after power up no display and is dark

Hello antkook,

Thanks for using Apple Support Communities.

For more information on this, take a look at:

Troubleshooting: My computer won't turn on

http://support.apple.com/kb/TS1367?viewlocale=en_US

1. Disconnect all accessories that are plugged in to the computer, such as a printer, hub, or other mobile device.
2. 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.
   • MacBook Pro: How to remove or install memory
   • MacBook: How to remove or install memory
   • Mac Pro: How to remove or install memory
   • Mac mini: How to remove or install memory
   • iMac (27-inch, Late 2012): Installing or replacing memory
   • iMac: How to remove or install memory
3. Reset the SMC.

Best of luck,

Mario