The unstable output voltage of a switching power supply is usually caused by internal circuit faults or external environmental influences. To solve this problem, maintenance can be carried out from the following aspects:

　　Check input voltage:

　　Confirm whether the power supply voltage is stable, as excessive fluctuations may cause unstable output voltage. A multimeter can be used to measure the input voltage to ensure it is within the allowable range.

　　Check the filtering capacitor:

　　If the filtering capacitor in the switching power supply is aged or damaged, it will cause unstable output voltage. Check for expansion and leakage of electrolytic capacitors on the input and output sides, and replace them with new capacitors if necessary.

　　Check feedback loop:

　　The feedback loop is responsible for monitoring the output voltage and sending the signal back to the control circuit. If there is a problem with this part, the output voltage will be unstable. Check if the optocoupler, feedback resistor, and feedback capacitor are functioning properly.

　　Check the switch tube:

　　The switch tube is one of the core components of a switching power supply, and poor performance or damage to the switch tube can also cause voltage fluctuations. Use the diode gear of a multimeter to check the conductivity of the switch tube, and replace it if there are any abnormalities.

　　Check the PWM control chip:

　　The PWM control chip is responsible for adjusting the switching frequency to control the output voltage. Check whether the resistors, capacitors, and other components around the chip are damaged, and ensure that the chip itself is working properly.

　　Check the load:

　　If the load changes frequently or the load is too heavy, it may also cause unstable output voltage. Check if there is a short circuit or abnormal consumption of a large amount of power in the connected load devices.

　　Check the power cord and connectors:

　　Sometimes loose connection cables or poor contact of connectors can also cause voltage fluctuations. Ensure that all connections are secure and reliable.

　　Check the cooling system:

　　Excessive temperature can affect the performance of internal components in switch mode power supplies, leading to unstable output voltage. Check if the fan is running properly and if the heat sink is clean and unobstructed.

　　Recalibrate:

　　If no problems are found during the above checks, you can try recalibrating the power output. Adjust the output voltage to the correct value according to the instructions of the switch power supply.

　　Environmental factors:

　　Ensure that the working environment of the switch power supply is suitable, avoiding situations such as electromagnetic interference, high or low temperature.

　　When repairing the switch power supply, it is necessary to follow the operating procedures, disconnect the power supply before checking and replacing parts. If you do not have sufficient professional knowledge, contact professionals for repairs to avoid causing greater damage or hidden dangers.

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