Color TV Aluminum Electrolytic Capacitors

When repairing a color TV and replacing aluminum electrolytic capacitors, you should use high-quality capacitors and select the correct capacity, especially for capacitors in field and line scanning circuits. For capacitors used as bypass or filtering, a larger capacity error is allowed.

The actual voltage applied to the two ends of the capacitor should be 15%-30% lower than the rated working voltage of the capacitor. It should not be close to, let alone exceed the rated value. Electrolytic capacitors cannot be used in AC circuits due to their polarity, but they can be used in pulse circuits. The polarity of the pulse signal should also be paid attention to.

Domestic capacitors are divided into four groups: T, G, N, and B according to ambient temperature. Groups G and T are suitable for use in cold areas.

Ambient temperature range for capacitor use
---------------|-----------------|-----------------|----------------|-----------------
Group | T | G | N | B
---------------|-----------------|-----------------|-----------------
Ambient temperature for use | -60～+60℃ | -50～+60℃ | -40～+60℃ | -10～+60℃
---------------|-----------------|-----------------|-----------------

From Table 71, we can see that the maximum temperature of the operating environment is +60℃. When the ambient temperature exceeds +60℃, the electrolyte will dry up, causing the capacitor to age and fail prematurely. When replacing components, it is not advisable to place high-power resistors or other heating components close to electrolytic capacitors.

Electrolytic capacitors that have been stored for too long, especially large-capacity capacitors, will have their withstand voltage reduced due to the decomposition of the oxide film. When using them for the first time, you should first apply a low voltage and then gradually increase it to the normal value.

The dielectric leakage of electrolytic capacitors is relatively large. At +20℃, the leakage current of a qualified electrolytic capacitor should not be greater than the value calculated by the following formula.

I=K·C·U·10-4+ｍ

Where, C is the nominal capacitance, in μF; U is the DC working voltage, in V; K is equal to 1 when the ambient temperature is +20°C, and K=3 at +60°C; when the capacitance is less than 5μF, m is 0.2, when it is 5-50μF, m is 0.1, and when the capacitance is greater than 50μF, m=0.

The larger the leakage current, the smaller the insulation resistance, but the leakage current cannot exceed a certain allowable value, otherwise the capacitor will heat up and break down due to excessive leakage current passing through.