Model A1419 / Late 2012 / 2.9 & 3.2 GHz Core i5 or 3.4 GHz Core i7 Processor

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My 27 Inch iMac Screen Randomly Going Black

iMac (27-inch, Late 2012)

  • Processor 3.4 GHz Intel Core i7
  • Memory 32 gb 1600 MHz DDr3
  • Startup Disk Macintosh HD
  • Graphics NVIDIA GeForce GTX 680MX 2048 MB
  • OS X El Capitan, Version 10.11.6

My 27 inch iMac screen randomly goes black, the computer becomes unresponsive, and I must disconnect the AC power cord for at least 5 minutes before I can plug it in again and the computer will boot up. Waiting only 1 minute is not long enough for the iMac to power up after unplugging and replugging in the AC power cord. This started 6 months ago and I have not been able to find the problem.

I have days when it happens ten times or more a day, or I can go a day without incident. Currently it is shutting down about every 30 minutes. When it happens it is always initiated with a mouse click. It never happens with an idle machine. Now I see it also happens every time I click restart from the apple menu.

I have tried the following without success:

  • Ran Apple Hardware Test. I set the screen to full brightness and ran the extended test for over an hour to draw maximum input current. The input current to the iMac got as high as 1.22A which is 140% more than the input current I see when the iMac is running normally. I noticed the fan runs most of the time during the hardware test. NOTE: I have never heard my fan running during normal operation.
  • Reset the NVRAM.
  • Ran Disk Utility.
  • Disconnected all peripheral devices except the keyboard and mouse.
  • Swapped out the keyboard and mouse.

Any suggestions as to where the problem might lie?

Answered! View the answer I have this problem too

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Albeit in years past Macs didn't have much of a problem with viruses, today they do have. 70% of the machines I get in are infected. That's what happens when you get big, you become a target.

Forget the free virus protection programs, as those machines also come in infected.

I recommend Symantec Endpoint Protection or WebRoot.

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I would add you likely need to reformat the drive and install a fresh copy of the OS. But before you restore your backup or install any apps make sure you have scanned them and only get apps from a reliable source as some freebee's are infected with Trojan's or other Malware.

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Thank you. So you believe this is a virus. Symantec Endpoint Protection is out of my price range so I will purchase WebRoot. Is it safe to reinstall my files from Time Machine after I reinstall a new copy of the OS?

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Howard, your Time Machine Backup will be infected, so run your anti-virus on it before moving the data.

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Dan & Mayer,

Thank you.

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Come back and let us know if this fails to fix the issue.

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Howard will be eternally grateful.
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