820-3302 No light in first LED

[No-Clean]

Clean board sometimes first LED comes on and iMac powers on fine, but most times no first LED, when that is the case here are some voltages:

PP12V_G3H: 12V
PP3V42_G3H: 3.4V
PP12V_S5: 0V Diode mode 0.520
PP5V_S5: 0V Dione mode 0.375
PP3V3_S5: 0V Diode mode 0.135

Already replaced U7600, Q7880, U7880, Q7610 and Q7650 because I am tonto and was desperate, please help!

 

[2informaticos]

Change Q7950.

 

[No-Clean]

Replaced Q7950 but same thing, but that lead me to study that circuit and realized U7950 was the problem, board is happy and running again, thanks!