Common electronic component testing experience and skills

A large number of electronic components are used in electronic devices. Most of the failures of electronic components are caused by failure or damage. Therefore, how to correctly detect electronic components is particularly important. This is also a skill that must be mastered by electronic maintenance personnel. I have accumulated some common electronic component testing experience and skills in electrical appliance repair for your reference. 1.

A large number of electronic components are used in electronic devices. Most of the failures of electronic components are caused by failure or damage. Therefore, how to correctly detect electronic components is particularly important. This is also a skill that must be mastered by electronic maintenance personnel. I have accumulated some common electronic component testing experience and skills in electrical appliance repair for your reference. 1.

A large number of electronic components are used in electronic devices. Most of the failures of electronic components are caused by failure or damage. Therefore, how to correctly detect electronic components is particularly important. This is also a skill that must be mastered by electronic maintenance personnel. I have accumulated some common electronic component testing experience and skills in electrical appliance repair for your reference.

1. Test the polarity of each foot of the rectification Bridge

The multimeter sets the R × 1k block. The black table pen is connected to any pin of the bridge heap, and the red table pen tests the remaining three feet successively. If the reading is infinite, the black table pen is connected to the positive pole of the bridge heap output, if the reading value is 4 ~ 10 k Ω, then the black table pen pin is the negative output pole of the bridge heap, and the other two pins are the AC input end of the bridge heap.

2. judge whether the crystal oscillator is good or bad

First use A multimeter (R * 10 K block) 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 another pin on the metal part at the top of the test pen. If the test pen is red, it indicates that the crystal oscillator is good. If the test pen is not bright, it indicates that the crystal oscillator is damaged.

3. Unidirectional Thyristor Detection

Use the r×1k or r× 100 Block of the multimeter to measure the positive and reverse resistance of any two poles. If a pair of pole resistors is found to be low (100 Ω ~ Lk Ω), then the black table pen is connected to the control pole, the red table pen is connected to the cathode, and the other is extremely anode. The thyristor has three PN knots. We can determine the positive and reverse resistance of the PN junction by measuring its size. When measuring the resistance between the control pole (G) and the cathode [C), if the positive and reverse resistance are both zero or infinite, it indicates the control pole short circuit or open circuit; measurement control pole (G) when the resistance between the anode and the anode (A) is measured, the positive and reverse resistance readings should be very large. When the resistance between the anode (A) and the cathode (C) is measured, both positive and reverse resistance should be very large.

4. Polarity recognition of Bidirectional Thyristor

Two-way thyristor has primary electrode 1, primary electrode 2 and control pole. If the resistance between two primary electrodes is measured with A multimeter R × 1k, the reading should be approximately infinite, the positive and reverse resistance readings between the control pole and any primary electrode are only dozens of Euro. Based on this feature, we can easily identify the control pole of two-way Thyristor by measuring the resistance between electrodes. When the black table pen is connected to the primary electrode 1. The forward resistance measured when the red table pen is connected to the control pole is always smaller than the reverse resistance. Therefore, we can easily identify the main electrode 1 and the main electrode 2 by measuring the resistance size.

5. Check the quality of the luminous digital tube

First, set the multimeter to the R * 10 K or R * l00k block, and then connect the red table pen to the "Ground" Lead-out end of the digital tube (taking the common overcast digital tube as an example, the black table pen is connected to other leading terminals of the digital tube in sequence, and the seven sections should emit light respectively. Otherwise, the digital tube is damaged.

6. Determine the electrode of the junction FET

Place the Multimeter in the R * 1k block, use the black table pen to contact the pins assumed to be the gate G, and then use the red table pen to contact the other two pins, if the resistance values are relatively small (5 ~ 10 Ω), and then exchange the red and black table pens for measurement. If the resistance values are both large (∞), it indicates that they are all reverse resistors (PN junction reversely). It belongs to the n channel tube and the black table pen is in contact with the gate G. It also indicates that the original assumption is correct. If the measured resistance value is small, it indicates a forward resistance, which belongs to the P-Channel FET, and the black table pen is connected to the gate G. If the above problem does not occur, you can change the red and black table pens and perform tests according to the above method until the gate is determined. Generally, the source pole and the drain pole of the junction FET are symmetric during manufacturing. Therefore, when the gate G is determined, it is not necessary to determine the source Pole S and the drain pole D, because these two poles can be used interchangeably. The resistance between the source pole and the drain pole is several thousand euros.

7. Identification of transistor Electrodes

A multimeter can also be used to test the three electrodes of a transistor with an unclear or unlabeled model. First, switch the multimeter range to R × 100 or R × 1k electrical blocking. The red table pen is exposed to any electrode of the transistor, and the black table pen contacts the other two electrodes in sequence to measure the resistance values between them. If the measured values are several hundred euro low resistors, the electrode exposed by the red table pen is Base B, and the tube is a PNP tube. If the measured high resistance is dozens to hundreds of thousands of Europe, then the red table pen contacts the electrode is also baseline B, this tube is.

Based on the identification of the pipe type and the base B, the collector is determined by the principle that the forward current amplification coefficient of the transistor is greater than the reverse current amplification coefficient. Assume that one electrode is c and the other electrode is e. Switch the multimeter range to R × 1k electrical blocking. For the PNP tube, the red table pen is connected to the c pole, the black table pen is connected to the e pole, and the B and c poles of the tube are pinched by hand at the same time, but they cannot directly touch the B and c poles, measure a resistance value. Then the two tables are adjusted for the second measurement, and the resistance of the two tests is compared. For a PNP-type tube, the resistance is smaller once, and the electrode connected by the red table pen is the collector. For a case with a small resistance value of the type tube, the electrode connected to the black table pen is the collector.

