Repair of a switching power supply can be done in two steps
In case of power failure, "look, smell, ask, measure"
Look: open the shell of the power supply, check whether the fuse is blown, and then observe the internal situation of the power supply, if you find that the power supply PCB board has a burnt place or components rupture, you should focus on checking the components here and related circuit components. Asset Management
Smell: Smell the inside of the power supply to see if there is a pasty odour, and check if there are any burnt components.
Ask: Ask how the power supply was damaged and whether it was operated illegally.
Measure: Before not powering on, use a multimeter to measure the voltage at both ends of the high-voltage capacitor first. If the switching power supply does not vibrate or
If the switching power supply does not vibrate or switching tube open-circuit caused by the failure, in most cases, the voltage on both sides of the high-voltage filter capacitor has not been discharged to mourn, this voltage is more than 300 volts, need to be careful. Use a multimeter to measure the positive and negative resistance and capacitor charging at both ends of the AC power line, the resistance value should not be too low, otherwise there may be a short circuit inside the power supply. Capacitors should be able to charge and discharge. Disconnect the load, respectively, measure the resistance of each group of outputs to ground, when normal, the needle should be capacitor charging and discharging swing, * should be indicated for the discharge resistance of the road resistance value.
Charging test
After power on to observe whether the power supply has burned insurance and individual components of smoke and other phenomena, if any to cut off the power supply in time for maintenance.
Measure the high-voltage filter capacitor on both sides of the 300-volt output, if not, should focus on checking the rectifier diode, filter capacitors, etc..
Measure the high-frequency transformer secondary coil output, if not should focus on checking whether the switching tube is damaged, whether the vibration, whether the protection circuit action, etc., if there should focus on checking the output side of the rectifier diode, filter capacitors, three-pass regulator, etc..
If the power supply starts to stop, the power supply is in a state of protection, you can directly measure the PWM chip protection input pin voltage, if the voltage exceeds the specified value, it means that the power supply is in a state of protection, you should focus on checking the reasons for the production of protection.
