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I had an old 2011 iMac that had been sitting for awhile that would turn on and just go to a white screen. I was able to reinstall the OS. and everything started working fine. I also upgraded the memory. It worked fine for a bit and then randomly started having weird issues. Now after it powered in within a minute the following started. First the screen flashed, showed blue and black vertical lines, and then rebooted. After reboot the screen was not right, weird lines, some stuff fuzzy, and not everything in correct alignment. I rebooted. Then again with the gray and blue lines (got a picture of it this time and it is attached). Now it is back to powering on, showing apple logo, and then going to white screen. I tried resetting NVRAM and PRAM. Any thoughts on what it could be or how to diagnose further?
Sadly the GPU board has failed ;-{ iMac Intel 27" EMC 2429 (Mid 2011) Graphics Cards We don’t have guide you can follow directly, but this one will get you mostly there Installing iMac Intel 27" EMC 2429 Dual Drive Kit (HDD or SSD) Then finish removing the cables so you can remove the logic board fully on the back side is where the GPU board is located. Some people find baking it will revive it for a bit other wise its going to take a bit of hunting to find a good one.
Hi! I’ve seen this issue a couple of times, If possible could you post pictures of the lines here so we can see Adding images to an existing question -Jup :)
