Apple: Unable to Power On Your iMac

<< Symptom >>
The iMac does not power on when you push the "power" button. Nothing happen! It looks like it is not connected to a power source (but it is).

<< Rule Out Display Issues >>
First, rule out the display as the source of the issue. To be sure you're not having a display issue, press your computer's power button. If your computer has power but doesn't have any video:
1. You may hear a startup chime.
2. You may hear fan or drive noise.
3. You may see a light from the Sleep LED (if your Mac has one).
4. Pressing the Caps Lock key on the keyboard causes it to light.

<< Solution >>
1. Verify that you have a good connection from your iMac to the wall outlet by confirming the power cord and adapter are securely connected and plugged in. To check if the wall outlet is working, plug in a lamp or other electrical device.
2. If the wall outlet is working and you continue to have no power, try another power cord or adapter if available. If it works, you might need a replacement cord or adapter.
3. Disconnect all accessories that are plugged in to your computer. This includes things like printers, USB hubs, or mobile devices.
4. Hold down the power button for ten seconds. Then, press the power button again to see if the computer turns on.
5. Reset SMC.
    a. Shut down the computer.
    b. Unplug the power cord.
    c. Wait fifteen seconds.
    d. Attach the power cord.
    e. Wait five seconds, then press the power button to turn on the computer.
6. Reconnect the memory.
    a. Shut down the computer.
    b. Unplug the power cord.
    c. Remove the memory.
    d. Install the memory again.