The measurement methods are divided into two ways: component testing and circuit board on-road testing. In line test: Disconnect the inverter power supply and measure the components on the

circuit board without removing the circuit board components. For breakdown, short circuit and open circuit faults of components, this detection method can easily and quickly find out the damaged

components, but it should also consider the impact of the components measured on the circuit board and the components in parallel on the measurement results, so as not to cause misjudgment

errors. How to detect the circuit board electronic components good or bad skills?

1. Detection of ordinary diodes: Measure with MF47 multimeter, connect the red and black pen to both ends of the diode, read the reading, and then switch the pen to measure. According to the

results of the two measurements, the forward resistance value of the low-power germanium diode is usually 300-500Ω, and the silicon diode is about 1kΩ or larger. The reverse phase resistance of

the germanium tube is tens of kiloohms, and the reverse resistance of the silicon tube is above 500kΩ (the value of the high-power diode is much smaller). Good diode forward resistance is lower, the

reverse resistance is larger, the greater the positive and negative resistance difference, the better. If the positive and reverse resistances measured are very small and close to zero, it indicates that the

diode has a short circuit inside; If the positive and reverse resistance is large or tends to infinity, it means that the inside of the pipe has been broken. In both cases the diode needs to be scrapped. In

the road test: testing the positive and negative resistance of the diode PN junction, it is easier to determine whether the diode is a breakdown short circuit or a break.

2. Transistor detection: switch the digital multimeter to the diode file, use the pen to measure the PN junction, if the positive guide passes, the number displayed is the positive voltage drop of the PN

junction to determine the collector and emitter; The forward pressure drop of the two PN junctions is measured with a pen. The one with large pressure drop is emitter e and the one with small

pressure drop is collector c. In the test of two junctions, the red pen is connected to the common pole, then the tested triode is NPN type, and the red pen is connected to the base b; If the black watch

pen is connected to a common pole, the triode under test is PNP type, and this pole is base b. After the transistor is damaged, the PN junction has two cases of breakdown short circuit and open

circuit test: In the road test of the transistor, in fact, by testing the positive and reverse resistance of the PN junction, to determine whether the transistor is damaged. The branch resistance is greater

than the forward resistance of the PN junction, and the positive and reverse resistance measured in normal times should be significantly different, otherwise the PN junction is damaged. When the

branch resistance is less than the PN junction forward resistance, the branch should be disconnected, otherwise it is impossible to judge the quality of the triode.

3.Detection of electrolytic capacitors: When measuring with MF47 multimeter, the appropriate range of the multimeter should be selected for electrolytic capacitors with different capacities.

According to experience, under normal circumstances, electrolytic capacitors below 47μF can be measured in R×1K, and electrolytic capacitors greater than 47μF can be measured in R×100. Connect

the red pen of the multimeter to the negative electrode of the capacitor, and the black pen to the positive electrode. At the moment of contact, the multimeter pointer deflects to the right by a large

margin, and then gradually turns to the left until it stops at a certain position (returning to infinity). The resistance value at this time is the forward leakage resistance of the electrolytic capacitor. The

larger the value, the smaller the leakage current and the better the performance of the capacitor. Then, switch the red and black watch pen, and the multimeter pointer will repeat the above-

mentioned swinging phenomenon.

However, the resistance measured at this time is the reverse phase leakage resistance of the electrolytic capacitor, which is slightly less than the forward leakage resistance. That is, the reverse

leakage current is larger than the forward leakage current. Practical experience shows that the leakage resistance of electrolytic capacitors should generally be more than a few hundred thousand

ohms, otherwise it will not work normally. In the test, if there is no charging phenomenon in the forward and reverse phase, that is, the watch hand does not move, it indicates that the capacitor

capacity disappears or the internal short circuit; If the resistance value measured is small or zero, it indicates that the capacitor has large leakage or has been broken down and damaged, and can no

longer be used.

On-road test: On-road test of electrolytic capacitors should only check the fault of serious leakage or breakdown, and the accuracy of slight leakage or small-capacity electrolytic capacitors test is very

poor. The influence of other components on the test should also be considered in the road test, otherwise the value read out will be inaccurate and will affect the normal judgment. Electrolytic

capacitors can also use capacitance meters to detect the capacitance value between the two ends to judge the quality of electrolytic capacitors.