Hello, this is my first post here as I'm in desperate need for help for my iMac 27" bought around 2011/2010. Apple won't fix it any more because it's too old and they don't have parts for it.
The computer turns on with the startup chime, I can see it tries to start, there is loading bar and it stays for for a long time (3-5 minutes) and sometimes it just never finishes to the log in screen, sometimes it turns off itself.
This unit costs over $2500 when I bought it so I was willing to fix it. I have read on google, forums and discussions and I believed that I needed to replace the hard drive, which is cheap to buy a new one so I bought a new one and followed instructions here to replace it:

It was not too difficult to replace the drive. I have followed other instructions to create a USB flash drive to install OS X.
The problem is after I replaced the drive and tried to install OS X, I am still running into the same problem, which led me to believe that the hard drive was not the issue in the first place.
And I did more reading on google, narrowed down a few discussions:







from what I've read, now I'm thinking the issue is with the video card, not hard drive. But i'm not technical enough to know this for sure and it is quite expensive to buy a new video card and find out that it still doesn't fix the problem.

I don't expect any forum member here to read all of these articles cuz they're lengthy to help me out. But if you have come across similar problem, would you have any suggestions for me before I toss this iMac to eWaste?