Question 1

colors look washed out and weird on the usb-c connection compared to hdmi from the same laptop.

Accepted Answer

DIAGNOSIS The USB-C input is likely defaulting to a limited color range (16-235) while your HDMI is set to full range (0-255). This crushes black and white detail, making everything look flat and washed out. FIX First, on the monitor itself, open the OSD with the joystick. Go to Picture Adjust -> HDMI/Input Icon (make sure USB-C is selected) -> Black Level. Set it to 'High' for full range. Then, on your computer (macOS: System Prefs -> Displays -> Color; Windows: GPU control panel like NVIDIA Control Panel under 'Change resolution' -> Output color format), ensure the output is set to RGB, Full Range. IF THAT DIDN'T WORK The USB-C port might be negotiating a different color space like YCbCr 4:2:0. Force RGB output from your laptop's display settings or GPU control panel. Also, make sure HDR is turned OFF in both the monitor's OSD and your OS settings unless you're specifically viewing HDR content. HEADS UP The monitor has different picture mode settings per input. Your calibrated 'sRGB' or 'Custom' mode on HDMI doesn't automatically apply to the USB-C input. You have to set it up separately for that input source.

Question 2

there's a constant faint high-pitched whine or coil whine coming from the back of the monitor, even in sleep mode.

Accepted Answer

DIAGNOSIS That's power supply coil whine. It's an annoying but generally harmless manufacturing variance where components on the internal power board vibrate at high frequency. It's more noticeable in quiet rooms and with some specific brightness/refresh rate combinations. FIX You can try to 'mask' it by adjusting settings. Change the monitor brightness (sometimes 50% is worse, try 75% or 25%). If you're using a high refresh rate via overclock or specific modes, drop back to standard 60Hz. Ensuring the monitor is on a stable, non-vibrating surface can sometimes reduce resonant noise. IF THAT DIDN'T WORK If it's severe and the monitor is under warranty, contact LG. Some units have it worse than others, and a replacement might be quieter. There's no user-serviceable fix short of replacing the power board, which might have the same issue. HEADS UP The whine might change pitch or intensity when the screen displays very bright or very dark scenes. This is normal for this type of noise. It doesn't indicate an impending failure, just an auditory nuisance.

Question 3

the usb ports on the side don't work when connected to my pc with displayport, only with usb-c.

Accepted Answer

DIAGNOSIS That's by design, not a fault. The USB hub (the downstream ports on the side and back) only gets its data connection from the upstream USB-B port or the USB-C port. The DisplayPort and HDMI ports carry only video/audio, no data. FIX To use the side USB ports, you need to activate the hub. Connect the included USB-B to USB-A cable from the monitor's 'USB Upstream' port to a USB port on your computer. Now, the side ports will work, regardless of whether you use DP, HDMI, or USB-C for video. IF THAT DIDN'T WORK If you've connected the USB-B cable and they're still dead, check the OSD. Go to General -> USB-C Power or USB Hub setting. Sometimes it needs to be toggled or set to a specific mode to enable the downstream ports. HEADS UP The USB hub shares bandwidth. If you're transferring large files from a USB drive on the side port while also using webcam/mouse, you might see slowdowns. For high-speed devices, plug them directly into your PC.

Question 4

the built-in speakers make a horrible buzzing sound, it's not the source audio. is there a way to fix them?

Accepted Answer

DIAGNOSIS Yeah, this one's common. The monitor's internal 5W speakers are notoriously bad and prone to electrical interference, especially if you're using USB-C for both video and data. The buzz is often a ground loop or interference from the video signal. FIX The real fix is to not use them. Use your computer's audio out, external speakers, or headphones. If you must use them, try isolating the audio source. Use a standard HDMI or DisplayPort cable for video instead of USB-C, and see if the buzz disappears. You can also try plugging the monitor's power brick into a different outlet than your PC. IF THAT DIDN'T WORK Go into the monitor's OSD (Settings -> Sound) and ensure 'Auto Volume' and any sound enhancements are turned OFF. Sometimes these cheap DSP circuits introduce the noise. HEADS UP Cranking the volume above 60-70 on these speakers can cause the thin casing to vibrate and create a distorted rattling sound on top of the buzz. They're truly an afterthought; don't expect any quality.

Question 5

how do i clean the screen on this thing? the matte coating seems weird and i'm scared to ruin it.

Accepted Answer

DIAGNOSIS You're right to be cautious. The 27UK850-W has a semi-matte anti-glare coating that's more delicate than a standard glossy screen. Harsh chemicals or pressure can smear or damage it. FIX Use only a dry, soft microfiber cloth (like the kind for glasses) first. Gently wipe in one direction. For smudges, lightly dampen a part of the cloth with distilled water—just water, no additives. Wring it out completely so it's barely damp, wipe the screen gently, then immediately dry with another dry part of the microfiber cloth. IF THAT DIDN'T WORK For stubborn marks, a tiny drop of isopropyl alcohol (70% or higher) on the cloth, not the screen, can work. But this is a last resort, as repeated use can potentially degrade the coating over many years. HEADS UP Never use window cleaners, Windex, anything with ammonia or acetone. Never spray liquid directly onto the screen—it can seep into the edges and damage the electronics. The coating will show more 'sparkle' or grain under direct light when clean; that's normal for this type of panel.

Question 6

screen randomly flickers or goes black for a second, especially when browsing or with certain colors.

Accepted Answer

DIAGNOSIS That's the infamous 'IPS glow' or backlight fluctuation turning into an actual fault, often related to the monitor's Adaptive Sync or response time settings interacting poorly with the signal. FIX First, disable any variable refresh rate. In the OSD, go to Game Adjust -> FreeSync and turn it OFF. Also, in Picture Adjust -> Response Time, set it to 'Fast', not 'Faster'. Then, on your computer, ensure your output (from GPU settings) is set to 60Hz, not 59.94Hz, and that the color format is set to RGB/Full Range, not YCbCr. IF THAT DIDN'T WORK The issue could be a failing DP or HDMI cable incapable of handling the 4K bandwidth. