Five things to note when replacing capacitors

The common fault phenomena of fixed capacitors are leakage, short circuit, open circuit, poor contact of the internal leads of the capacitor (the connection between the pole piece and the lead), etc. Especially electrolytic capacitors, their failure rate is much higher than other types of capacitors. Common fault phenomena of electrolytic capacitors include leakage, capacity reduction, breakdown, electrolyte leakage, etc. After the capacitor is damaged, the original model should be used. However, there are many types of capacitors. If the same model is not available, a substitute should be made. The precautions for substitution are as follows:

1. The nominal value of the substitute capacitor can fluctuate by ±10% based on the nominal value of the original capacitor. For power supply filter capacitors, bypass capacitors, etc., the floating range can be larger, but for some circuit capacitors The original nominal value must be used when replacing, otherwise the circuit will not work properly. For example, the capacitors of the resonant circuit and time constant circuit must be replaced according to the original nominal value. Another example is the coupling capacitor between the TV's amplifier and the cathode of the picture tube. After the capacitor is damaged, it must be replaced according to the original nominal value, otherwise the image quality will be affected.

2. The rated voltage of the substitute capacitor must be greater than or equal to the rated voltage of the original capacitor, or greater than the working voltage of the actual circuit.

3. The frequency characteristics of the substitute capacitor must meet the frequency requirements of the actual circuit, or a capacitor with high frequency characteristics must be used to replace a capacitor with low frequency characteristics.

4. Mica capacitors and porcelain capacitors can replace paper capacitors. Porcelain capacitors can replace mica capacitors and glass glaze capacitors. Tantalum electrolytic capacitors can replace aluminum electrolytic capacitors.

5. When there is no suitable capacitor replacement, the series or parallel connection of capacitors can be used to obtain the appropriate capacitance. If the withstand voltage value of the capacitor is not enough, you can also use series connection to increase the withstand voltage value. If the circuit requires a withstand voltage of more than 25V, a capacitor with a capacitance of 500uf. There are only 1000uf/16V capacitors, two 1000uf/16V capacitors can be connected in series. After being connected in series, an equivalent capacitor with a withstand voltage of 32V and a capacitance of 500uf can be obtained.