I found the following steps to run through when your Mac won't turn on. First, we would want to differentiate this from a display issue, so be sure that when you press the power button:
- You don't hear a startup chime.
- You don't hear any fan or drive noise.
- There is no video on your built-in or external display
If your computer has power but doesn't display any video, it may have one or more of these similar symptoms when you press the power button:
- You may hear a startup chime.
- You may hear fan or drive noise.
- You may see a light from the Sleep LED (if your Mac has one).
- Pressing the Caps Lock key on the keyboard causes it to light.
If any of these display-related conditions occur, see Troubleshooting: My computer has no video instead. Otherwise, continue with these steps:
- Verify you have a good connection from your Mac to the wall outlet by confirming the power cord and adapter if present are securely connected and plugged in. To check if the wall outlet is working, plug in a lamp or other electrical device.
- 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 may need a replacement cord or adapter.
Note: See Apple Portables: Troubleshooting MagSafe adapters for further troubleshooting with MagSafe adapters.
- Disconnect all accessories that are plugged in to the computer, such as a printer, hub, or other mobile device.
- If your Mac supports user-installable memory, solid state drive, or hard drive, and you recently installed any of these, make sure they are installed correctly and are compatible with your computer. If possible, reinstall the original memory or drive into the computer to find out if the behavior persists afterwards.
- Reset the SMC.
- If you are still unable to start up your computer after trying each of these steps, visit an Apple Store or Apple Authorized Service Provider (AASP) for further diagnosis. If you plan to visit an Apple Retail Store, make a reservation at the Genius Bar usinghttp://www.apple.com/retail/geniusbar/ (available in some countries only).Note: Diagnostic fees may apply for issues not covered under warranty or the AppleCare Protection Plan (APP).
Welcome to Apple Support Communities!