Why does my iMac shutdown or stagnate after a while?

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Level 1

48 points

Why does my iMac shutdown or stagnate after a while?

I have systems preferences set: energy saver>computer sleep (never) and >display sleep (15 min), yet the computer cannot be started up again after leaving it in that state for more than a half hour. When I click the space bar on my keyboard to open up the computer, I now only see a semi-bright screen. I cannot trick it by touching or pressing the off/on switch behind the bottom left screen or by striking particular keyboard keys. Why does this happen, and how can I avoid it in the future?

OS X Yosemite (10.10.5), Safari 9.0, Photo 1.0, iTunes 12.3

Posted on Mar 19, 2016 6:07 PM

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Answer 1

Best reply

Kenichi Watanabe

Level 8

41,572 points

Mar 20, 2016 8:03 AM in response to Bronco 01

You are posting in the forum category for older PowerPC Macs, but you seem to have a more recent iMac based on your profile info. If so, try doing an SMC (power management) reset

Reset the System Management Controller (SMC) on your Mac - Apple Support

For an iMac, this is basically unplugging the power cord and reconnecting it following the procedure in the document.

You may also want to do the Reset NVRAM (PRAM) procedure too

How to Reset NVRAM on your Mac - Apple Support

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Answer 2

Bronco 01 Author

Level 1

48 points

Mar 20, 2016 8:06 AM in response to Kenichi Watanabe

Kenichi Watanabe wrote:

You are posting in the forum category for older PowerPC Macs, but you seem to have a more recent iMac based on your profile info.

It has been a while since I last used this discussion forum, and its appearance and function are quite different now. I will better search for the correct forum category in future trials. Thanks for the advice.

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Answer 3

Allan Jones

Level 9

68,990 points

Mar 20, 2016 9:02 AM in response to Bronco 01

I will better search for the correct forum category in future trials.

Dear Bronco: It's not your fault but rather Apple's for refusing to use forum names that are more recognizable and/or intuitive to average end users. Apple uses "PPC" in the name of this forum yet few people today know that PPC stands for PowerPC, the processor technology Apple used prior to 2006. That covers the first three of the four broad families of iMacs. You have the fourth and current family. For future posts, the best forum for your equipment is this one:

iMac

That name once had "Intel" appended to denote the processors used from 2006 to present but I suppose it has been "Zenned" out of existence to keep the "clean" look.

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