Chosen Solution
My iMac doesn’t turn on. On the logic board is only the first 1 Diagnostic LED turned on. No chime, no fans, no hdd. The power Button is okey. What i find is: The 4st PIN on power supply output connector shows 12,05V The 6st PIN on power supply output connector shows 4,95V The 1st PIN of J600 shows 12,05V The PIN 2 and PIN 3 shows 0 - 0,2V PIN 4 of power supply output connector is railed to PIN 2 and 3 of J600 but they doesn’t have 12,05V It is correct? Or should they have also 12,05V? Is the power supply fail or maybe the cables from power supply to logic board?
I checked some rails: PP3V3_S5_REG = 3.3V OK! PP3V42_G3H_REG = 3.4 V OK! PP12V_S5 = 12.04V OK! ‘‘‘PP5V_S3_REG = 0.1 V NOT OK! ’’’ ‘‘‘PP5V_S3_REG is shorted to the GRD. ’’’ What could it be?
