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Old Apr 20, 2011, 08:20 PM   #1
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Join Date: Dec 2006
Location: New Jersey
27" iMac won't boot after power outage

Just had a breaker trip and I was unable to start my iMac afterward the power came back -- I had the same exact issue a few weeks ago after an outage -- in a different apartment (so it's probably not the electric from the outlet at fault)

Hitting the power button causes the drive to spin up and fans to go on, but no chime and no screen.

Resetting the SMC does nothing. Same results.

However, I was able to remove two of the four SO-DIMM modules (the two on the right side) and the system booted. I powered it down and put the RAM back in and it booted fine.

Any ideas? Logic board? Did I just need to clear the RAM in order to get it to go? I've not experienced anything quite like this before.
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Old Apr 20, 2011, 08:54 PM   #2
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Has happened to me a couple of times. I unplugged it, hit the power button and then plugged it back in. Powered on like normal.

Sucks living at the end of a grid.
Peter: Fox has one of those new reality shows at eight, "Fast animals, slow children"
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Old Apr 20, 2011, 11:19 PM   #3
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Do a SMC reset by:


*Shut down the computer.
*Unplug the computer's power cord and all peripherals.
*Press and hold the power button for 5 seconds.
*Release the power button.
*Attach the computers power cable.
*Press the power button to turn on the computer.
27" iMac i5, SSD, 24 GB RAM; MBA 11.6" 1.5GHz 8GB RAM 256GB SSD; iPad; iPhone 5S; Multiple HP Printers; OWC EHDs; Nikon D7100 DSLR
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Old Apr 21, 2011, 09:28 AM   #4
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I am buying a 21.5 iMac on the refresh...
Run a APC power back up on my PC, we get a lot of bumps on the AC line but my PC never blinks, just keeps on going...

My new iMac will get plugged into the APC for sure...
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Old Jun 13, 2011, 02:25 PM   #5
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If anyone runs into the same problem -- this was caused by a bad SO-DIMM. Apple replaced the memory over the weekend and it's working perfectly.
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Old Jul 17, 2013, 04:03 AM   #6
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Mac won't turn on after power outage

I had the same problem. No matter what I did. That being "holding the power button down, checking the breaker, unplugging and plugging it back in. Making sure there was in fact power to the plug itself, by plugging in a lamp. I found another post on the internet that said, "Unplug the mac from the back of it. Not from the plug in." Then reconnect the wire ...again at the back of the Mac. Worked great and turned on no problem. (I wonder if it's some sort of protection "thing"?" Hope this helps some folks who are experiencing the same thing!!
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