Macbook Pro 2017 - USB-C Monitor not working

NielsO

macrumors newbie
Original poster
Jul 28, 2017
17
4
Hi Guys,

My Macbook Pro from 2017 does not recognize the new LG 43UD79-B. I connected the display with a new Caldigit Thunderbolt 3 cable. My macbook does recognize that there is a display connected some how. But in system information I can only see that my MB is powered with only 7 watts.... Normally the display would power 60watts.

I can't find the solution and it would be great if you guys could help me out.

I will add a couple of screen shots so you can see what my MB does.

Schermafbeelding 2017-08-08 om 12.32.02.png
Schermafbeelding 2017-08-08 om 12.33.01.png
Schermafbeelding 2017-08-08 om 12.34.09.png


Thanks!
 

JohnnyGo

macrumors 6502a
Sep 9, 2009
674
383
It seems to me that the issue is with your Thunderbolt dock. Most docks do not charge at 60-87 watts (MBP 13-15”) but rather at 30-45 watts.

But your info regarding charging with 6-7 watts may be a “net charge”, meaning the TB3 dock my be charging at 15-30watts and your Macbook is using 10-20watts.
 
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Brookzy

macrumors 601
May 30, 2010
4,778
4,813
UK
It’s probably the cable.

Thunderbolt 3 cables longer than 0.5 metres do not have full USB compatibility.

Try the cable that came with the display or another 5 or 10 Gbps USB-C cable (not the 480 Mbps charging cable that came with your MacBook).
 
Comment

NielsO

macrumors newbie
Original poster
Jul 28, 2017
17
4
Could it be that the cable must support USB 3.1/3.0 backwards compatibility? Could this solve the problem?
I am willing to send the cable back and buy a new one. But if I would buy a new one I have to be sure that it will work.
 
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brazosdog02

macrumors newbie
Sep 17, 2014
17
1
ANy luck with this? I have the same monitor and Macbook Pro. When I plug the macbook into the monitor using the proper USBC to USBC cable, no display is shown or recognized by either macbook or monitor.

I don't want to use adapters or HDMI. I want to use USBC, but apparantly, this function is not available, which seems kinda goofy.
 
Comment

Samuelsan2001

macrumors 604
Oct 24, 2013
7,694
2,118
ANy luck with this? I have the same monitor and Macbook Pro. When I plug the macbook into the monitor using the proper USBC to USBC cable, no display is shown or recognized by either macbook or monitor.

I don't want to use adapters or HDMI. I want to use USBC, but apparantly, this function is not available, which seems kinda goofy.
USB c to USB c will not work your screen has a usb c for peripherals and hard drives etc, not video input you need a usb c to display port cable. Something like this

https://www.amazon.co.uk/dp/B01LYD2Y19?gclid=EAIaIQobChMIrZydsILz2AIVBYuyCh0-OwQcEAAYASAAEgLkmPD_BwE
 
Comment

planetf1

macrumors 6502
Aug 8, 2014
392
133
Hampshire, UK
I have a MBP 2016 15 TB. The LG 27UD88 works fine over USB-C for 4K display output & power, plus the downstream USB devices connected to monitor work at USB-2 speeds. I used the cable LG supplied with the monitor. Did LG supply one with this monitor? Does sound odd it doesn't work. USB-C is connected directly not via hub?
 
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brazosdog02

macrumors newbie
Sep 17, 2014
17
1
It works, but the only way it works is if you plug everything in and then unplug and replug the usbc at the monitor. Otherwise, it won't sense the signal.
 
Comment

andy9l

macrumors 68000
Aug 31, 2009
1,697
364
England, UK
USB c to USB c will not work your screen has a usb c for peripherals and hard drives etc, not video input you need a usb c to display port cable. Something like this
If he has the 43UD79, it should accept USB-C for 4K video, data and 60W charging.

It works, but the only way it works is if you plug everything in and then unplug and replug the usbc at the monitor. Otherwise, it won't sense the signal.
This sounds stupid, but try swapping ends of the LG USB-C cable - i.e. put the end currently in your Mac into the monitor, and vice versa.

