LG 38UC99-W does not display via USB-C

Discussion in 'MacBook Pro' started by typecomp, Nov 28, 2016.

  1. typecomp, Nov 28, 2016
    Last edited: Nov 28, 2016

    typecomp macrumors newbie

    Nov 28, 2016
    Heads up to anyone who got a 2016 MacBook Pro and was thinking of connecting via USB-C port to the new LG 38UC99-W. It does not display any image despite being able to power the MacBook and have connected drives appear on the MacBook desktop. Just a black screen. LG offered no solution and simply said it should work via USB-C port. I was able to get the LG to display when using a display cable and USB-C to DisplayPort adapter. The adapter which shall remain nameless barely accomplished the job and the slightest of movement of the cable resulted in loss of display. I also a experienced a complete freeze of the MacBook while connected to the LG. I tried out a few different 34 inch LG models and concluded that a resolution of 3440 x 1400 has an appearance similar to that of my 8 year old Cinema Display. Given this experience I will not be gambling on the plastic, clunky looking LG 4k & 5k displays that are supposedly "made for the mac".
  2. RyanC1384 macrumors newbie

    Nov 24, 2016
    I just ordered this monitor and have heard from others that it works fine. Have you done any troubleshooting?
  3. typecomp, Nov 28, 2016
    Last edited: Nov 28, 2016

    typecomp thread starter macrumors newbie

    Nov 28, 2016
    None was suggested by LG and I returned the monitor. Don't know what to troubleshoot on two new pieces of equipment other than getting another new cable. I am returning the MacBook Pro since no one else makes an ultra wide monitor with C port. Hope yours works. I am going to wait for next update to 5k iMac and get that since sharp text has new appeal after my experiences with LG ultrawides. I also found that having only two inbound USB ports on the monitor is a pain.
  4. Pootmatoot macrumors 6502a

    Nov 17, 2014
    Are you using a "proper" USB-C cable and not the charging cable that came with the Mac? That won't have the bandwidth.
  5. typecomp thread starter macrumors newbie

    Nov 28, 2016
    No sure wasn't and no one at Apple, LG, or Micro Center suggested this was the problem. You would think Apple would have released that information sooner than 11 days ago. They are still telling people that Cinema Displays with mini display port connectors can be used on the new MBP via T3-T2 connector. Which it can't. And, as I just found out as I am writing this, Apple is still telling people their charge cable can connect to monitors for display purposes.

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  6. Pootmatoot macrumors 6502a

    Nov 17, 2014
    It might not be the case - I've not used that specific monitor - I just know it's certainly an issue with similar devices.

    Welcome to the world of USB-C! The water's warm! And chaotic!
  7. typecomp thread starter macrumors newbie

    Nov 28, 2016
    Thanks for the welcome but I am leaving C-world and will be looking forward to an iMac when they revamp those.
  8. Pootmatoot macrumors 6502a

    Nov 17, 2014
    Heh, I won't be buying a USB-C only device for many years, I suspect. Apple have lost me this cycle: I'll be getting an XPS when they refresh in January.
  9. Pbrutto macrumors 6502a


    Apr 21, 2015
    Eastern PA
    Is it a 13 or a 15? If it's a 13 you may have to plug it in the left ports only for it to work....
  10. RyanC1384 macrumors newbie

    Nov 24, 2016
    This could be the case, I have read that 2 of the USB-C ports on the 13" MacBook Pro with Touch Bar are not as fast as the other two.

    I understand your frustration, but it sounds to me like you've thrown in the towel a bit prematurely.
  11. typecomp thread starter macrumors newbie

    Nov 28, 2016
    Yes I regret not trying LGs cable which would have solved the problem. On the other hand I now realize that I value resolution over screen real estate and believe I will apreciate a 5k monitor over an ultra wide.
  12. Kiddomac macrumors newbie

    Jan 3, 2017
    i had the same problem at first, but then somehow it upgraded to flickering picture. i tested around for 2 hours or so getting increasingly frustrated, now i have a stable 60 Hz picture with the lg usb-c cable. the trick was to also connect the macbook to an outlet, as far as i can tell.

    can anyone here confirm this?
  13. AlpineAddict macrumors newbie

    Aug 16, 2017
    Hi Folks...
    Ive just caught up with this thread, as I'm having similar difficulties with connectivity of the LG 38" monitor and my 2017 MacBook Pro. I have used the USB C cable, supplied with LG monitor, direct to the MBP and it seems to work ok, BUT the cable supplied with the MBP does NOT work... Haven't checked the theory of 2 ports on one side being faster then the other 2 ports... However, I want hard wired internet, so I bought a dock (Belkin Thunderbolt 3 express dock).

    This dock 'should' work with all monitors. I have plugged MBP to dock with LG supplied USB C lead, and dock to Monitor with Belkin USB C lead... The monitor does NOT work, at all... it actually renders the whole dock inactive and shuts it down to standby...

    I then tried connecting the Monitor to the dock with LG supplied DisplayPort lead, and then dock to MBP with LG Supplied USB C lead and all is good in the hood...

    I called Belkin to find out why the USB C lead would not work for all connectivity and they said, after looking at the tech spec for the LG monitor, that the USB C port on the monitor is not an 'actual' USB C port for purposes of connecting to, like I was, and that it was purely for charging etc. ... Funny as it worked before when I had the MBP direct to the monitor...!!!!!! They said the port did not have enough transfer speed...?????? Not sure I believe that tbh...

    I know very little about this, but am desperate to find out why I can't use USB C from the screen to the dock...

    I have today sent the dock back, as it could be faulty (due to it not detecting speakers at all, via either of the audio ports)... I am waiting for a replacement, next week, so I'll see what the outcome is...

    I'd also be interested to know (from anyone with this screen) if it's possible to connect an ethernet cable, via an adapter, through the monitor to get hard wired internet... Would save me £300 on the bloody dock...!!!

    Thx y'all...
  14. Claywd macrumors newbie

    Nov 9, 2012
    That got me thinking.... so I tried it out and yeah it works. I actually hooked up the startech usb.30 hub that includes an ethernet adapter and two usb3.0 ports. got like $20. pretty sweet now that my monitor is a dock. :)
  15. Claytonious macrumors newbie


    Aug 2, 2018
    I just got this working correctly with a 15" Macbook Pro 2017 with touchbar. It wasn't working for quite a while, but simply plugging the USB-C cable into a different port on the MBP made the beautiful image suddenly appear on the monitor and now all's well. I *am* using the included, provided cable from LG that came with the monitor.

    It's also powering the MBP just by being plugged into the display.

    Good stuff.
  16. insats macrumors newbie


    Oct 9, 2018
    A little late to the party here, but I'm looking to buy the LG 34UC99-W to use with my 12" MB (2017).

    1. Will I need another USB-C cable than the one that came with the charger (as mentioned elsewhere here)?
    2. If so, how do I know which type of USB-C cable to get? There seems to be a lot of different types
    3. Will the Macbook charge while connected to the monitor?

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