820-00431-a no power IMac a1418

Dozer

Member
I had the same problem and want to complete this thread

PM_PWRBTN_L 3.41V and drops to about 0V by pressing power button
PM_SLP_S4 is directly after plug in the power cord 3.41V
PM_SLP_S3 is directly after plug in the power cord 3.41V as well
all S3 voltages listed in the schematics are present

PP12V_S0 was only 2,17V

U8450 Pin 2 PM_EN_FET_P12V_S0 was only 2.17V and in diode mode short to ground

after replacing U8450 I got on Pin 2 PM_EN_FET_P12V_S0 3.3V but still no progress
So I still replaced Q8450

and all problems are gone

System is working properly now.
 
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