No power on

Dell nps-200pb-73m
no power on but sb +5v is ok (purple)
pl send me solution

If sb +5 is ok then check one by one these component :-
check main swithing transistor for open
check diode, capesetor and 3.3 ome resitor it may be open after then check
+ 12 to +18 volt for pwm ic and ,

if votage is not missing then change pwm ic