The Magical Use of Multimeter to Detect Electronic Components
Electronic equipment in household appliances uses a large number of various types of electronic components, and electrical failures are mostly caused by failure or damage of electronic components. Therefore, how to quickly detect electronic components is particularly important. Today, Taopeitong will share with you how to use a multimeter to quickly detect various electronic components, hoping to provide help for the majority of home appliance repair practitioners
1. Measure the polarity of each leg of the rectifier bridge
Select the R×1k range of the multimeter, connect the black test lead to any pin of the bridge stack, and measure the remaining three pins successively with the red test lead. If the readings are all infinite, then the black test lead is connected to the output positive pole of the bridge stack. If the reading is 4~10k , then the pin connected to the black test lead is the output negative pole of the bridge stack, and the other two pins are the AC input terminals of the bridge stack.
2. Judging whether the crystal oscillator is good or bad
First use a multimeter (R×10k file) to measure the resistance value at both ends of the crystal oscillator. If it is infinite, it means that the crystal oscillator has no short circuit or leakage; then insert the test pen into the mains jack, and hold any pin of the crystal oscillator with your fingers. Touch the other pin to the metal part on the top of the test pen. If the neon bubble of the test pen is red, it means that the crystal oscillator is good; if the neon bulb is not bright, it means that the crystal oscillator is damaged.
3. One-way thyristor detection
The thyristor has 3 PN junctions in total, and we can judge whether it is good or bad by measuring the forward and reverse resistance of the PN junction. When measuring the resistance between the control pole (G) and the cathode (C), if the forward and reverse resistances are both zero or infinite, it indicates that the control pole is short-circuited or disconnected; measure the resistance between the control pole (G) and the anode (A). When measuring the resistance, the forward and reverse resistance readings should be very large; when measuring the resistance between the anode (A) and the cathode (C), the forward and reverse resistance should be very large.
The R×1K or R×100 range of the multimeter can be used to measure the forward and reverse resistance between any two poles. If the resistance of a pair of electrodes is found to be low resistance (100Ω～1kΩ), then the black test lead connected It is the control electrode, the red test lead is connected to the cathode, and the other is the anode.
4. Polarity identification of bidirectional thyristor
The bidirectional thyristor has the main electrode 1, the main electrode 2 and the control pole. If the resistance between the two main electrodes is measured with a multimeter R×1k, the reading should be approximately infinite, and the positive and negative resistance between the control pole and any one of the main electrodes The resistance reading is only tens of ohms. According to this characteristic, we can easily identify the control pole of the bidirectional thyristor by measuring the resistance between the electrodes. When the black test lead is connected to the main electrode 1 and the red test lead is connected to the control electrode, the measured forward resistance is always smaller than the reverse resistance. Therefore, we can easily identify the main electrode 1 and the main electrode by measuring the resistance. 2.
5. Check whether the luminous digital tube is good or bad
First set the multimeter to R×10k or R×100k, then connect the red test lead to the “ground” terminal of the digital tube (take the common cathode digital tube as an example), and connect the black test lead to other terminals of the digital tube in turn. They should be illuminated separately, otherwise the digital tube is damaged.
