Multimeter on the judgement 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 judge the quality of a component is an engineer must learn the skills.
Often in the maintenance of the first to judge the rectifier bridge pin electrode, visual alone is not able to judge, but also not enough insurance.
In the judgement 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 piles of pins, the red pen is to test the other pins. At this time, if the multimeter shows infinity, it can be judged that the black pen touches the pin for the output of the bridge stack positive pole, if the display range of 4K-10K ohms, then, the black pen touches the pin for the negative pole, the red and black pen positive and negative judgement, the rest of the pins is the AC input.
Light-emitting digital tube is mainly designed for displaying numbers, but it is very widely used. So, in the overhaul process, how to determine whether the light-emitting digital tube is damaged?
Similarly, you can still use a multimeter to detect the use of R × 10K 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.
When judging the potentiometer, you should first measure the nominal resistance of the potentiometer. How to measure the nominal resistance of the potentiometer?
Measurement of 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 resistance 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, then Slowly rotate the shaft in the clockwise direction, the resistance slowly becomes 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 computer network cards, graphics cards and motherboards and other equipment, the benchmark frequency provider.
In the detection of the crystal oscillator is the time, first with a multimeter R × 10K file to detect the resistance value 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 test pen on the top of the metal, such as the test pen is bright (neon bubble), then the crystal oscillator is intact. On the contrary, the crystal has been damaged.
