Yesterday everything was working fine. I had my MacBook Pro (four USB-C ports & touch bar) connected to my LG UltraFine 5K monitor (official model name: LG 27MD5KA‑B). At the end of my day's work I turned everything off. In the morning I turned everything back on but nothing seemed to work.
I proceeded to disconnect the monitor from the MBP and there the latter turned on without problem. I tried hot-plugging back the monitor and the MBP's screen turned black. Event the touch bar was unresponsive. So I tried all sorts of combinations in order to solve the problem:
- Turn off the MBP, and unplug everything from the mains, wait a moment and reconnect everything;
- MBP PRAM reset;
- MBP SMC reset;
- Removed all connected peripherals (either directly to the MBP and/or to the monitor);
- Tried all the USB-C ports of the MBP;
- Tried with another touch bar MBP;
One thing that half works is when the LG UltraFine 5K is connected to the mains and I hook an MBP with the lid close. In this case the monitor lits up, although very dimly, I can see the Apple logo and then suddenly the logo is spread horizontally across the screen and lower quarter of the screen is garbled (everything very faint). If I open the lid, only the caps lock seems to work (hinting that the computer has not crashed). If I unhook the MPB it responds without problems after a few seconds. Reconnecting it and the MBP screen turns black and the computer becomes unresponsive (apart from caps lock). I can, however, access the computer through remote login (SSH) and managed to shut it down or restart it from there (
sudo shutdown -h now or
sudo shutdown -r now).
I even downloaded the LG Screen Manager, but the app seems totally useless in my case (event the copyright notice seems strange showing "Copyright 2016-2026 LG Electronics Inc.").
Any suggestions on what to do next (apart from bringing the apparatus for repair)?
- MBP (13", 2017, 4 thunderbolt-3 ports, Intel Core i5 @ 3.1 GHz, 8GB RAM, Intel Iris Plus Graphics 650 1536 MB);
- MBP (13", 2017, 4 thunderbolt-3 ports, Intel Core i7 @ 3.5 GHz, 16GB RAM, Intel Iris Plus Graphics 650 1536 MB);
- Both MBP are installed with macOS Mojave Version 10.14.2
- LG UltraFine 5K (aka 27MD5KA‑B);