my mac does not like external monitors

[thefriendshipmachine]

hello friends

I have a 2014 imac and an asus 4k monitor and I updated to sierra. Now when I put the mac to sleep and wake it up, it gives me a black screen only and I have to reboot it. This only happens when my external monitor is plugged in.

I really want to go back to el capitan but my time machine hard drive has broken

 

[nambuccaheadsau]

Two thoughts. Any chance you are running FileVault to encrypt?

Maybe try turning off hibernation via Terminal. Here is a link on these issues:-




https://www.macissues.com/2015/05/08/how-to-fix-your-mac-not-waking-from-sleep/

 

[DeltaMac]

Black screen on the Asus monitor only, or black on both displays?
Can you sleep your iMac, wake it up, then reseat the video plug to get the Asus to come on without restarting your iMac?
(This is NOT a solution, just troubleshooting to see if that will help )

What connection are you using from the iMac to the Asus?
Thunderbolt to DisplayPort?
Thunderbolt to HDMI?
Something else?

 

[Stefan johansson]

Strange. Of course,I know a MacBook is different,but I connected mine to various monitors,TV sets and projectors withouth problems. For my connection,I use HDMI,or sometimes,on older TV sets,S-video with an adapter.

 

[Fishrrman]

You can go back to El Cap if you want.
But it involves work.

How to do it (non-detailed version)
1. Download CarbonCopyCloner and clone your existing internal drive to an external drive
2. Create a bootable El Capitan USB flash drive installer
3. Boot from the El Cap USB flash drive.
4. Re-initialize internal drive
5. Install El Cap onto it.
6. Create new account
7. Connect cloned backup, use get info to ignore permissions.
8. Manually copy stuff back to your internal drive (tedious process).

That will get you there.
Plan on most of a day to get it done.

 

[thefriendshipmachine]

Strange. Of course,I know a MacBook is different,but I connected mine to various monitors,TV sets and projectors withouth problems. For my connection,I use HDMI,or sometimes,on older TV sets,S-video with an adapter.

yes, my macbook love sierra but its just my imac which does it

Black screen on the Asus monitor only, or black on both displays?
Can you sleep your iMac, wake it up, then reseat the video plug to get the Asus to come on without restarting your iMac?
(This is NOT a solution, just troubleshooting to see if that will help )

What connection are you using from the iMac to the Asus?
Thunderbolt to DisplayPort?
Thunderbolt to HDMI?
Something else?

both become black. Not off black but the pixels are activated but just on the color black. Sometimes I see dark flashes of green too but this is rare. It is displayport 1.2 and its an ASUS PB287 monitor.

Sometimes unplugging the monitor before sleeping works but sometimes not. I dont understand how this can be but normally I have to reboot it to fix it.

Two thoughts. Any chance you are running FileVault to encrypt?

Maybe try turning off hibernation via Terminal. Here is a link on these issues:-

https://www.macissues.com/2015/05/08/how-to-fix-your-mac-not-waking-from-sleep/

I turned these off and sadly the problem still happens but thank you for these suggestions because they make sense to try!
[doublepost=1492564322][/doublepost]I have googled the bug and it looks like people with imacs and dell 4k monitors have the same problem!

https://discussions.apple.com/thread/7906502?start=0&tstart=0