iMac not booting | white screen

[Macprobsolver]

Hello everyone,



After two weeks of Googling and countless YouTube videos, I'm reaching out to see if I could get some direct help. My 2012 iMac 27" froze suddenly while I was working in iMovie and stayed unresponsive for about 20 minutes. I tried to reboot the system numerous times and while the bar would get so far during the loading screen, it eventually dimmed and I would just see the white screen. I then tried everything I knew to do: safe mode, recovery mode, PRAM, diagnostics, network recovery, hardware test (short and long), SMC reset, everything is unplugged except a keyboard and mouse, and have tried re-installing OS from a USB boot drive (worked once, but then the freeze happened again about 3 minutes into using). Am I missing anything? Every keyboard short I know and have looked up eventually results in the white screen. I even tried using target disk mode hoping to run recovery from a MacBook Pro but still nothing. I've done the fsck -fy countless times from single user mode... Is my Mac broken even though there are times when I've made progress? Please help!

 

[glenthompson]

Take the memory out and verify you get the proper error on boot. Replace memory one module at a time to see if it boots properly.

Hve you tried to boot and run from just an external drive to see if the internal drive is the problem?

 

[Nguyen Duc Hieu]

Hello everyone,



After two weeks of Googling and countless YouTube videos, I'm reaching out to see if I could get some direct help. My 2012 iMac 27" froze suddenly while I was working in iMovie and stayed unresponsive for about 20 minutes. I tried to reboot the system numerous times and while the bar would get so far during the loading screen, it eventually dimmed and I would just see the white screen. I then tried everything I knew to do: safe mode, recovery mode, PRAM, diagnostics, network recovery, hardware test (short and long), SMC reset, everything is unplugged except a keyboard and mouse, and have tried re-installing OS from a USB boot drive (worked once, but then the freeze happened again about 3 minutes into using). Am I missing anything? Every keyboard short I know and have looked up eventually results in the white screen. I even tried using target disk mode hoping to run recovery from a MacBook Pro but still nothing. I've done the fsck -fy countless times from single user mode... Is my Mac broken even though there are times when I've made progress? Please help!

If you are talking about your iMac as a whole unit, then yes, it's broken.
If you are trying to isolate the defect parts, then maybe only GPU chip is bad.
Depending on where you live, replacing/reballing the GPU chip may be just not viable.
It's time to upgrade, then.

 

[Juicy Box]

Do you have a Fusion Drive?

The HDD may have failed or is failing.

My 2012 iMac 27"

Can you please post your specs.

have tried re-installing OS from a USB boot drive

Try installing to a USB drive (or any external drive), and boot from it and see if you have the same problem.

 

[Fishrrman]

OP wrote:
"and have tried re-installing OS from a USB boot drive (worked once, but then the freeze happened again about 3 minutes into using)"

You haven't told us WHAT KIND OF DRIVE is inside the iMac.
Is it:
- platter-based hard drive?
- fusion drive?
- SSD?

Sounds like you could be having a drive failure, or perhaps a graphics failure.