How to use a multimeter to judge the quality of electronic components
A complete circuit board contains a large number of electronic components, and due to many uncertain factors, component damage is a very common occurrence. When equipment malfunctions are mostly caused by damage to components, the detection and maintenance of components become very important. How to judge the quality of a component is a skill that an engineer must learn.
When repairing, it is often necessary to first determine the electrodes of the rectifier bridge pins, which cannot be judged visually alone and is not safe enough.
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.
