One of my friends Yamaha PA-300B power pack was out of order because of lightning strike.
Symptoms: No output power
I checked the fuse it is working, I removed the fuse & fixed 100W tungsten bulb to see if there is any short circuit.
When AC power is connected, if bulb remains in the state of shining filament then there is short circuit present, but bulb is not in that state.
So it shows there is no short circuit in primary section, but no out in the secondary section.
I found STRW6253 is controlling the chopper transformer.
Once I replaced the STRW6253 the power supply begins to work
