liteon PS-5251-5
dell P/N : W208D

It seems that only primary voltages are present in the circuit.

I need diagram schematic , Thanks any help received

---

Posted after 2 hours 28 minutes 44 seconds:
I started to check if there was voltage at the output of a code transformer (42-M530108P02 A) where a rectifier diode and a 1500uF electrolytic capacitor are welded. There is no tension at this point. So I figured the built-in TNY266 might be in trouble. I've switched this component. Then I turned the power on and the power went back on.

The tny266 was changed and the source returned to normal operation.