Summary of common electronic components identification and detection methods (below)

3. Inductance and inductance components can be summarized into two categories: one is self-inductance coils, such as antenna coils, tuning coils, blocking coils, lifting coils, frequency stabilization coils, deflection coils, etc.; the other is mutual inductance Transformers, such as power transformers, audio transformers, oscillation transformers, intermediate frequency transformers (mid-week), etc. Inductance is denoted by L on the circuit diagram. The unit of inductance (self-inductance coefficient) is Henry, expressed in H. The method of measuring inductance: the broken wire of the coil can be checked by the ohm gear of the multimeter, and can be partially or completely rewound during repair; Coil disconnection often occurs in the connection terminals (such as disconnection due to deseldering or force), which can be found by careful observation. Coil short circuit is mostly broken down due to the reduction of insulation force of the wire after damp. Due to the small resistance of the general coil, it is not easy to find coil short circuit (especially local short circuit) with multimeter. The better way is to use Q meter or bridge and other instruments to measure to see whether the inductance value and Q value are consistent with the normal value. During repair, the short circuit can be rewound or filled with appropriate insulating materials. When the coil turns are loose and light, it can be reinforced with insulating glue, and when it is heavy (there are some or all disorderly lines), it can be partially or completely rewound.

4. Diode Crystal diode is referred to as diode, which is a commonly used semiconductor device with a PN junction. Method of measuring diode: mechanical multimeter judges the positive and negative poles of the diode: dial the multimeter to the R× 100Ω gear, and connect the red and black pens of the multimeter to the two electrodes of the diode. if the resistance value indicated by the multimeter pointer is less, the black pen is connected to the positive pole of the diode and the red pen is connected to the negative pole of the diode; If the resistance value indicated by the multimeter pointer is greater than 100 KΩ, the black pen is connected to the negative pole of the diode, and the red pen is connected to the positive pole of the diode. This is because when the multimeter uses the resistance profile to measure, the black stylus is connected to the positive pole of the battery in the meter, and the red stylus is connected to the negative pole of the battery in the meter. Judging the quality of the diode: dial the multimeter to the gear of R× 1000Ω, and measure the forward and reverse resistance of the diode with the multimeter. A good diode forward resistance value is usually: germanium tube is 500Ω ~ 2KΩ, silicon tube is 3KΩ ~ 10KΩ, and reverse resistance value is usually greater than 100 KΩ (silicon tube is larger); The less the forward resistance, the better, and the greater the reverse resistance, the better. If the measured reverse resistance value is very small, indicating that the diode has lost the role of one-way conduction; if the measured positive and reverse resistance value is very large, indicating that the diode has been damaged (close to open circuit). According to the material, diodes can be divided into germanium tube and silicon tube. Their more prominent feature is the difference in threshold voltage (or turn-on voltage), usually 0.2~0.4V for germanium tube and 0.6~0.8V for silicon tube. It can be measured by transistor characteristic plotter.

5. Triode Semiconductor triode is a semiconductor device with two PN junctions inside and three electrodes outside. There are PNP and NPN forms. Distinguishing tube type and base (B pole): According to the characteristics of small forward resistance and large reverse resistance of transistor p-n junction, the type of tube base and tube (PNP type or NPN type) can be distinguished. The method of measuring triode: dial the multimeter to the gear of R× 100Ω or R× 1kΩ, first assume that one pin of the tube is the "base", connect the "base" with the red pen of the multimeter, and connect the black pen to the other two pins respectively. if the resistance value indicated by the multimeter pointer is less, the red pen is connected to the base to be found, and the tube is PNP type; then the red and black pens are switched (I. e. the black pen is connected to the "base" and the red pen is connected to the other two pins respectively). if the measured resistance values are large, the base of the above assumption is correct. If the red pen is connected to the "base", the resistance value measured by the above method is large, and the black pen is connected to the "base", and the red pen is connected to the other two pins respectively), then if the measured resistance value is small, the connected "base" is the base of the NPN tube. If the resistance value measured by the above method is larger and smaller, the original assumption of the "base" is wrong, so it is necessary to assume that the other pin of the tube is the "base" again, and then measure until the above requirements are met. Distinguishing emitter (e pole) and collector (c pole): for PNP type tubes, first assume that the red stylus is connected to the c pole and the black stylus is connected to the e pole, and the two poles B and c are pinched by hand (but B and c cannot be directly contacted). through the human body, it is equivalent to connecting a bias resistor between B and c to read out the resistance value between c and e.