iMac not booting | white screen

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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!
 
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What you are experiencing is generically called a "grey screen on startup" problem, even though on modern Macs the screen where it stalls often isn't grey these days.

In my experience, a gray screen on startup is usually a sign of a hardware problem, often an external hard drive that is problematic, or failing RAM. If you have recently attached a new peripheral, detach it and see if that helps.

Try this:
Disconnect all peripheral devices, except for the Apple keyboard and mouse. If you are using a third-party keyboard or mouse, disconnect them and reattach the Apple-supplied ones. If this resolves the issue, connect one device at a time, restarting after each one, until you've determined which device is causing the issue.

If that doesn't fix things, try this:
Remove third-party hardware upgrades such as memory (RAM) cards. If this resolves the issue, add back one item at a time, restarting after each one, to isolate the issue.

However, the first thing that I would try is replacing the PRAM battery, since they routinely go bad regardless of the age of your Mac, and they are inexpensive to replace:

Apple Coin Cell 3v Lithium
Part # 922-6476

You can find these anywhere (Target, WalMart, any drug store) as a:
CR2032
usually made by Panasonic.
I've even seen these two for a dollar at Dollar Tree stores.
 
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What you are experiencing is generically called a "grey screen on startup" problem, even though on modern Macs the screen where it stalls often isn't grey these days.

In my experience, a gray screen on startup is usually a sign of a hardware problem, often an external hard drive that is problematic, or failing RAM. If you have recently attached a new peripheral, detach it and see if that helps.

Try this:
Disconnect all peripheral devices, except for the Apple keyboard and mouse. If you are using a third-party keyboard or mouse, disconnect them and reattach the Apple-supplied ones. If this resolves the issue, connect one device at a time, restarting after each one, until you've determined which device is causing the issue.

If that doesn't fix things, try this:
Remove third-party hardware upgrades such as memory (RAM) cards. If this resolves the issue, add back one item at a time, restarting after each one, to isolate the issue.

However, the first thing that I would try is replacing the PRAM battery, since they routinely go bad regardless of the age of your Mac, and they are inexpensive to replace:

Apple Coin Cell 3v Lithium
Part # 922-6476

You can find these anywhere (Target, WalMart, any drug store) as a:
CR2032
usually made by Panasonic.
I've even seen these two for a dollar at Dollar Tree stores.
For some reason Randy's post is in a white font. Here it is in a black font for you.
 
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What you are experiencing is generically called a "grey screen on startup" problem, even though on modern Macs the screen where it stalls often isn't grey these days.

In my experience, a gray screen on startup is usually a sign of a hardware problem, often an external hard drive that is problematic, or failing RAM. If you have recently attached a new peripheral, detach it and see if that helps.

Try this:
Disconnect all peripheral devices, except for the Apple keyboard and mouse. If you are using a third-party keyboard or mouse, disconnect them and reattach the Apple-supplied ones. If this resolves the issue, connect one device at a time, restarting after each one, until you've determined which device is causing the issue.

If that doesn't fix things, try this:
Remove third-party hardware upgrades such as memory (RAM) cards. If this resolves the issue, add back one item at a time, restarting after each one, to isolate the issue.

However, the first thing that I would try is replacing the PRAM battery, since they routinely go bad regardless of the age of your Mac, and they are inexpensive to replace:

Apple Coin Cell 3v Lithium
Part # 922-6476

You can find these anywhere (Target, WalMart, any drug store) as a:
CR2032
usually made by Panasonic.
I've even seen these two for a dollar at Dollar Tree stores.
Thank you Randy.
 

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