My iMac turns on the start up chime sounds, you see the apple icon on the screen and then it just shuts off.  Any ideas?

My iMac turns on the start up chime sounds, you see the apple icon on the screen and then it just shuts off.  Any ideas?

Do these two resets:
SMC RESET
http://support.apple.com/kb/HT3964
Shut down the computer.
Unplug the computer's power cord and ALL peripherals.
Wait 15 seconds.
Attach the computers power cable.
Wait another 5 seconds and press the power button to turn on the computer.
The 5 second timing is important to a successful reset.
PRAM RESET
Zap the PRAM
Shut down the computer.
Locate the following keys on the keyboard: Command, Option, P, and R. You will need to hold these keys down simultaneously in step 4.
Turn on the computer.
Press and hold the Command-Option-P-R keys. You must press this key combination before the gray screen appears.
Hold the keys down until the computer restarts and you hear the startup sound for the second time.
Release the keys.

Similar Messages

Maybe you are looking for