Hi.
This power supply is function only for 5 seconds, and then stops working.

There are good pulses in pin 9 of NCP1381, but this pulses decreases its amplitude when they reach the gate of output power switch mosfet. (also pulses are distorted)

This pulses goes trough a 470 ohms resistor (R64) and a ¿transistor? (Q5) from pin 9 to mosfet's gate.

Probably Q5 is a bipolar PNP transistor, but is impossible to know. (there is no schematic, and transistor seems damaged)

All electrolytic capacitors has been changed, and also R83. (475 ohms)

Can anybody help me to locate a equivalent transistor? (the body of the transistor are marked as 350A)

Thanks.

PS: Q5 seems very very likely as Q1 in the schematic below.

This power supply is function properly now.

Q5 is as I thought a PNP bipolar transistor. The problem, without schematic, is to get one with similar characteristics to replace it, then I saw a similar transistor (Q1) in the same power supply but in a different circuit: the PFC circuit.

Fortunately I have another identical power supply, but without Q5, (have a few components on it) but Q1 transistor in PFC circuit was there, so I take it and put it in Q5's place.

Now the drive pulses for the power mosfet are good and the psu works like a charm.

Probably a good equivalent would be a 2STR2230 transistor. ( BJT, PNP, -30V, -1.5A, SOT23)

I hope this information could help someone else.

Regards.