Introduction to the skills of judging the quality of electronic components with a multimeter
Use an electric soldering iron to remove the capacitors, resistors, and rectifier bridge used for voltage reduction
When determining the electrodes of the rectifier bridge pins, we can use a multimeter for assistance. In the R × 1K gear state, touch any pin of the bridge stack with the black pen of the multimeter, and test the other pins with the red pen. If the multimeter displays infinity at this point, it can be determined that the pin touched by the black pen is the positive output of the bridge stack. If the display range is 4K-10K ohms, then the pin touched by the black pen is the negative terminal. After determining the positive and negative terminals of the red and black pens, the remaining pins are AC inputs.
Use a multimeter to determine the positive and negative poles of a digital tube
Light emitting digital tubes are mainly designed for displaying numbers, but they are widely used. So, how to determine if the LED is damaged during the maintenance process?
Similarly, a multimeter can still be used for detection here, using R × 10K and R × 100K gears. First, use the red nose to touch the "ground" terminal of the digital tube. At this point, use the black pen to measure the other terminals in sequence. If the test results show that all segments are emitting light normally, then the digital tube is intact; If one of the segments does not light up, the digital tube is damaged.
Measurement of nominal resistance of potentiometer
When judging a potentiometer, the nominal resistance value of the potentiometer should be measured first. How to measure the nominal resistance of a potentiometer?
Adjust the resistance range of the multimeter, using the "2" terminal as the moving contact. If the pointer and resistance value of the ohm range do not move, the potentiometer is damaged. Then measure whether there is a problem with the contact between the potentiometer arm and the resistor. You can use the "1, 2" or "2, 3" end of the multimeter ohm range to rotate the resistor shaft counterclockwise to the position close to "off", where the resistance is the lowest. Then slowly rotate the shaft clockwise, and the resistance gradually increases. When the shaft reaches the limit position, the resistance value should be close to the nominal value of the potentiometer.
The important role of crystal oscillator in circuit board
Crystal oscillator, also known as crystal oscillator, is an electronic component made of quartz. Crystal oscillator, also known as quartz oscillator, is an important component used in clock circuits and serves as a reference frequency provider for devices such as computer network cards, graphics cards, and motherboards.
When testing the crystal oscillator, first use a multimeter R × 10K to measure the resistance of the crystal oscillator. If the detection result is infinite, it indicates that there is no short circuit or leakage phenomenon in the crystal oscillator. After checking that the resistance is normal, insert the test pen into the test socket and pinch any one pin with your fingers, while the other pin touches the top metal of the test pen. If the test pen lights up (neon bubble), the crystal oscillator is intact. Otherwise, the crystal oscillator has been damaged.
