Circuit board capacitance fault maintenance

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Capacitance failure is the most common fault in electronic equipment. Capacitance damage is often accompanied by leakage, short circuit, capacity reduction, complete loss of capacity and other manifestations.


Capacitance plays different roles in the circuit and causes different faults. In the industrial control circuit board, the digital circuit accounts for the vast majority, the capacitance is mostly used as power filter, the capacitance is less used as signal coupling and oscillating circuit. If the electrolytic capacitance used in the switching power supply is damaged, the switching power supply may not vibrate and has no voltage output. If the capacitance is between the positive and negative power supply of the digital circuit, the fault performance is the same as above.

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If the capacitance is taken down to measure the capacity, it is found to be much lower than the actual value. The life of capacitor is directly related to the ambient temperature. The higher the ambient temperature, the shorter the life of capacitor. This rule applies not only to electrolytic capacitance, but also to other capacitors. Therefore, when looking for fault capacitance, it is important to check the capacitance close to the heat source, such as the capacitance near the radiator side and high-power components.

Some capacitors have severe leakage and may even become hot when touched by fingers. The capacitors must be replaced. The fault caused by capacitance damage is generally the most part of the fault, which eliminates the possibility of bad contact during maintenance.

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