LG Ultrafine 5k 27MD5KA-B

Display model

This model seems to have a prone-to-dying Texas Instruments USB-C PD + Thunderbolt multiplexer controller "TPS65983" as ive seen two (suspecting 3) models with it being the cause of the display not working. Issue can stem from other places as well, like power supply (fuses etc).

Issue	Possible solutions	References / media
Intermittent disconnecting/reconnecting from device sleep. Testmode works (see bottom of page) Display does not wake up but does charge connected device. Testmode works (see bottom of page)	(On models produced before the year 2017) LG claims RF interference, try moving display away from routers, or routers away from the display. On models manufactured after 2017 LG claims sufficient shielding has been implemented, this has seemingly not worked well. Test different thunderbolt 3 cables for connecting the device to the displays main port. The cable that came with the monitor is the best candidate Test unplugging device for 10 minutes from power then replugging it. Some people have reported loose Thunderbolt port, the main one. Resoldering might be needed.	https://bit-tech.net/news/tech/monitors/lg-faulty-ultrafine-5k-monitors/1/
Display is 100% unresponsive, does not charge connected device. Testmode works (see bottom of page)	Test different thunderbolt 3 cables for connecting the device to the displays main thunderbolt port. The cable that came with the monitor is the best candidate Test unplugging device for 10 minutes from power then replugging it. Disassemble the monitor and unscrew the main board and inspect the TPS65983BA chip located on the same side as the USB-C ports, if there are any visible indications of damage a replacement might be necessary. The chip can be replaced with an (almost) identical TPS65983BA (TPS65983BAZBHR) Datasheet, I bought them on Mouser. It is the same BGA layout as CD3215 chips commonly found in more modern Macbooks, seemingly called both "BGA MicroStar Junior (96)" and "NFBGA (96)". The chips should come pre-balled (mine from Mouser did) so it's a quite easy repair if you have worked with BGA before. It is not sure if the replacement chip will exhibit the same behavior after some time, this has not been documented.	Frontside of board, destroyed TPS65983 Backside of board, charred components and layers
Display is 100% unresponsive, testmode doesnt work (see bottom of page)	Suspected faulty power supply. Disassemble monitor and unscrew power supply, making sure to be careful with components such as capacitors which can hold charge for a substantial amount of time after being unplugged, make sure to touch the board holding only the edges. Check the two fuses for continuity, replace if needed Check capacitors for swollen tops Check for any charred or miscolored components The power supply board is possible to buy online if needed ->	https://www.ebay.com/p/7031234791 https://www.ebay.com/itm/225028024101 https://www.aliexpress.com/item/1005004728716386.html

How to use testmode:

• 

  Location of the button, make sure power is plugged in while testing. 1. powerplug 2. testmode button

• 

  What the display should show if testmode works

External references and other people having issues:

People complaining about loose main port: https://maker.pro/forums/threads/lg-ultrafine-27md5ka-b-provides-power-to-laptop-but-does-not-get-detected-by-computer-no-video.292861/

Cable issues: https://discussions.apple.com/thread/252555535

Francis (Francis#2054 on discord): These are my own observations, but a quick google shows others having similar issues.

I have had 3 identical models in for "not starting".

Display 1: Testmode works, fixed by replacing TPS65983

Display 2: Testmode works, replacing TPS65983 has not fixed it

Display 3: Testmode does not work, fuse "F100" faulty, not fixed yet (Jan 30, 2023)