Method for testing the quality of chargers with a multimeter
The first method: Use the resistance range or diode range of a multimeter to measure whether the power input line is open.
You can also plug in the charger and use the DC voltage range to measure whether there is a DC voltage of nearly 300V on the high-voltage filter capacitor (EJ). If it still does not exist, use the AC range to measure whether there is an AC 220V input on the power input line (BG). To rule out whether the fault is caused by a broken wire.
The inspection steps are as follows:
1. Measure BC, BD, GH, and GI in sequence using a multimeter resistance or diode range, and the results should all be in the same path. If one doesn't work, then that part is faulty. For example, if GH is connected and GI is not connected, it indicates that the common mode filter has an open circuit (possibly due to pin detachment).
2. Then, use the diode gear of the multimeter to measure the forward voltage drop of the four diodes, and measure D → E, I → E, J → I, J → D in sequence (pay attention to the polarity) to see whether the values are normal. If not, the diodes should be damaged.
By completing the above steps of troubleshooting, you can basically identify the problem. When these components are subjected to vibration, they can become loose and cause detachment, resulting in poor contact. After detachment, if not carefully examined, it cannot be seen, while some cannot be seen at all. Therefore, it is recommended to re weld these components. For transformers, they can be removed for inspection.
The second method: power on test method
Adjust the multimeter to the voltage range for voltage measurement. If there is no voltage, remove the power supply and use the resistance range to test the primary level. If the resistance is tens of ohms, it indicates good condition, otherwise it is damaged.
Test method: Connect one lead of the multimeter to the wire core and the other lead to the external core. Compare the voltage read on the voltage range of the multimeter with the nominal value. If it is around 7V, then it is good.
