will bulge after being damaged, and this kind of capacitor cannot continue to use;

(2) Touch: Some electrolytic capacitors with serious leakage will heat up after turning on the machine, and may even be hot when touched with fingers. Such capacitors must be replaced;

(3) There is electrolyte inside the electrolytic capacitor. Long-term baking will dry out the electrolyte and reduce the capacitance. Therefore, it is necessary to focus on checking the capacitor near the heat sink and high-power components. The closer it is, the more likely it is to be damaged. The greater the sex.

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

Damage to transistors is generally caused by PN junction breakdown or open circuit, among which breakdown short circuit is the most common.

In addition, there are two types of damage manifestations:

One is that the thermal stability deteriorates, which is normal when starting up, but soft breakdown occurs after working for a period of time; the other is that the characteristics of the PN junction deteriorate. When measured with a multimeter R×1k, each PN junction is normal, but the upper The machine cannot work normally. If you use R×10 or R×1 low-range measurement, you will find that the forward resistance of the PN junction is larger than the normal value.

To measure the second and third transistors, you can use a pointer multimeter to measure them on the road. The more accurate method is:

Set the multimeter to the R×10 or R×1 scale (generally use the R×10 scale, and then use the R×1 scale when it is not obvious) and measure the forward and reverse resistance of the PN junction of the second and third transistors on the road. If the forward resistance is not too large, If the resistance is large (relative to the normal value) and the reverse resistance is large enough (relative to the forward value), it indicates that the PN junction is normal. Otherwise, it is doubtful and needs to be soldered and then measured again. This is because the peripheral resistance of diode and transistor in general circuits is mostly hundreds or thousands of ohms or more. When measured on the road with a multimeter at the low resistance range, the influence of the peripheral resistance on the PN junction resistance can be basically ignored.

4. Characteristics of integrated circuit damage

The internal structure of an integrated circuit is complex and has many functions. If any part is damaged, it will not work properly. There are also two types of damage to integrated circuits: complete damage and poor thermal stability. When it is completely damaged, you can dismantle it and compare the forward and reverse resistance of each pin to ground with a normal integrated circuit of the same model. You can always find one or several pins with abnormal resistance.

For those with poor thermal stability, you can use absolute alcohol to cool the suspected integrated circuit while the equipment is working. If the fault occurs later or the fault no longer occurs, it can be determined. Usually it can only be eliminated by replacing a new integrated circuit. The above factors that may lead to rapid damage to electronic components, I hope it can help you.