MacBook Pro 15’ 2018 + LG 43UN700-B 43" 4K USB-C Display Not Working

[techguy500]

Greetings MR!

Hopefully someone can help me out here with the issue that I’m having. Below is what's being used at the moment:

• MacBook Pro 15 (Mid 2018)
• Monoprice Thunderbolt 3 (40 Gbps) USB-C Cable, 100W, 2.0m (CHARGES SUCCESSFULLY, BUT NO DISPLAY)
  
  Products no longer Available
• StarTech Thunderbolt 3 Cable - 2m, 20 Gbit/s, USB-C (CHARGES AND DISPLAYS SUCCESSFULLY)
  
  

  Thunderbolt 3 (20Gbps) USB-C Cable, 2 m | Thunderbolt Cables | StarTech.com

  Provide twice the data transfer speed of any other cable type, enable full 4K 60Hz video, and power your devices with a single cable

  www.startech.com
• LG 43UN700-B 43" 4K
  

  43” 4K UHD IPS USB-C HDR 10 Monitor - 43UN700-B | LG USA

  Discover the 43” 4K UHD IPS USB-C HDR 10 Monitor that features USB-C with 60W PD and 4 x HDMI Input. Find reviews, specs, and more for 43UN700-B.

  www.lg.com
  • 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

For some reason the Monoprice cable isn’t picking up USB-C display from the LG monitor while connected to the MacBook Pro 15' 2018. I’ve tried to “detect displays” but that doesn’t help. The StarTech cable displays the MacBook Pro 15' 2018 while connected to the LG's monitor USB-C port successfully with no problem.

However, my MacBook Pro 15' 2018 is picking up the charging signal from the LG monitor while using both the Monoprice and StarTech cables.

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!

 

[gjesp]

It is a known issue, and has nothing to do with the brand of the cable, but the TB3 version of it. You have to use a 20 Gbit/s TB3 cable, as the newer 40 Gbit/s ones do not work as you would expect. The older model 43ud79-b also have the same limitation. I suspect it's because the 40 Gbit/s port are more expensive, so they settled on 20 Gbit/s port to bring the cost down. As for performance (for this monitor) there is 0 practical difference between the two

 

[techguy500]

It is a known issue, and has nothing to do with the brand of the cable, but the TB3 version of it. You have to use a 20 Gbit/s TB3 cable, as the newer 40 Gbit/s ones does not work as you would suspect. The older model 43ud79-b also have the same limitation. I reckon it's because the 40 Gbit/s port are more expensive, so they settled on 20 Gbit/s port to bring the cost down. As for performance, there is 0 practical difference between them two.

What’s the reason behind that? If you don’t mind sharing.

 

[CheesePuff]

What’s the reason behind that? If you don’t mind sharing.

Well he mentioned most likely due to the additional cost for a 40 Gbps port vs 20.

 

[gjesp]

Yes, that is what I meant

 

[Newton Le]

@techguy500 have you had any other issues with this monitor? I have it connected to a 2019 Macbook Pro 15 and when it wakes from sleep, the colors are all washed out. It comes back after a cable disconnect/reconnect or a monitor power cycle, but having to do this every time is annoying.

 

[gjesp]

@techguy500 have you had any other issues with this monitor? I have it connected to a 2019 Macbook Pro 15 and when it wakes from sleep, the colors are all washed out. It comes back after a cable disconnect/reconnect or a monitor power cycle, but having to do this every time is annoying.

Have you tried disabling the HDR feature in MacOS and if possible from the monitor OSD

 

[DannyJohnLaw]

@techguy

What’s the reason behind that? If you don’t mind sharing.

Greetings MR!

Hopefully someone can help me out here with the issue that I’m having. Below is what's being used at the moment:

• MacBook Pro 15 (Mid 2018)
• Monoprice Thunderbolt 3 (40 Gbps) USB-C Cable, 100W, 2.0m (CHARGES SUCCESSFULLY, BUT NO DISPLAY)
  
  Products no longer Available
• StarTech Thunderbolt 3 Cable - 2m, 20 Gbit/s, USB-C (CHARGES AND DISPLAYS SUCCESSFULLY)
  
  

  Thunderbolt 3 (20Gbps) USB-C Cable, 2 m | Thunderbolt Cables | StarTech.com

  Provide twice the data transfer speed of any other cable type, enable full 4K 60Hz video, and power your devices with a single cable

  www.startech.com
• LG 43UN700-B 43" 4K
  

  43” 4K UHD IPS USB-C HDR 10 Monitor - 43UN700-B | LG USA

  Discover the 43” 4K UHD IPS USB-C HDR 10 Monitor that features USB-C with 60W PD and 4 x HDMI Input. Find reviews, specs, and more for 43UN700-B.

  www.lg.com
  • 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

For some reason the Monoprice cable isn’t picking up USB-C display from the LG monitor while connected to the MacBook Pro 15' 2018. I’ve tried to “detect displays” but that doesn’t help. The StarTech cable displays the MacBook Pro 15' 2018 while connected to the LG's monitor USB-C port successfully with no problem.

However, my MacBook Pro 15' 2018 is picking up the charging signal from the LG monitor while using both the Monoprice and StarTech cables.

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!

I just got the 43un700 and the usb c cable that came in the box doesn’t charge or send a video signal. Did you find a cable that worked?

 

[TJ82]

I just got this 43UN700 monitor yesterday and it's been a disaster. Some cables I use will only let me use 720p resolution!

Even the cable that came in the box is showing 800 x 600 resolution as the only option.

Also changes depending on which port on the MacBook Pro I use.

(MacBook Pro (16-inch, 2019)

How can I get 4K from MacBook Pro to the monitor, any ideas? Surely the cable that came in the box would be fine?

Ordered in this Belkin, but by reading the comments, it seems it's a bad choice: https://www.amazon.co.uk/gp/product/B073KCPS2M/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&th=1

Should I be looking for a 20 GBPS USB-C cable? Anything you can recommend which worked?

 

[peta909]

I have a mpb 16" 2019 w OSX 11.4. To get it to work w LG 43UN700 monitor. I used a spare USB C cable (labelled USB C Type 1 5A). SOrry, i have no idea where I bought the cable from. I also had to connect it to the lower left hand (I was facing the screen with its screen is opened) TB3 port.

It's frustrating dealing with TB3 vs USB C standards...

 

[TJ82]

My setup is now working. Looks like Apple stealth patched it in one of the a recent updates. Works with any cable and any port now.

Headache over!

 

[simohell]

Hi,

The usb-c cable that came with the monitor didn't work on my 2021 M1 Macbook Air or the 2019 16" macbook pro, but it charged both.

Using the cable form my older LG monitor it worked just fine as expected with the M1. The 16" only had the 720p option, but i hope this is fixed with software update (no issues with older LG 27" 4K monitor)

I found a spare USB-C cable form my Lacie external hard drive. It's a USB 3.1 SS 10GBS, and it worked just fine with the M1.

I can't get my head around the fact the default cable didn't work...

Any ideas? Can't image the cable being a thunderbolt 3 40gbs if the port on the display isn't TB3...
The cable does work with my Lacie external hard drive...

My thinking is the delivered cable is 5gbs and that it's not enough to run an external monitor.