(1) In the event of a power outage, ‘look, smell, ask, measure’

Look: Open the shell of the power supply, check if the fuse is blown, and then observe the internal condition of the power supply. If there are burnt areas or broken components on the PCB board of the power supply, the focus should be on checking the components and related circuit components here.

Smell: Smell if there is a burning smell inside the power supply and check if there are any burnt components.

Q: May I ask about the process of power supply damage and whether any illegal operations have been carried out on the power supply.

Measure: Before powering on, use a multimeter to measure the voltage at both ends of the high-voltage capacitor. If the fault is caused by the power failure of the LED display screen or the open circuit of the switch tube, in most cases, the voltage at both ends of the high-voltage filtering capacitor has not been discharged, which is over 300 volts. Be careful. Use a multimeter to measure the forward and reverse resistance at both ends of the AC power line and the charging condition of the capacitor. 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 and measure the ground resistance of each group of output terminals. Normally, the meter needle should have capacitor charging and discharging oscillation, and the final indication should be the resistance value of the discharge resistance of the circuit.

(2) Power on detection

After powering on, observe whether the power supply has burnt fuses and individual components emit smoke. If so, cut off the power supply in a timely manner for maintenance.

Measure whether there is a 300V output at both ends of the high-voltage filter capacitor. If not, focus on checking the rectifier diode, filter capacitor, etc.

Measure whether the secondary coil of the high-frequency transformer has output. If there is no output, focus on checking whether the switch tube is damaged, whether it is vibrating, and whether the protection circuit is working. If there is, focus on checking the rectifier diode, filter capacitor, three-way regulator tube, etc. on each output side.

If the power supply starts and stops immediately, it is in a protected state. The voltage of the PWM chip protection input pin can be directly measured. If the voltage exceeds the specified value, it indicates that the power supply is in a protected state, and the reason for the protection should be carefully checked.