Chosen Solution
Hi, My Mac suddenly crashed just when I was full screening a magazine online. Since then the iMac has not been able to boot, boot from macOS USB or go to recovery mode. It just shows a white screen (as in 1st picture)
after eg choosing WiFi for recovery mode (2nd picture). The bar loads, the Apple logo comes on it loads half ways and go to white screen
I can run the apple hardware test (AHT) however it finds no errors… I have tried swapping the HDD (AHT gives warning of missing sensor) - it doesn’t work I have running off of one ram stick (trying different modules) - it doesn’t work Is it the graphics card? Or maybe something completely different All help is appreciated
Sadly your discreet GPU board has failed you ;-{ The first thing is to fully clean out the dust as a common issue is overheating of the GPU. You’ll need to remove the the GPU board clean off the thermal paste and pads. We don’t have a 27” guide but the 21.5” will get you there! iMac Intel 21.5" EMC 2428 GPU Card Replacement Then you have two choices here, the first is baking your board to revive it or you could replace it with anther board (better one) The last option is to bypass the dedicated GPU and instead leverage the intergraded graphics services within the CPU.
