Detailed explanation of the damage and failure of electrolytic capacitors

There are several cases of damage and failure of electrolytic capacitors:

1) The short and open circuit inside the electrolytic capacitor is damaged. The fault phenomenon is the burning switch tube and other current limiting components, such as the current limiting resistor in the safety and switching power supply. Short capacitor, open circuit damage filter capacitors operating in high voltage, high current (such as color TV switching power supply, line output circuit), when the voltage rises for some reason and exceeds its withstand voltage, it breaks down The short circuit is damaged, or the electrolytic capacitor with polarity is equivalent to working in the AC circuit due to the damage of the rectifier diode, and the heat is generated under a large reverse leakage current and the short circuit is damaged. Since the current flowing through the capacitor during the short circuit is large, the capacitor generally bursts or causes the sealing rubber plug to swell. After the filter capacitor is short-circuited, faults such as fuse or current limiting resistor blow, power thick film block or switch tube, and rectifier tube breakdown often occur. The main performance is the "three no" of the whole machine. This kind of fault has commonality in various switching power supplies.

2) Inefficient or slight leakage caused by the decrease of electrolytic capacitor capacity, the fault phenomenon is the "S"-shaped distortion or line-synchronization phenomenon of TV image. For the current TV with IIC bus, some special failure phenomena appear, if The critical state of the sync card, the accompanying sound may affect the quality of the TV, so that the companion chapter appears at any time. The main reason is that the parameters of the capacitor change, but it does not completely fail. It still has a certain effect, but it does not achieve the proper function, so that the existing fault phenomenon appears. And such faults are not easy to judge and eliminate.

3) The failure caused by the disappearance of the capacity of the electrolytic capacitor, complete leakage or explosion is the most difficult to identify and repair after the capacitor in the power supply fails. Because the capacitor is measured, everything is tested with a multimeter, but after the capacitor is mounted on the circuit. The capacity of the capacitor disappears completely. This is one of the most difficult soft faults in the circuit. That is, the component cannot withstand the voltage. When there is voltage, it is easy to disappear completely.