8. determine the quality of the Potentiometer

Measure the nominal resistance of the potentiometer first. Use the Ohm block of the multimeter to test the two ends of "1" and "3" (Set "2" as active contacts). The reading should be the nominal value of the potentiometer, if the multimeter pointer is not moving, the resistance value is not moving, or the resistance value is greatly different, the potentiometer is damaged. Check whether the contact between the active arm of the potentiometer and the resistor is good. Use the Ohm block of the multimeter to test the "1", "2", "2", and "3" ends, and rotate the axis of the potentiometer in a counter-clockwise direction to a position close to "off, at this time, the lower the resistance, the better, and then the clock rotation shaft handle, the resistance should gradually increase, when turning to the extreme position, the resistance should be close to the nominal value of the potentiometer. For example, when the axis handle of the potentiometer is rotated, the multimeter pointer is abnormal, and the point contact is poor.

9. Measure the leakage resistance of large capacity Capacitors

Use a 500-type multimeter to place it in the R x 10 or R x 100 Block. When the Pointer Points to the maximum value, use the R x 1 K block for measurement immediately. The pointer will be stable in a short period of time, in this way, the leakage resistance is read.

10. Identify the infrared receiver pin

The multimeter sets the R * 1k block. First, assume that the foot of the receiving head is the grounding end, connect it with the black table pen, and measure the resistance of the other two feet with the red table pen, compare the measured resistance values (generally between 4 and ~ In the range of 7 k Q), the red table pen is connected to the + 5 V power supply pin when the resistance is small, and the other with a large resistance is the signal pin. Otherwise, if you use a red table pen to connect to the known feet, and the black table pen to test the known power supply foot and signal foot respectively, the resistance value is above 15 kb, and the pin with a small resistance value is + 5 V, the pin with a high resistance value is the signal end. If the measurement result meets the above resistance value, you can determine that the receiving header is in good condition.

11. Determine the polarity of the unsigned Electrolytic Capacitor

Discharge the capacitor short-circuit first, and then Mark A and B on the two wires. The multimeter is set to R x 100 or R x 1 K, the black table pen is connected to A lead, and the red table pen is connected to B lead, reading after the pointer remains unchanged, short-circuit discharge after the test; then the black table pen connected to B lead, the red table pen connected to A lead, compare two readings, A black table pen with a large resistance value is connected to the positive pole, and a red table pen is connected to the negative pole.

12. Test the Light Emitting Diode

Take an electrolytic capacitor with a capacity greater than 100 "F (the larger the capacity, the more obvious the phenomenon), First Use A multimeter R × 100 block to charge it, the black table pen is connected to the capacitor positive electrode, the red table pen is connected to the negative electrode, after the charging is complete, the black table pen is changed to the capacitor negative pole, and the tested light emitting diode is connected to the red table pen and the capacitor positive pole. If the light emitting diode gradually goes off after it is on, it indicates it is good. At this time, the red table pen is connected to the negative electrode of the light-emitting diode, and the positive electrode of the capacitor is connected to the positive electrode of the light-emitting diode. If the light emitting diode is not bright, re-connect the two ends of the diode for testing. If the light emitting diode is not bright, the light emitting diode is damaged.

13. Photoelectric Coupler Detection

The multimeter uses the resistance R × 100 Block, and does not select the R × 10 K block to prevent the high voltage of the battery from penetrating the light emitting diode. The red and black table pens are connected to the input end to test the positive and reverse resistance. Normally, the forward resistance is dozens of ohms, and the reverse resistance ranges from several thousand to dozens of thousands of euros. If the positive and reverse resistors are similar, the light emitting diode is damaged. Select the resistance R × 1 block for the multimeter. The red and black table pens are connected to the output end to test the positive and reverse resistance. Normally, they are close to ∞. Otherwise, the optical tube is damaged. The multimeter selects the resistance R × 10 blocks, and the red and black table pens are connected to the insulation resistance between the light-emitting tube and the light-receiving tube respectively at the input and output ends (conditional test of the insulation resistance using the M/O table, at this time, the rated output voltage of the M/O table should be slightly lower than the voltage value allowed by the optical coupler. The normal insulation resistance between the light emitting tube and the light receiving tube should be ∞.

14. photosensitive resistance detection

During the detection, dial the multimeter to the R × 1kb Ω block, and keep the light sensitivity resistance perpendicular to the incident light. Therefore, the resistance directly measured on the multimeter is the light resistance. Then the photosensitive resistance is placed in a completely dark place, and the resistance measured by the multimeter is a dark resistance. If the light resistance is several thousand euro to dozens of dry euro, and the dark resistance is several dozen euro, it indicates that the photosensitive resistance is good.

15. Laser Diode Damage Identification

Remove the laser diode and measure its resistance. Under normal circumstances, the reverse resistance value should be infinite, and the forward resistance value should be between 20 kb ~ 40kb. If the measured forward resistance has exceeded 50 kb Ω, the performance of the laser diode has declined. If the forward resistance has exceeded 90kb Ω, the tube is damaged and cannot be used any more.