Multimeter on the judgment of electronic components good and bad skills
The complete circuit board contains a large number of electronic components, because of many uncertain factors, component damage is very common. When equipment failure is caused by the majority of component damage, then the detection and repair of components is very important, how to determine the quality of a component is an engineer must learn the skills.
Often in the maintenance of the first to determine the rectifier bridge pin electrode, the visual alone is unable to judge, but also not enough insurance.
In the judgment of the rectifier bridge pin electrode, we can use the multimeter for the Po help. R × 1K gear state, with the black pen of the multimeter touch any one of the bridge stack pin, the red pen is to test the other pins. At this time, if the multimeter shows infinity, you can judge the black pen touching the pin for the output of the bridge stack positive pole, if the display range of 4K-10K ohms, then, the black pen touched the pin for the negative pole, red and black pen positive and negative judgment, the rest of the pins is the AC input.
Use a multimeter to determine the positive and negative digital tube
Light-emitting digital tube is mainly designed for displaying numbers, but it is very widely used. So, in the maintenance process, how to determine whether the light-emitting digital tube is damaged?
Similarly, here you can still use the multimeter detection, the use of R × 10K file and R × 100K file. First use the red nose with the digital tube "ground" lead end touch, when the black pen is measured in turn other lead end, if the test results for all segments of the light normal, then the digital tube is intact; if one of the section does not light, then the digital tube has been damaged.
Measurement of the nominal resistance of the potentiometer
When judging the potentiometer, you should first measure the nominal resistance of the potentiometer. How to measure the nominal resistance of potentiometer?
Adjust the resistance of the multimeter gear, the "2" end as a mobile contact, ohm file if the pointer does not move, the resistance value does not move, the potentiometer is damaged. Subsequently measure the potentiometer movable arm with the contact of the resistor piece whether there is a problem. You can use the multimeter ohm gear "1, 2" or "2, 3" end of the resistor shaft counterclockwise rotation to near the "off" position, that is, the smallest resistance, and then Slowly rotate the shaft clockwise, the resistance slowly become larger, when the shaft reaches the limit position, the resistance value should be similar to the nominal value of the potentiometer.
The important role of crystal oscillator in the circuit board
Crystal oscillator, also called crystal oscillator, is an electronic component made of quartz. Crystal oscillator is also referred to as quartz oscillator, used as an important component of the clock circuit, but also the computer network card, graphics card and motherboard and other equipment, the reference frequency provider.
When testing the crystal oscillator, first use the multimeter R × 10K file to detect the resistance of the crystal oscillator. If the detection result is infinity, it means that the crystal does not appear short circuit and leakage phenomenon. After testing the resistance is normal, with a test pen inserted into the test socket, and pinch any one of the pins with your fingers, the other pin is touching the top metal of the test pen, such as the test pen is bright (neon bubble), then the crystal oscillator is intact. On the contrary, the crystal has been damaged.
