820-3588-A not turn on

[andrespi]

this imac not turn on, only 1 led light before press power and after also
I already tried with another power supply in good condition, problem persists
the power button is in good condition
when pressing power the 1 led blinks once

This logic board I don't know what measures to take, thank you

 

[2informaticos]

Check for drop pulse at 12V_S5_FET.
You may need to change Q6970.

 

[andrespi]

12V_S5_FET=12.11
PP12V_G3H_FET_P12V_S5 =12.11
FET_EN_P12V_S5_R =23.14

 

[2informaticos]

You've said to note LED0301 pulsing, when press power button.
Do you note drop pulse at 12V_S5_FET at same moment???

 

[andrespi]

12V_S5_FET;it goes down to 11.3v and goes back to 12. 11 when I press power
The led turns off for an instant when value from 12V_S5_FET12.11 to 11 and it is at the same moment

 

[2informaticos]

Try changing Q6970.