Sanyo PLC-XW50 projector - bulb not turn on

Sanyo PLC-XW50 projector
Symptom: Turn on power led & fans starting to rotate but UHP bulb is not turning on.

The owner had told me the bulb life is around 310 hours. So I checked for the high voltage from ballast with aid of 45KV High voltage probe

but found the ballast is not generating high voltage. Then checked for the component failures in the ballast PCB, found four 16N25 Field Effect Transistors are defective.

After replacing the four 16N25 FETs the projector begins to work, the lamp hours exact 310 hours as the owner had told.