How to Tell Whether Your New LG UltraFine 5K Display Has the Shielding Fix

Last week, we shared a brief video showing that LG’s revisions to the shielding in the UltraFine 5K display have successfully addressed issues with the display flickering and disconnecting when in close proximity to Wi-Fi routers. Apple and LG had temporarily pulled the display from the market while LG adjusted its manufacturing processes to incorporate the fix and push the new stock into sales channels, and sales of the revised display began earlier this month.

At the time of last week’s post, we noted that customers purchasing the UltraFine 5K display should check for serial numbers beginning with 702 or 703, as these indicate manufacturing dates of February or March after the fix was put into place. Several MacRumors readers subsequently reported, however, that they have recently received units shipped from Apple with serial numbers starting with 612, indicating manufacturing dates in December 2016.

These readers have been uncertain as to whether their units have the revised shielding in place, or if they should be testing their displays to see if the flickering issue can be induced. One reader noticed that the label on the box of his December UltraFine 5K included a black circular sticker at the top left, a sticker that was not present on our original UltraFine 5K display that was manufactured in November and shipped in December and which was susceptible to the interference issue.

December 2016 unit retrofitted prior to sale (left) vs. March 2017 unit properly shielded from the start (right)


Newly manufactured UltraFine 5K units include a black square printed directly on the label in the same location, and LG has confirmed to MacRumors that the presence of a circle or square does in fact indicate that the unit has the revised internal shielding and should be protected from the interference issues.

While LG did not explicitly confirm any difference between a circle and a square, it appears that the square is indicative of a unit that was originally manufactured with the proper shielding, while the circle is used on earlier units that were subsequently retrofitted with the shielding before sale. There should be no difference in the performance of the two versions.

For those users with units lacking a circle or square on the label and thus susceptible to the Wi-Fi interference, LG is conducting free repairs to install the proper shielding. Users are advised to contact LG to arrange for the repair, which can take up to 7-10 business days once the display is received by the repair facility.

Customers interested in purchasing the UltraFine 5K should remember that Apple’s 25 percent discount on USB-C and Thunderbolt 3 accessories is still scheduled to end on March 31, so they have just over a week to order the display at its discounted price of $974 before it goes back up to its regular price of $1299.95. It is possible Apple could extend the discount as it has done once already, but there are no guarantees.

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Tag: LG

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This is a desk-filling display in the truest sense of the term: 37.5 inches on the diagonal with a 21:9 aspect ratio and a native resolution of 3840×1600. It has fewer pixels than a true 4K or Ultra HD display, but its sheer size makes up for it in some unique ways. While the UltraFine 5K and 27UD88 displays work best at Retina or scaled resolutions, the 38UC99 uses a full 3840×1600 desktop that leaves everything on screen at just the right size to be useful. No, it’s not a Retina display in this mode, but until we have 8K displays this will have to do.

Even without Retina resolution, this display is impressive. The sheer size of it gives you so much flexibility in terms of your workspace. I can easily have three large windows open side-by-side with room to spare.

UltraFine 5K, 38UC99, 2016 MacBook Pro (left to right)


I’ve been testing this in a three-display setup with the new 15-inch MacBook Pro, an UltraFine 5K, and the 38UC99. It’s a ridiculous amount of desktop space that I can barely fit on my desk, and the MacBook Pro with entry-level graphics runs all of it without breaking a sweat.

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LG’s UltraFine 5K Display returned to the market earlier this month after LG made some changes to the display’s shielding following the discovery that the original design left the display vulnerable to interference from Wi-Fi routers and other electronics. The issue was a bit of a black eye for Apple, considering the company recently elected to exit the display market and instead partnered with LG on the new 27-inch UltraFine 5K and its smaller sibling, the 21.5-inch UltraFine 4K.

We purchased one of the original UltraFine 5K units back in December, with our model carrying a manufacturing month of November 2016 based on its serial number. LG has now provided us with a unit manufactured last month after the design revisions were put in place, and we’ve had a few days to compare the performance of the two units in the presence of Wi-Fi routers.



In day-to-day usage, we failed to see any issues with the original model, even with an AirPort Time Capsule located just three feet from the display, inside the two-meter radius LG recommended users should keep as a minimum once the company discovered the issue.

We were, however, able to induce the issue in the unit by bringing another Time Capsule into very close proximity with the rear of the display, causing it to flicker and disconnect from the host computer. The display sometimes reconnected to the computer on its own once the interference was removed, but other times it required that the Thunderbolt 3 cable be briefly unplugged or even the entire UltraFine 5K be power cycled before it would reconnect.

With the revised UltraFine 5K Display in hand, we’ve been able to subject both displays to side-by-side testing that confirms the issue has been successfully addressed. While the issue is easily reproducible on the original model as long as the Wi-Fi router is in close enough proximity, we were unable to recreate the issue on the revised model despite extensive efforts.



With Apple once again shipping the UltraFine 5K Display, new orders are currently showing in-stock availability in Apple’s U.S. online store, although Personal Pickup remains unavailable.

Apple’s discounted pricing on the display of $974 is scheduled to run through the end of this month, at which time the display will return to its normal $1299.95 price. Apple already extended its discounted pricing on USB-C and Thunderbolt 3 accessories once and it’s possible the promotion could again be extended, but for those who want to make sure they receive the discounted pricing, they should be sure to order by March 31.

Customers purchasing the UltraFine 5K Display, regardless of what vendor they use, should make sure they are receiving revised units to ensure they are protected from the Wi-Fi interference issue. The first three digits of the display’s serial number (visible on the exterior of the box) correspond to the last digit of the year and the two-digit month of manufacture, so buyers should look for serial numbers starting with 702 or 703.

Those who purchased earlier units may be eligible for repairs if their units are exhibiting the interference issue, and affected customers should contact LG or Apple for information on repair procedures.

We’ve arranged for a repair of our affected unit through the live chat option. Once the repair request is initiated it can take a day or two to receive a shipping label and repair details, and LG tells us it can take up to 7-10 business days for the actual repair once the display has been received at the service facility.

Related Roundup: Displays
Tag: LG

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