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Connectivity issues using a USB-C monitor with MacOS
 

Connectivity issues using a USB-C monitor with MacOS  

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motoic
(@tsh3721)
Trusted Member
Joined: 3 years ago
 

I have an LG 32UD99-W monitor which provides both USB-C and power over that same USB cable (laptop recharging). I'm connecting it in MacOS directly to my computer (not using an eGPU at all). On the back of the monitor, I decided to use the extra expansions slots to velcro an external hard drive to it (this will become important later). At first I was using the USB-C cable provided by the monitor to connect to my 2018 Macbook pro. Throughout the day after sleeping my macbook, and reopening it multiple times, the monitor would either lose the ability to connect to the Macbook or after connection it would go into a loop where it was trying to display the graphics but it would go into a loop and send them back to my notebook screen. The thing was, I realized this only started happening when I attached an external hard drive to the back of the monitor. I had heard about bad USB-C cables having throughput issues before. So I ordered an Apple 0.8m Thunderbolt 3 cable. At first it seemed like the new cable had solved the issue of MacOS not recognizing the monitor. The connection would happen quicker, so like after I plugged in the connector, the image would transfer to the monitor much faster than before when it seemed like it would struggle. But then not only did the same issue happen, it's even worse now because the monitor forgets how to connect to the machine completely and I need to restart MacOS and disconnect monitor from power to be able to connect to the monitor again. So I think the Thunderbolt 3 cable made the problem even worse. I think I am  going to experiment by just disconnecting the external hard drive from the back of the monitor. Does anyone have any experience with these issues? Could it be that the monitor itself is defective? This is a $1000 high end monitor, so I'd be surprised.

Here are the specs of the monitor: 

Screen Shot 2019 08 09 at 12.03.29 PM
This topic was modified 4 months ago

2018 15" MBP w/ Radeon Pro 560x
Nvidia GTX 1070
Akitio Node
32" LG 32UD99-W at 4k
macOS Mojave, Bootcamp Windows 10


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joevt
(@joevt)
Prominent Member
Joined: 2 years ago
 

@tsh3721

The LG 32UD99-W is not a Thunderbolt display so an active Thunderbolt 3 cable should not have worked at all.
https://9to5mac.com/2018/08/23/back-to-the-mac-011-are-longer-thunderbolt-3-cables-slower-video/

I think the Apple Thunderbolt 3 (USB‑C) Cable (0.8 m) is more appropriate.
I can't find an Apple 2M Thunderbolt 3 cable. Do you mean Belkin?

Maybe the USB signal of the external hard drive is causing interference? Maybe better cables or more distance from the display will help.

Mac mini (2018), Mac Pro (Early 2008), MacBook Pro (Retina, 15-inch, Mid 2015), GA-Z170X-Gaming 7, Sapphire Pulse Radeon RX 580 8GB GDDR5, Sonnet Echo Express III-D, Trebleet Thunderbolt 3 to NVMe M.2 case


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motoic
(@tsh3721)
Trusted Member
Joined: 3 years ago
 

@joevt

Most websites say that the cables are interchangeable! You're right that it's the 0.8m cord and I've updated my post.

2018 15" MBP w/ Radeon Pro 560x
Nvidia GTX 1070
Akitio Node
32" LG 32UD99-W at 4k
macOS Mojave, Bootcamp Windows 10


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