Chosen Solution
My imac 21.5 inch cannot turn on..nothing happen when I press the button on..I already check the electrity and fuse..what else I can do? How to repair by my self?
Use almost any of the guides to get the frame off, this one will do: iMac Intel 21.5" EMC 2428 Power Supply Replacement Open it up and observe the LED diagnostic lights to the right of the RAM slots and tell us what you find.
Have you tried resetting the SMC? See http://support.apple.com/kb/ht3964