Waking Up Monitor in Close Clamshell Mode

Question

Level 1

6 points

Waking Up Monitor in Close Clamshell Mode

I recently purchased a 2016 Macbook Pro and LG monitor (27UD88-W; it's USB-C, but not one of the brand-new, designed-in-conjunction-with-Apple ones). If my MBP is open and disconnected from the display, I can plug it in and easily enter closed clamshell mode. However, once there, if I put my computer to sleep and later wake it up by, say, hitting the spacebar on my external keyboard, the monitor doesn't always get the signal that the computer is now awake (sometimes it does; sometimes it doesn't).

When I read Apple's article about using the computer in closed clamshell mode, it doesn't mention anything about being able to do this (the article always assumes that, to start, your computer is open and not connected to the monitor). Is this not supported? (I was able to do this on my old Macbook Air and Dell monitor, so it would be odd if it suddenly wasn't).

If you are supposed to be able to do this, might it be that I have a defective cable?

Thanks!

MacBook Pro with Retina display, macOS Sierra (10.12.1)

Posted on Dec 11, 2016 9:26 AM

Reply

Answer 1

May 8, 2017 4:54 AM in response to alhs77st

Hi,

Wow, I might have found someone with the same problem. After weeks of researching this online.

I seem to have the same problem with the same Setup:

* 2016 MacBook Pro 15" Radeon 460 Pro

* LG 27UD88-W

* Connected via LG's provided USB Cable

* MacBook in Clamshell mode and connected to the LG Screen

So here's my problem:

When I sent it to sleep and come back later after a day or so, when I wake the MacBook up by hitting a key on my external Apple Wireless Keyboard, the LG screen turns on, detects a video signal source, but the screen stays black and after 10 second tells me that there is no signal received and turns off again. In this situation, when I open up the MacBook lid, the screen on there also stays black, but the MacBook is actually running, because the TouchBar is on and I can blindly navigate around macOS that way.

The tough thing about this issue is, it is hardly reproducable and it happens like every second day. So I started to do some long-term troubleshooting here.

A few things I tried so far and which did not help:

* Uninstall f.lux (and its color profile). Fortunately macOS has this feature now anyway

* Update the LG firmware to 3.11 from http://www.lg.com/us/support-product/lg-27UD88-W

* Reset the SMC

* Reset the NVRAM

A few things that I want to test as next steps:

* Disable FileVault (the unlocking of the harddrive might be an issue?)

* Disable Apple Watch Auto Unlock (the unlock might interfere with the video signal handshaking?)

* Use a different color profile for the LG monitor (it might be faulty)

* Use a different USB-C Cable (the one provided by LG might have an production issue?)

* Disconnect the USB-Hub that is connected to the LG monitor (just to be sure it's not interfering either)

* Wait for the next patch updates of macOS

So, actually currently I'm on step 1 of this list (Disabled Filevault). And it's been a couple of days now since the problem occured. I'm starting to get the feeling that this could be it.

I would be very curious to know if you also have Filevault enabled by any chance?

Reply

Answer 2

Ulexes138

Community Specialist

Dec 15, 2016 5:16 PM in response to alhs77st

Hello alhs77st,

Thanks for reaching out to the Apple Support Community. I understand you've had some trouble with your external monitor when waking up your new Mac, and I'd like to help. In cases like this, it can help to reset the SMC (System Management Controller), which controls the different hardware on your Mac. Have a look at the article below to learn how to reset your SMC.

Reset the System Management Controller (SMC) on your Mac - Apple Support
If the behavior persists, or you run into any trouble we're here to help.
Best Regards.

Reply

Answer 3

alhs77st Author

Level 1

6 points

Dec 15, 2016 5:16 PM in response to Ulexes138

This seems to be working -- thanks!

Reply

Answer 4

alhs77st Author

Level 1

6 points

Dec 17, 2016 8:33 PM in response to Ulexes138

I thought this had fixed the problem, but it didn't. Any other ideas? Could it be a bad cable?

Reply

Answer 5

Dec 19, 2016 1:06 PM in response to alhs77st

I have this kind of problem too. I have the same set up as you. And I use the cable that came in with the monitor. I am wondering if there is anything I can do to fix it.

Reply

Answer 6

alhs77st Author

Level 1

6 points

Dec 19, 2016 1:26 PM in response to ethan_nie

Hi ethan_nie,

I just spoke with LG today. Since I've been able to attach my work laptop (an HP) to the monitor via Display Port and had no trouble waking/sleeping, they were thinking it was a defective cable. So they're sending me a new one. However, given your experience, I'm doubtful that's going to work.

By the way, does anyone know the exact type of cable you need to hook the MBP up to a 4K display (the included Apple USB-C doesn't work) -- is it Thunderbolt 3?

Reply

Answer 7

Dec 19, 2016 1:40 PM in response to alhs77st

I used the usb-c cable that was provided by LG. So I don't think there is anything wrong with the cable.

Reply