iMac 2011 no boot white screen

[mitchino]

My iMac 2011 has been playing up recently. It chimes on start up then shows a progress bar. When it reaches about 2/3 of the way along, it shows a blank white screen, then either nothing happens, or it reboots itself and the same thing happens.

I have tried SMC reset, zapping nVRAM, single user, verbose, recovery, online recovery and nothing has worked. Have not tried booting from external disk - should this be the next step?

 

[Fishrrman]

Failed GPU?
That was a common problem with Macs in 2011...

 

[mitchino]

I know I had another one that died that way. It was obvious the graphics card had gone on that one, it didn’t have a white screen, it had stripes and all sorts. This one still displays startup disk options, and displays text if I start in verbose mode. It just never finishes starting up.

 

[MBAir2010]

My 2010 spare macbook air was doing the same thing, 2/3 then stop white screen
then after 30 minutes Catalina popped up and just crawled.
which messed up my external HD.
i rebooted and the MBA and shut down.

what needs to be done is a option key press during restart
erase disk or repair disk
reboot in snow leopard. Either usb or recovery.
if your iMac can get that fa.
Also double check the Ram slots
One could be loose, which is a long shot tho

 

[cMP MACPRO]

Failed gpu. Gpu burned out. I am having the same problem right now. I’ve had that a time ago and replaced the gpu and worked. These ,,older,, iMacs often have problem with failing gpu. Like the 2011 MacBook Pros.