Chosen Solution
This is super weird…thought it was a bad power supply so bought a new one, after install didnt work so found some strange symptoms here: Mid 2011 iMac, when the LCD display is removed from case, it will boot (makes chime and fans go on, etc). When I put display into the case (even at a slight angle and no wires hooked up, just the bottom placed in to hold it), the thing wont boot at all remove LCD, boots Install completely (with wires hooked up), doesnt boot What is going on? Is there a reed switch or something from the magnets that might be bad? Pressure switch on bottom of case? Seems VERY strange considering the scrren doesnt even need to be installed for a non-boot event to occur.
Sounds like the display is pressing on a wire, connector or other component that shuts it down. I would use a strong flashlight and go over it like you were a CSI agent and see if you can spot it.
