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?
Is this a good question?