How to use a multimeter to detect whether the charger is good or bad
The first method: Use the resistance range or diode range of the multimeter to check whether the power incoming line is open circuit.
You can also plug in the charger and use the DC voltage setting to measure whether there is a DC voltage of nearly 300V on the high-voltage filter capacitor (EJ). If there is still no DC voltage, use the AC setting to test whether there is AC voltage on the power incoming line (BG). 220V input. Use this to rule out whether the fault is caused by a broken wire.
The inspection steps are as follows:
1. Use the resistance or diode setting of a multimeter to measure BC, BD, GH, and GI in sequence, and the result should be a path. If any one doesn't work, that part is faulty. For example, if the measurement shows that GH is on but GI is off, it means that the common mode filter is open (possibly due to desoldering of the pins).
2. Then, use the diode tester of the multimeter to measure the forward voltage drop of the four diodes, and measure D→E, I→E, J→I, J→D in order (pay attention to the polarity) to see if the value is normal. If not, Normal, the diode should be damaged.
After completing the above steps to troubleshoot, you can basically find the problem. When these components are subjected to vibration, the components will loosen, resulting in desoldering and poor contact. After desoldering, you cannot see it if you don't look carefully, and some are not visible at all, so it is recommended to re-solder these components. For the transformer, it can be removed and inspected.
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 use an electrical barrier to test the primary. If the resistance is dozens of ohms, it means it is intact, otherwise it is damaged.
Test method: Connect one test lead of the multimeter to the core, and connect the other test lead to the outer core. Compare the voltage read on the voltage block of the multimeter with the nominal value. If it is around 7V, then it is good.
