How to check the quality of the charger with a multimeter
The first method: Use the resistance gear or diode gear of the multimeter to check whether the incoming power line is open.
You can also plug in the charger, and use the DC voltage gear to measure whether there is a DC voltage of nearly 300V on the high-voltage filter capacitor (EJ). 220V input. This is to rule out whether the fault is caused by the disconnection of the wire.
The inspection steps are as follows:
1. Measure BC, BD, GH, and GI sequentially with the resistance gear or diode gear of the multimeter. The results should all be channels. If any one doesn't work, that part is faulty. For example, if the measurement reaches GH, but GI fails, it means that the common mode filter has an open circuit (maybe the pins are desoldered).
2. Then, measure the forward voltage drop of 4 diodes with a multimeter diode tester, measure D→E, I→E, J→I, J→D in turn, (pay attention to the polarity) to see if the value is normal, if not It is normal, the diode should be damaged.
After completing the above steps, you can basically find the problem. When these components are subjected to vibration, the components will be loosened, resulting in desoldering and poor contact. After desoldering, if you do not look carefully, you cannot see them, and some cannot be seen at all, so it is recommended to re-solder these components. For the transformer, it can be removed and checked.
The second method: power-on test method
Adjust the multimeter to the voltage range to measure the voltage. If there is no voltage, remove the power supply and test the primary with electricity blocking. If the resistance is tens of ohms, it means it is in good condition, otherwise it is damaged.
Test method: Connect one test lead of the multimeter to the wiring core and the other test lead to the outer core, and compare the voltage read on the voltage block of the multimeter with the nominal value. If it is around 7V, then it is good.
