After attempting to swap out the GPU on my 2011 21.5 inch iMac, it refuses to boot. After plugging it in and pressing the power button the fans will spin up for a moment then stop for several seconds, this will repeat but nothing else happens. I’ve replaced the old (working) GPU and it’s no different. Any advice on what it might be? Thanks a million!
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No LED diagnostics lights indicates no power to the logic board. Recheck your connections on PSU to logic board.
On this repair I prefer to go with the 661-5969 661-5968 Video Card AMD HD 6970M 2GB For iMac 27" Mid 2011 A1312
Why? because the original cards just fail, getting a used one is a likely failure scenario. I get this one out of Hong Kong but right now it’s taking a month to get. I have not had one of these new cards fail to date. Cost is just under $200.
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You need to check if the CPU is correctly in the socket and make sure you don’t have a bent pin in the socket.
Did you properly load the pressure plate? Just like changing a tire you need to slowly increase the pressure evenly across all of the screws tighting them in a zigzag pattern.
No diagnostic LED’s tells me you have a short, likely you mounted the chip incorrectly.
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Cheers for the reply. I swapped out the graphics card, not the CPU (Easy to misread!). Have done a little bit of testing, I tried powering the logic board without the graphics card, or much else attached, and LED1 does light up, but nothing happens when I hit the start button, tried the same thing with the GPU back on and the same thing occurred. I'm wondering if I've killed the Power Supply? It feels like it is able to supply a trickle to the logic board but not enough to power up the machine. Does that sound likely? It is definitely possible that I accidentally touched the soldered connecters when I was taking it out.
Got to get my glasses checked ;-} Sorry ;-{ Had CPU on the brain!
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Did you try safe mode or try running the onboard diagnostics?
Reference: Mac startup key combinations
von Dan
Thanks for the reply. Unfortunately it isn't even getting that far. It's showing no lights on the logic board, no chime and nothing on the screen. Just the occasional puff of the fans.
von Stephen Nicholls