iMac goes black – need to unplug to restart

[jayco1983]

It's a late 2015 "27 retina iMac. I've had it for at least 2 years.

I ran into this problem for the first time while running Lightroom some two weeks ago. Basically, the screen goes black. I can't restart it or force a shutdown. I have to unplug the power chord and plug it in again before it'll start up again, and there are no error notices or anything.

• I've done a diagnostic – no errors found.
• I've reset the SMC and NVRAM. Doesn't help.
• I found a youtube video of a guy describing the same issue and showing how he resolved it (ejecting the RAM then putting it back and restarting), but that didn't help me.

I tried it out in safe mode for a few days, and then it seemed to work fine, but it's hard to tell because I can't really work in safe mode. Either way, did a complete reinstall of the system a few days ago and it's been working fine, until today. I installed Photoshop yesterday evening and after a few hours of work today it started happening again.

Sometimes it takes a while for it to occur, but when it starts acting up, it will do so often unless I let the computer be for a while.

A heating issue? Power? Suggestions?

 

[AmazingRobie]

Sorry to hear of your problem, but glad you posted the issue. Hopefully someone can actually help and it's not more of Apple's planned obsolescence at play. This stinks of Timothy Crook and Jonathen Conn-Ive-ing.

 

[AndrsnH]

I've had a similar issue where mine would cut out/lose power/die at random intervals without warning and the only way to get it to turn back on was to physically remove the power cable from the back of the computer before attempting to restart.

I took mine in to the Apple Store (covered with AppleCare) in the UK and they were useless. They didn't diagnose the problem even after 3 visits. They replaced the power supply on the 3rd visit after I called AppleCare. The repair technician and the genius had a disagreement that the power supply was causing the issue.

The store managed to damage the stand of the computer, and also caused chipping to the enclosure.
They replaced the stand, however managed to chip it a second time.
They also caused chipping to the enclosure but refuse to acknowledge the damage despite the computer never leaving the Apple Store.
I had a horrendous experience with one of the rudest managers I've ever spoken to who didn't care about my concerns.

Currently have the iMac at home in the box still chipped and I have no idea if the issue has been fixed.

 

[iGeek2014]

I've had a similar issue where mine would cut out/lose power/die at random intervals without warning and the only way to get it to turn back on was to physically remove the power cable from the back of the computer before attempting to restart.

I took mine in to the Apple Store (covered with AppleCare) in the UK and they were useless. They didn't diagnose the problem even after 3 visits. They replaced the power supply on the 3rd visit after I called AppleCare. The repair technician and the genius had a disagreement that the power supply was causing the issue.

The store managed to damage the stand of the computer, and also caused chipping to the enclosure.
They replaced the stand, however managed to chip it a second time.
They also caused chipping to the enclosure but refuse to acknowledge the damage despite the computer never leaving the Apple Store.
I had a horrendous experience with one of the rudest managers I've ever spoken to who didn't care about my concerns.

Currently have the iMac at home in the box still chipped and I have no idea if the issue has been fixed.

I have a feeling you’ve been encountering the same problems as myself.

I am booked to visit Apple tomorrow because it’s still happening despite a replacement power supply unit.

Don’t know how you get on with yours but I find I can use mine for around half an hour (tops) before it goes on me.

The problem is more persistent if I ramp the display size up (so there’s more room) so I’m not sure if there’s an issue with the graphics chip OR High Sierra as it was fine with El Capitan/Sierra.

 

[MBAir2010]

when you say "i installed photoshop" what was the source, a DVD?
Since we can't install photoshop, we need the entire CS# (i have CS4 & 3)
maybe that photoshop might be funky.

 

[AndrsnH]

I have a feeling you’ve been encountering the same problems as myself.

I am booked to visit Apple tomorrow because it’s still happening despite a replacement power supply unit.

Don’t know how you get on with yours but I find I can use mine for around half an hour (tops) before it goes on me.

The problem is more persistent if I ramp the display size up (so there’s more room) so I’m not sure if there’s an issue with the graphics chip OR High Sierra as it was fine with El Capitan/Sierra.

Please let us know how you got on at the Apple Store!

I ended up making a complaint, the service has been abysmal.

The problem is completely random with mine, it happens with no warning. Can take weeks for it to happen, then it can happen ever 10 minutes. The Apple Store just don't seem to care. I'll give the display scaling a try and see what happens!

 

[iGeek2014]

Please let us know how you got on at the Apple Store!

I ended up making a complaint, the service has been abysmal.

The problem is completely random with mine, it happens with no warning. Can take weeks for it to happen, then it can happen ever 10 minutes. The Apple Store just don't seem to care. I'll give the display scaling a try and see what happens!

Unfortunately something came up so I’ve had to reschedule for next week but I’ll be sure to let you know.

Part of me feels like taking it to the Apple Store and if it continues taking it back and leaving it there.

 

[D29800]

I see your issue (which is the same as I’m having now) was reported on in 2018. Were you ever able to find a solutio?

signed,
desperate 😬

 

[Rmonster]

It's somewhat of a coincidence that I've signed on to the forums for the first time in a long while to seek advice about the same issue and the topic was at the very top of this sub-forum.

I have a late 2015 27" i7 16GB M395X 1TB SSD which has had very little use. So much so that when I came to use it properly a few years ago, it exhibited the random shut down phenomenon and instead of dealing with it there and then, I assumed that the lack of use had caused an internal batter to run down, causing the issue. Dumb, I know.

Removing the power lead for an extended time resulted in the iMac working and this reinforced my idea that using it regularly had solved the problem.

In reality, the computer still has random shutdowns which seem to be temporarily cured by removing the power lead for a good period of time. Im using the iMac to type this message having not had it plugged in for a few weeks and started in playing youtube videos constantly in fullscreen for the last 4 hours or so.

It will seem to run non-stop with power savings turned off, ie so that the screen is constantly on and doing something, it seems bulletproof like this, but if I leave it set up so that the screen shuts down after a period of time and to let the machine go into standby, then when I try to wake it, it is just completely shut down.

If I remove the power cord for 30 seconds or so, when I reboot, it sometimes just gets through to a few seconds of the boot up before switching itself off and sometimes it will run for 5 minutes before doing the same.

However, having had the machine disconnected from the mains for an extended period of time, it has run perfectly all afternoon.

I'm in the UK. If I take it to an apple store by appointment, is an initial diagnosis free? ... or does anyone have any further insight into the issues I've described.

Many thanks, Rich

 

[Rmonster]

I see your issue (which is the same as I’m having now) was reported on in 2018. Were you ever able to find a solutio?

signed,
desperate 😬

Sorry that I posted to seek help and unable to help you with your issue

 

[Rmonster]

Since having unplugged the iMac for an extended period, I plugged it back in and got a successful boot. I then ran YouTube videos continuously for 6 hours or so and then let the machine go to a screensaver but forced to remain on. It’s been running continuously for the best part of three days now. This makes me feel that there is no PSU issue as is often suspected nor a logic board issue. Any ideas, anyone... anyone ... anyone... thanks for any input