Five major considerations for replacing capacitors

The fault phenomenon that is easy to occur with fixed capacitors is leakage, short circuit, open circuit, poor internal lead contact of the capacitor (where the pole piece is connected to the lead). In particular, electrolytic capacitors have a much higher failure rate than other types of capacitors. Common faults in electrolytic capacitors include leakage, reduced capacity, breakdown, and electrolyte leakage. The original model should be used after the capacitor is damaged. However, there are many types of capacitors. If there are no different models, they should be replaced. The precautions for substitution are as follows:

The nominal value of the capacitor can be ±10% floating on the basis of the nominal value of the original capacitor. For the power supply filter capacitor, bypass capacitor, etc., the floating range can be larger, but the capacitance of some circuits is replaced. The time must be changed according to the original nominal value, otherwise it will cause the circuit to work abnormally. For example, the capacitance of the resonant circuit and the time constant circuit must be replaced by the original nominal value. Another example is the coupling capacitance of the TV set and the cathode of the picture tube. After the capacitor is damaged, it must be replaced by the original nominal value, otherwise the image quality will be affected.

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 operating voltage of the actual circuit.

The frequency characteristics of the surrogate capacitor must meet the frequency requirements of the actual circuit, or replace the capacitor with the low frequency characteristic with a capacitor with a high frequency characteristic.

Mica capacitors and ceramic capacitors can be substituted for paper capacitors. Ceramic dielectric capacitors can be substituted for mica capacitors and glass glaze capacitors. Tantalum electrolytic capacitors can replace aluminum electrolytic capacitors.

When there is no suitable capacitor replacement, the capacitor can be used in series or in parallel to obtain a suitable capacitance. If the withstand voltage of the capacitor is not enough, the series voltage can also be used to increase the withstand voltage. For example, if the circuit requires a capacitor with a withstand voltage of 25V or more and a capacitance of 500uf. Only 1000uf/16V capacitors can be used to connect two 1000uf/16V capacitors in series. After connecting in series, an equivalent capacitor with a withstand voltage of 32 V and a capacitance of 500 uf can be obtained.