Chosen Solution
Why is my iMac not powering on? I plugged it directly to an outlet, still will not power on. I held the power button for a minute, still will not power on. Could this be a power supply problem or logic board problem? I was working on the computer, decided to take a break for five minutes. When I came back, the computer was black.
Check your AC cord if you have another cord see if that makes a difference. Also check your power strip or UPS breaker. If you don’t hear the fan you’ll need to open the system to check the onboard diagnostic LED’s. Here’s a breakdown of the onboard diagnostic LED’s: LED 1 - Indicates that the trickle voltage from the power supply is detected by the main logic board. This LED will remain ON while the iMac is connected to the AC power. The LED will remain on even when the computer has been shut down or put to sleep. The LED will turn off only if the AC power is disconnected or the power supply is faulty.LED 2 - Indicates that the main logic board has detected proper power from the power supply when the computer is turned on. This LED will be ON when the computer is turned on and the power supply is working correctly.LED 3 - Indicates that the computer and the video card are communicating. This LED will be ON when the computer is communicating properly with the video card. If LEDs 1 and 2 are ON and you heard the startup sound, but LED 3 is OFF, then the video card might be installed incorrectly or need replacement.LED 4 - Indicates that the computer and the LCD display panel are communicating. This LED will be ON when the computer is turned on and video signal is being generated. If the LED is ON and there is no image on the LCD display panel, the LCD display panel or inverter might be installed incorrectly or need replacement. Let us know what you find.
