Although the number of electronic components within the electrical equipment, but its failure is regular.
1. Characteristics of resistance damage
Resistance is a large number of components in electrical equipment, but not a high damage rate components. Resistor damage to the open circuit is common, the resistance value becomes large less common, the resistance value becomes small very rare. Resistors are carbon film resistors, metal film resistors, wirewound resistors and safety resistors. The first two types of resistors are widely used, the damage is characterized by a low resistance (100Ω or less) and high resistance (100kΩ) of the damage rate is higher, the resistance (such as hundreds of ohms to dozens of kilo-ohms) of the damage is very rare;
Secondly, low resistance value resistor damage is often burnt black, it is easy to find, while the high resistance value resistor damage rarely traces. Wirewound resistors are used as current limiting for high currents and do not have a large resistance value. Cylindrical wirewound resistors are burnt black or the surface will burst skin, cracks, some have no trace. Cement resistor is a kind of wirewound resistor, it will break when burned out, otherwise there is no visible trace. Insurance resistor burned out when some of the surface will blow off a piece of skin, some also have no trace, but never burnt black. According to the characteristics, in the inspection of the resistance can be focused on, quickly find the damaged resistor.
2. Electrolytic capacitor damage characteristics
Electrolytic capacitors are used in a large amount of electrical equipment, the failure rate is very high. Electrolytic capacitor damage has the following manifestations:
First, the loss of capacity or capacity becomes small;
Second, slight or serious leakage;
Third, the loss of capacity or capacity becomes small with leakage.
Find damaged electrolytic capacitors methods are:
(1) look: some capacitors will leak when damaged, capacitance below the surface of the circuit board and even capacitance appearance will have a layer of oil stains, this capacitor can not be used again; some capacitors will bulge after the damage, this capacitor can not continue to use; therefore, in the early selection of capacitors, you should be put on the quality of the quality of the gate, try to choose a well-known brand of capacitors, such as capacitance giants --- National Giant capacitors. -National Giant capacitors.
(2) Touch: some serious leakage of electrolytic capacitors after power on will be hot, touch with a finger will even be hot, this capacitor replacement;
(3) electrolytic capacitors have electrolyte inside, long time baking will make the electrolyte dry, resulting in reduced capacitance, to focus on checking the heat sink and high-power components near the capacitor, the closer it is, the greater the possibility of damage.
3. Semiconductor device damage characteristics
Diode, triode damage is the PN junction breakdown or open circuit, which is mostly short-circuit breakdown. In addition, there are two kinds of damage performance: one is the thermal stability deterioration, manifested as normal at power-on, after working for a period of time, soft breakdown occurs; the other is the PN junction characteristics of the deterioration of the PN junction, with the multimeter R × 1k measurement, the PN junction are normal, but after the machine can not work properly, with R × 10 or R × 1 low range gear measurement, it will be found that the PN junction forward resistance is larger than the normal value.
Measurement of diodes, transistors can be measured with a pointer multimeter in the road, the more accurate method is: the multimeter will be set to R × 10 or R × 1 file (with R × 10 file, when it is not obvious, and then use the R × 1 file) in the road to measure the diode, transistor PN junction forward and reverse resistance, forward resistance is not too large (normal value), reverse resistance is large enough (forward value), indicating that the PN junction is normal, and vice versa, it is worthwhile to doubt, need to be welded down and then measured.This is the circuit of the diode, transistor peripheral resistance is mostly in the hundreds, thousands of ohms, with a multimeter low resistance file in the road measurement, you can basically ignore the peripheral resistance on the PN junction resistance.
Cement resistor is a kind of wirewound resistor, it will break when burned out, otherwise there is no visible trace.
Insurance resistor burned out when some of the surface will blow off a piece of skin, some also have no trace, but never burnt black.According to the characteristics, in the inspection of the resistance can be focused on, quickly find the damaged resistor. 2. Electrolytic capacitor damage characteristics Electrolytic capacitors are used in a large amount of electrical equipment, the failure rate is very high.Electrolytic capacitor damage has the following manifestations:This is the circuit of the diode, transistor peripheral resistance is mostly in the hundreds, thousands of ohms, with a multimeter low resistance gear in the road measurement, you can basically ignore the peripheral resistance on the PN junction resistance.
4. Characteristics of integrated circuit damage
Integrated circuit internal structure, function, part of the damage can not work properly. There are also two kinds of integrated circuit damage: complete damage, poor thermal stability. Completely damaged, it can be removed, and the normal integrated circuits of the same type compared to the measurement of each of its pins on the ground, positive and negative resistance, can always find one or several pins abnormal resistance. Poor thermal stability, you can use anhydrous alcohol to cool the suspected integrated circuits when the equipment is working, the failure time delayed or no longer occurring failures, judgment. Usually can only be ruled out by replacing the integrated circuit with a new one.