​Capacitors play an important role in tuning, bypass, coupling and filtering circuits. Transistor radio tuning circuit to use it, color TV coupling circuit, bypass circuit also need to use it. What are the detection methods for fixed capacitors?

1. Detection of small capacitance below 10PF: because the capacity of fixed capacitor below 10PF is too small, it can only qualitatively check whether there is leakage, internal short circuit or breakdown phenomenon when measuring with a multimeter. When measuring, the multimeter R can be selected × For 10K gear, connect two pins of the capacitor with two probes, and the resistance value should be infinite. If the measured resistance (pointer swing to the right) is zero, it means that the capacitor leakage damage or internal breakdown.

2. Test 10pf-001 μ F fixed capacitor: judge whether there is charging phenomenon, and then judge whether it is good or bad. Multimeter R × 1K. Two triodes β The values are all above 100, and the through current is small. 3DG6 and other types of silicon triode can be selected to form a composite tube. The red and black probes of the multimeter are respectively connected with the emitter E and collector C of the composite tube. Because of the amplifying effect of the compound triode, the charging and discharging process of the measured capacitance is amplified, so that the swing amplitude of the pointer of the multimeter is increased, so that it is easy to observe.

It should be noted that: in the test operation, especially in the test of small capacity capacitance, it is necessary to repeatedly replace the measured capacitance pin to contact two points a and B, so as to clearly see the swing of the multimeter pointer. For 001 μ For fixed capacitance above F, R of multimeter can be used × 10K gear can directly test whether the capacitor has charging process and internal short circuit or leakage, and can estimate the capacity of the capacitor according to the swing amplitude of the pointer to the right.