APPLE iMac A1311 ,no power

[amennone]

Main board : 820-3126-A
Power : OT8043-290H R03BE9-0008I- apple P/N: 614-0444
EMC 2428
Problema , alla pressione del tasto power(S5010) tutto spento , led 501acceso .
Sui pin dell'alimentatore sono presenti :
Pin 6 4v6
Pin2 12v
Sul pulsante power sono presenti 3v3 , che alla pressione si genera il segnale SMC_ONOFF_L , il quale va al pin 104 di U4900 = H8S2117 LFBGA
ho difficoltà nel capire quale sequenza , quando arriva il segnale SMC_ONOFF_L, deve
eseguire U4900 per attivare l'alimentatore

[mon2]

Main board : 820-3126-A
Power : OT8043-290H R03BE9-0008I- Apple P/N: 614-0444
EMC 2428
Problem, when pressing the power button (S5010) all off, led 501 on.
On the pins of the power supply there are:
Pin 6 4v6
Pin2 12v
On the power button there are 3v3 , which when pressed generates the signal SMC_ONOFF_L , which goes to pin 104 of U4900 = H8S2117 LFBGA
I have difficulty in understanding which sequence, when the signal arrives SMC_ONOFF_L, should
run U4900 to activate the power supply

[amennone]

Problem, when pressing the power button (S5010) everything is off, led 501 is on.
On the power supply pins there are:
Pin 6 4v6
Pin2 12v
On the power button there are 3v3, which when pressed generates the signal SMC_ONOFF_L, which goes to pin 104 of U4900 = H8S2117 LFBGA
On L7710 there are 3v3, on L7750 0 Volts

PP12V_G3H_ACDC 12v O.K.
=PP12V_G3H_S5_FET
=PP12V_G3H_3V42
PP12V_S5_RSN o.k

U7700= ISL62383
pin4 = 5v
pin5 = 5v
pin12= 3V9
pin17= 12v
pin24= 0v PM_EN_P5V_S3_REG
PM_EN_P5V_S3_REG , from the diagram is generated by U6900 , these are the voltage values

U6900= 74LVC08
pin1= 0v
pin2= 3v2
pin3= 0v
pin4= 0v
pin5= 0v
pin6= 0v
pin7= GND
pin8= 0v
pin9= 0v
pin10= 0v
pin11= 0v
pin12= 0v
pin13= 3v2
pin14= 3v3

The power supply is working, if I put pin1 of the J601 connector to ground, PP12V_S0_PS is present
a little help on how to proceed, thanks.

[mon2]

Remove all power. Measure the resistance to ground of each inductor (usually grey in color; 2 leads). Checking for a possible shorted power rail.

[amennone]

With a bench power supply I powered PP12V_G3H_ACDC, the 501 LED is on, I measure a consumption of about 400 milliamps, it is known that it heats U1800