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Model A1419 / EMC 2806 / Late 2014 or Mid 2015. 3.3 or 3.5 GHz Core i5 or 4.0 GHz Core i7 (ID iMac15,1); EMC 2834 late 2015 / 3.3 or 3.5 GHz Core i5 or 4.0 GHz Core i7 (iMac17,1) All with Retina 5K displays

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iMac Shuts down when watching video

Hi,

Recently I have been experiencing a phenomenon with with my 5K imac. Whenever I watch a video - either on Youtube, Facebook, CNN etc, the computer will power off completely and will not turn on for quite some time and only with a little finagaling.

When this happens I turn the computer over and I can see that there are NO diagnostics LEDS lit, even when the computer is connected to power. I keep having to do a SMC reset, repeatidly. Sometimes it can take over an hour before I can see the first LED come on, then the machine powers on and all four LEDS are lit up.

Is this a power supply issue or a logic board issue? Is there any way to get a more definitive diagnostics?

I ran the Apple Diagnostic Tool and it does it's test with no issues reported.

I formatted the hard drive and started with nothing else loaded ran Safari on Youtube and it happened again.

The other thing I did was I vacuumed the dust out of the bottom. Again no luck.

Any help would be appreciated.

Thanks!

Answer this question I have this problem too

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If the on-board diagnostic LED's are not lighting that points to a power supply, You need to start there.

Do make sure you use a good surge suppressor or a UPS. The newer iMac's appear to be more sensitive to power issues which damage things.

Next time you clean your system don't use a vacuum! You can zap your system with static. Use can'ed air instead.

Update (05/12/2018)

I would recommend you install this app: TG Pro You'll want the full version. It will allow you to see the thermal sensors and fan to see how hard your system is running. I would also recommend you run Activity Monitor it will allow you to see which process is consuming the most processing time and system resources.

You may still have a logic board issue here as well! But you need to start with the power supply.

Think of it this way... If you don't have a good foundation you can't build a strong house.

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6 Comments:

Hi, thanks for your response. I was thinking the power supply but I am curious as to why this only happens only with video? Does the video consume more power thus shutting the system down. I am a photographer and I can be using Lightroom and Photoshop for weeks and the machine works fine - the moment I forget and watch a video on the machine - it will shutdown.

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In a way it does... The CPU & GPU become process bound pulling more power. Playing YouTube video's do push your system.

Lightroom & Photoshop graphics apps can also push your system. But unlike the video's you may not be pushing the system as hard for as long a duration. If you are batch processing large images then you are likely to hit the same issue.

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Hi Dan, thanks again for the response. While I have never taken an iMac apart, I have worked on many systems and feel confident in doing the power supply myself, but if I do it - can I test it while the display is not adhered to the frame? I would hate to have to disassemble the entire machine again if its not.

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How where you sighting the diagnostic LED's? I don't even think you can see them from the outside.

Once you get the display off you'll see them. Do be careful pulling the display as you can damage it very easily! Follow the IFIXIT guide and use the proper tools!

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Flip the machine over they are just to the left of of the Apple logo when you are looking at the front of the computer. You have to look through the air slots. They are close enough to the bottom to see them.

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