How do you know if a capacitor is bad on a circuit board?

There are tens of thousands of small electronic components in the circuit. Therefore, when our circuit design is improper or the voltage is unstable, it is easy to cause circuit failure. Among these circuit failures, chip capacitors are used because of their small size. Due to the characteristics of low withstand voltage, once a fault occurs, it is not easy to find out. Compared with electrolytic capacitors, because of their large size, they are easily deformed due to faults. After a fault occurs, it can be seen with the naked eye whether it is an electrolytic capacitor. caused problems.Today qihe smt pick and place machine sharing how do you know if a capacitor is bad on a circuit board.

So what are the common causes of capacitor failure in the circuit? General capacitor fault phenomenon: capacitor open circuit, breakdown, leakage, breakdown after power on.

Component open circuit

After the capacitor is open circuit, there is no effect of the capacitor. After the capacitor in different circuits has an open circuit fault, the specific fault phenomenon of the circuit is different. For example, there is humming sound after the filter capacitor is opened, and there is no sound after the coupling capacitor is opened.

Component breakdown

After the capacitor breaks down, it loses the function of the capacitor, and there is a path between the two pins of the capacitor, the DC blocking effect of the capacitor disappears, and the DC circuit of the circuit fails, which affects the AC working state.

Component leakage

When the capacitor leaks electricity, the insulation performance between the two plates of the capacitor is reduced, there is a leakage resistance between the two plates, and a DC current flows through the capacitor, the DC blocking performance of the capacitor becomes poor, and the capacity of the capacitor decreases. When the coupling capacitor leaks, it will cause large circuit noise. This is a failure with a relatively high failure rate in small capacitors, and it is difficult to detect the failure.

Breakdown after electrification

The capacitor breaks down after adding the working voltage, and it does not break down after the power is turned off. It does not show the characteristics of breakdown when the multimeter detects it. When the power is turned on, the DC voltage at both ends of the measured capacitor is zero or very low, and the performance of the capacitor deteriorates.

repair method

1. If the internal circuit of the capacitor is open, replace the components; if the external connection of the capacitor is open, re-solder it.
2. The capacitor breaks down, replace it with a new one.
3. The capacitor is leaking, replace it with a new one.
4. Breakdown after power on, replace with new one.

Overhaul of electrolytic capacitors

Electrolytic capacitor is a kind of fixed capacitor. Its fault characteristics have many similarities with those of fixed capacitors. Due to the particularity of electrolytic capacitors, there are many differences in the fault characteristics of electrolytic capacitors. In the circuit, electrolytic capacitors have a high failure rate.

Fault phenomenon: capacitor short circuit

cause of issue

1. No electricity, breakdown, internal short circuit of the capacitor.
2. It is normal when it is not energized, and it breaks down after energizing, and the external connection of the capacitor is short-circuited.

repair method

1. Replace with new components.
2. The external connection of the capacitor is short-circuited, check the short-circuit point, and disconnect it.

Through the repair of capacitor problems above, I believe that everyone will be able to solve the problems in time when they encounter related problems later.

Read more: How do you know if a capacitor is bad on a circuit board?

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