Chosen Solution
So far you’ve proved the power supply is responding. If the computer it’s self is still not making any noise or visual change on the screen when you attempt to start it you have still a deeper problem. The best thing here is to open the system and see what the diagnostic LED’s tell you. Here’s the IFIXIT guide you’ll need to review: iMac Intel 24" EMC 2134 and 2211 Diagnostic LED’s Let us know what they say.
