2011 27” iMac blank screen

[MacOS2012]

Afternoon folks. Brand new poster with an old problem. I have a 2011 27” iMac 3.1ghz i5 16Gb of ram. 1TB HDD model-a1312 I bought off eBay about a month or so ago. Two weeks ago I was in the middle of a zoom meeting when my Mac crashed. I booted it back up and finished the meeting then shut it down. The next morning I tried to power it up and I got a pink screen, stuck in a boot loop and then suddenly a white screen appeared. So now the issue, I took my Mac apart to remove and bake the video card, which I did via many online people saying it worked for them. I baked it @ 390F for 8minutes, let it cool for an hour or so then put it back together, making sure all wires were seated properly. So after getting it assembled, I powered it on.... I get the chime, but the screen does not light up. And after about 30 seconds of that, the fans kick into overdrive. So I powered it down. With that info, what did I do wrong? Any suggestions what might be the issue? Or Fix?

 

[geleos27]

Probably your GPU finally dead. It's pretty easy to check. Remove LCD and turn on mac without it.
Count how many green lights mainboard shows.
If you have only 2 - GPU dead or have no propper contact in socket with manboard, if you have 3 - probably gpu are fine and you have to check propper connection from all cables from LCD to mainboard and Powersupply. (Should be 4 connected: 2 to MB, 2 to power)

Also i recommend to find photos of same GPU in google and compare, does all components are in place. Maybe you knock away some small SMD.
Also check GPU crystal for damage on corners. - if have any - chip most likely die.


Information about replacement GPU for compatible ones (starting from ~40$): https://forums.macrumors.com/threads/2011-imac-graphics-card-upgrade.1596614/