I also have a 27UD88 and when doing my research I remember reading that a number of people found this to fix a number of issues they had with Macs. It doesn't make any sense, I know - but try it.
 
Comment

brazosdog02

macrumors newbie
Sep 17, 2014
17
1
If he has the 43UD79, it should accept USB-C for 4K video, data and 60W charging.



This sounds stupid, but try swapping ends of the LG USB-C cable - i.e. put the end currently in your Mac into the monitor, and vice versa.

I also have a 27UD88 and when doing my research I remember reading that a number of people found this to fix a number of issues they had with Macs. It doesn't make any sense, I know - but try it.

That DOES sound stupid, but I've fixed issues with dumber ideas. I'll give it a go!
 
Comment

brazosdog02

macrumors newbie
Sep 17, 2014
17
1
If he has the 43UD79, it should accept USB-C for 4K video, data and 60W charging.



This sounds stupid, but try swapping ends of the LG USB-C cable - i.e. put the end currently in your Mac into the monitor, and vice versa.

I also have a 27UD88 and when doing my research I remember reading that a number of people found this to fix a number of issues they had with Macs. It doesn't make any sense, I know - but try it.
You nailed it. This cable does work, but only one way. That can't be normal. Found another cable that works both ways. So wierd.
 
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brazosdog02

macrumors newbie
Sep 17, 2014
17
1
Haha, brilliant! Can't believe that's a thing.
It makes no scientific sense to me. Its a ***** wire. How does it's direction matter?!
Haha, brilliant! Can't believe that's a thing.
Im being told by manufacturers that if the cables are being that fickle that the port on my devices is faulty. Thoughts? Is that possible if I find cables that work fine?
 
Comment

andy9l

macrumors 68000
Aug 31, 2009
1,697
364
England, UK
Im being told by manufacturers that if the cables are being that fickle that the port on my devices is faulty. Thoughts? Is that possible if I find cables that work fine?
I doubt it’s the ports. Cheap/dodgy cable manufacturers more likely to be at fault. There’s all sorts of issues with USB-C and Thunderbolt cables and docks at the moment.
 
Comment

brazosdog02

macrumors newbie
Sep 17, 2014
17
1
I couldn't get it to easily work again this afternoon. It took a bit of fiddling with and swapping cables before it finally kicked in again. I think the technology just still really sucks. For the Macbook Pro and this Monitor, it's pretty much a terrible combination if you want to use your laptop and NOT have it plugged in. When you plug in this monitor to the macbook via USB-C (without your brick charger plugged in), the macbook dings because its getting juice, but it will not pass a video signal back to the monitor and its not enough to actually charge. I don't know why this feature is built into the USB-C and Macbook to act like that but it really blows. Not sure how people actually utilize the cable when its the only thing plugged in.

Is there a way to make the freakin mac 'force' video through the cable or refresh the ports or something so that you can again get a signal through the cable? Why is this so hard? WHy can't the Mac handle this? It's supposed to be built in and all fancy and stuff...kinda expect more from a 4k freakin laptop.
 
Comment

techguy500

macrumors newbie
Aug 29, 2018
12
2
I’m having the same issue. The Thunderbolt 3 usb c cord (below) isn’t picking up display for the monitor (below) while connected to my MacBook 2015. However, my MacBook Pro 15 is picking up the charging signal from the monitor via the Monoprice cable. This is my second cable from Monoprice as I sent it back and was sent a new one because I thought that due to it not picking up the display it was a bad cord. Any advice would be appreciated. Thanks!

-MacBook Pro 15 2018
-Monoprice Thunderbolt 3 (40 Gbps) USB-C Cable, 100W, 2.0m
-LG 43UN700-B 43" 4K
  • 43” UHD (3840 x 2160) IPS Display
  • USB-C with 60W PD
  • HDR 10
  • 4 x HDMI Input
  • Multi-Tasking – PBP/PIP
  • 10W x 2ch Built-in Speakers
 
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