How to check the internal circuit of AC-DC power adapter

Check the internal circuit of the AC-DC power adapter If no obvious problems are found through visual inspection and voltage testing, it may be necessary to open the power adapter and check whether there are obvious damages or abnormal conditions on the internal circuit board and components.
Check the input power supply. First, ensure that the input power supply is normal and check whether the power cord is plugged in properly and has good contact. Then, use a multimeter or voltmeter to measure whether the input voltage is within the specified range. If the input voltage is too high or too low, it may cause the power module to not work properly. At this time, check whether the power cord is damaged or the plug has poor contact, and repair or replace the power cord according to the situation. If the input voltage is normal but the power module still cannot work, the fuse inside the module can be further checked. The fuse is a protection device for the power module. When the current is too large, it will disconnect the circuit to prevent the power module from being damaged.

Use a multimeter to measure the resistance value of the fuse. If the resistance value is close to infinity or cannot be measured, it means that the fuse is damaged and a new fuse needs to be replaced. Check whether the internal connection of the power module is firm and whether there are any parts with poor soldering or looseness. At the same time, also check whether the capacitor has any abnormal conditions such as expansion or leakage. If a problem is found, re-solder or replace the faulty part. If the above steps still do not solve the problem, more complex tests may be needed, such as using an oscilloscope to measure the signal waveform and check the working conditions of each circuit element. This requires professional knowledge and instruments. It is recommended to seek the help of professionals.