Quick repair steps for common faults of switching power supply
1. At the moment of power-on, after the light bulb flashes for a while and then goes out gradually, the power supply is normal from the input to the rectification and filtering, and the fault should be in the back circuit. Otherwise, the power fuse or the input filter inductor is open.
2. If the rectifier and filter circuit is normal, check whether there is 310V voltage at both ends of the switch tube. If not, then the sampling resistor R0 or the primary of the transformer is open.
3. If the voltage of the switch tube is normal, check whether the switch tube drive circuit has a voltage of several volts to a dozen volts, if not, check the starting resistance and the drive circuit.
4. If the drive has voltage and the switch tube is normal, the self-excited winding is faulty or the feedback circuit is faulty.
5. If the light bulb is always on, the switch tube is broken down (short circuit) or the rectifier bridge is broken down (short circuit).
6. If the bulb turns on and off periodically, the load has a short-circuit fault, and the load can be detected.
7. If the replacement switch tube breaks down for many times, check whether there is an open circuit fault in the peak voltage elimination circuit and the load.
8. After the above maintenance steps and the detection of the load voltage is basically normal, the switch K can be closed. If the output is normal when the test is performed again, it means that the switching power supply has been repaired.
Note: The negative feedback circuit of the switching power supply and the secondary of the transformer must not be opened, otherwise other parts of the circuit will be damaged.
