iMac Late 2012 27" Black Screen and Trouble Booting

[Olzer]

Hello hello,

I currently have a really frustrating problem with my iMac 2012. For about a month now I have been experiencing a unresponsive black screen, it would usually happens after the computer goes to sleep. It won't wake after sleep (completely unresponsive) however I can hear a faint fan noise. This is the only instance when I get stuck on the black screen. Now.. I also experience the same problem if I shut the computer down, it can take several attempts to get it to boot up. When I try boot it up I hear a faint fan and maybe hard drive noise but NO chime or the normal booting 'hard drive' noise. Im at the stage now where I can't even get it to boot, the last time this happened I tried for days with no luck and the only way I got it to boot was after I left it for 3 days unplugged and it worked the next time I tried it. Because of this issue my only option is to leave the iMac on and with a screensaver so it doesn't go to sleep. Have you guys got any ideas on what might be causing this? The iMac is currently off and I can't get it to boot so I can't do any system checks etc.. I have read that It could possibly be a screen connection issue? but I am very novice when it comes to the technical side of computers so I honestly have no idea. I have tried removing ram, booting with ram ejecting (get a loud beeping noise) unplugging for hours/days, all ports unplugged. I have run out of ideas. I read somewhere that there might be a build of electricity in the computer, which is why leaving it off for several days worked as it gave it time to drain the power completely? I am currently trying this again, plan to leave for 2/3 days and ill see. But any recommendations would be much appreciated!

NOTE: sorry I forgot to mention a potentially important thing. Several weeks before I started to experience the black screen my WIFI would intermittently stop working, I would have to restart the computer to get it to work again. I would click 'turn wifi on' and it wouldn't do anything (stayed off). ALSO about a week ago it seemed like my bluetooth also was having some issues, got a squiggly line through it. Not sure if related, but I get the feeling it is.. Hopefully is software related. But could these be signs of something worse? Thanks again.

Sorry for the massive spiel. First time on this forum.

Thanks in advance, Cheers!

 

[Juicy Box]

Have you reset SMC and PRAM?

PRAM:

Reset NVRAM on your Mac - Apple Support

If one or more settings stored in NVRAM don't work as expected on an Intel-based Mac, resetting NVRAM might help.

support.apple.com

SMC:

Reset the SMC of your Mac - Apple Support

The SMC is responsible for managing power on your Mac. Resetting it can resolve certain uncommon issues related to power or thermal management.

support.apple.com

Both are really easy, and it could correct your issues. Let us know.
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What are your iMac's specs? and what OS?

I have tried removing ram, booting with ram ejecting (get a loud beeping noise) unplugging for hours/days, all ports unplugged. I have run out of ideas.

That might have taken care of the SMC, but I would do it again just to be sure.

Definitely do the PRAM though, as waking and sleeping issues can be PRAM related.

 

[Juicy Box]

Do you have a Fusion Drive or HDD?

I had very similar issues on my Late 2012 iMac that progressively got worse. I knew it was the Fusion Drive, and even though it was under warranty Apple refused to fix it due to it passing their HW diagnostic tests in the Apple Store.

I took it to them many times only to get the same results. It would pass the tests, they would wipe the drive, I would restore from my BU, only to have the problems come back, each time progressively sooner.

I suspect there were bad sectors on the HDD, and each time they wiped the drive and I restored my BU, it was fine until those sectors started to be used again, then I would have slow downs, slow boots, Slow shutdowns and restarts, no boots, black screens, strange glitches (like options in the menu bar wouldn't be there when they should be), etc.

With 12 days left of my warranty, the drive totally failed. Like totally. It messed up my iMac so bad that it wouldn't even boot into internet recovery mode, nor would the Apple HW Diagnostic tool boot at first. After about two hours of trying, the "Genius" was able to get the tool to boot, and it finally showed the HDD as failed.

If it wasn't under warranty, I would have just replaced the drive myself. In retrospect, I probably should have just replaced it after Apple refused to.

I am unsure if that is your issue, but it might be worth looking into if the PRAM reset doesn't work.

 

[Olzer]

Have you reset SMC and PRAM?

PRAM:

Reset NVRAM on your Mac - Apple Support

If one or more settings stored in NVRAM don't work as expected on an Intel-based Mac, resetting NVRAM might help.

support.apple.com

SMC:

Reset the SMC of your Mac - Apple Support

The SMC is responsible for managing power on your Mac. Resetting it can resolve certain uncommon issues related to power or thermal management.

support.apple.com

Both are really easy, and it could correct your issues. Let us know.
[automerge]1595807509[/automerge]
What are your iMac's specs? and what OS?


That might have taken care of the SMC, but I would do it again just to be sure.

Definitely do the PRAM though, as waking and sleeping issues can be PRAM related.

Thanks for that, I did the PRAM about a month ago when it was getting bad. Problem is I can't get it to turn on atm and even when I do I'm scared to restart it incase it gets stuck again. I can't remember the specs off the top of my head sorry, I know its a 27" late 2012 with 32gb ram. Ill let you know when/if I can get it to turn on again. I know its not on the latest OS. Maybe El Capitan? Sorry for the lack of info.
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Do you have a Fusion Drive or HDD?

I had very similar issues on my Late 2012 iMac that progressively got worse. I knew it was the Fusion Drive, and even though it was under warranty Apple refused to fix it due to it passing their HW diagnostic tests in the Apple Store.

I took it to them many times only to get the same results. It would pass the tests, they would wipe the drive, I would restore from my BU, only to have the problems come back, each time progressively sooner.

I suspect there were bad sectors on the HDD, and each time they wiped the drive and I restored my BU, it was fine until those sectors started to be used again, then I would have slow downs, slow boots, Slow shutdowns and restarts, no boots, black screens, strange glitches (like options in the menu bar wouldn't be there when they should be), etc.

With 12 days left of my warranty, the drive totally failed. Like totally. It messed up my iMac so bad that it wouldn't even boot into internet recovery mode, nor would the Apple HW Diagnostic tool boot at first. After about two hours of trying, the "Genius" was able to get the tool to boot, and it finally showed the HDD as failed.

If it wasn't under warranty, I would have just replaced the drive myself. In retrospect, I probably should have just replaced it after Apple refused to.

I am unsure if that is your issue, but it might be worth looking into if the PRAM reset doesn't work.

Thanks for that. Not sure about the Drive sorry. I assume its HDD but I could be wrong. Its definitely out of warranty so whats your opinions on taking into apple? Will they check it and quote? Don't really want to pay a lot of $$ for it to potentially crap out again. Im very limited in what I can do atm as I can't get it to boot up, have reset PRAM recently.
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NOTE: sorry I forgot to mention a potentially important thing. Several weeks before I started to experience the black screen my WIFI would intermittently stop working, I would have to restart the computer to get it to work again. I would click 'turn wifi on' and it wouldn't do anything (stayed off). ALSO about a week ago it seemed like my bluetooth also was having some issues, got a squiggly line through it. Not sure if related, but I get the feeling it is.. Hopefully is software related. But could these be signs of something worse? Thanks again.