14V would be closed to 15V. It's possible that pin7 voltage has exceeded 15V upon power on and FAN7554 have function momentarily and shutdown due to defective components on its load. You can confirm this by placing dc voltmeter on output connector and monitor it upon power on.
You can also monitor output of FAN7554 for inverter output of around 20khs to confirm inverter IC was functional. Place your multimeter probe ( with Frequency counter capability ) to FAN7554 pin6. Power on power supply and monitor a short 20khs signal. This therefore confirms that inverter circuit was functional and you have defective components on output and feedback circuit. You test each component for short, changed value, bulging capacitor need to be replaced.
good luck
Note:
Some power supply will shut down its output if it doesn’t have required load. Unless you knew that your power supply have normal output even without load.
You can also monitor output of FAN7554 for inverter output of around 20khs to confirm inverter IC was functional. Place your multimeter probe ( with Frequency counter capability ) to FAN7554 pin6. Power on power supply and monitor a short 20khs signal. This therefore confirms that inverter circuit was functional and you have defective components on output and feedback circuit. You test each component for short, changed value, bulging capacitor need to be replaced.
good luck
Note:
Some power supply will shut down its output if it doesn’t have required load. Unless you knew that your power supply have normal output even without load.
Last edited: