Member Avatar for Dani

I have a late 2016 MacBook Pro running the latest version of OS X Sierra 10.12.6

Ever since I got it, I've been having a problem connecting it to external displays.

Firstly, there is the 32" 4K Seiki Pro, connected via a USB-C cable. Most times when the Mac goes to sleep, the display does not come back until I put the computer back to sleep and wake it up, and then connect the cable when it's woken. Apple Support says this is a known bug but there is not currently a fix.

Then there is the LG UltraFine 5K 27" display for Mac, connected via the included Thunderbolt 3 cable. I got it today. It starts out flickery (the best way to describe it is what an old CRT monitor looks like). But then it looks like it's having a seizure, garbling up pictures and random colors and flickering super bad, and being completely chaotic. I'll try to attach a video to better explain. If the Seiki is connected as well, both monitors do the same thing as long as the LG is connected.

  • 4 Contributors
  • 3 Replies
  • 477 Views
  • 13 Hours Discussion Span
  • Latest Post Latest Post by rproffitt

Dani AI

Generated

Short practical summary and checklist (answers , , )

The LG UltraFine 5K is a Thunderbolt‑3 display and needs a proper Thunderbolt‑3 (not a USB‑C-only) connection and a full‑speed TB3 cable to run at 5K; weak/incorrect cables or a faulty TB3 lead commonly produce the CRT‑like flicker and corruption you describe. (lg.com)

Step‑by‑step troubleshooting (do these in order)

  1. Isolate the problem. Disconnect the Seiki and test the LG alone to confirm the LG is the trigger.
  2. Swap the cable. Try a known‑good Thunderbolt‑3 40Gb/s cable (Apple’s TB3 cable or a reputable Thunderbolt‑certified 0.8m cable). A USB‑C charge/data cable will often look right but won’t carry the full 5K video stream. (plugable.com)
  3. Update the display firmware. Install LG’s “LG Screen Manager” on macOS and run the monitor firmware update while the LG is connected and awake — many users fixed similar glitches this way. (macrumors.com)
  4. Standard macOS checks: install available macOS updates, use Displays → hold Option → “Detect Displays”, and try Reset SMC / Reset NVRAM (for Intel Macs) as Apple documents for display problems. If the LG only misbehaves on your machine, test it on another Mac to rule out the Mac as the cause. (support.apple.com)
  5. Consider RF/shielding issues. Some LG units required improved shielding because strong nearby Wi‑Fi / cellular sources can induce disconnects/garbling; if symptoms only occur in a specific location, try moving Wi‑Fi gear or testing the monitor in another room. If shielding/repair is needed contact LG support. (appleinsider.com)

Notes and cautions

  • Because the 2016 MBP + Sierra era had known display bugs, make software updates a priority before hardware RMA. (support.apple.com)
  • If a different TB3 cable and the firmware update don’t stop the corruption, the monitor’s Thunderbolt controller or internal shielding may be defective — that typically needs LG service or replacement. (appleinsider.com)

Useful links

If the above steps (known‑good TB3 cable + LG firmware + macOS updates / SMC/NVRAM reset) don’t stop the seizure‑like corruption, the next practical move is an RMA/repair request to LG — the symptoms you describe match known HW/firmware/shielding failure modes. (appleinsider.com)

Recommended Answers

All 3 Replies

Member Avatar for pty

Are you definitely using a Thunderbolt 3 cable between your MBP and the 5K monitor?

Incidentally, slightly jealous, I need to get one of those monitors but I'm worried my 2013 MBP might not be beefy enough to drive it smoothly.

Member Avatar for rubberman

You say you are using the cable that came with the display? Have you tried an "official" Apple cable? It is possible that your cable is defective.

Member Avatar for rproffitt

So I went looking for this LG and at the Apple site read the reviews at https://www.apple.com/shop/product/HKN62LL/A/lg-ultrafine-5k-display

That was not a happy reading. But did confirm a few things. One, you're not alone in seeing product issues and most of all, the display may have firmware. So that's my input here.

See if the display has a firmware update.

Be a part of the DaniWeb community

We're a friendly, industry-focused community of developers, IT pros, digital marketers, and technology enthusiasts meeting, networking, learning, and sharing knowledge.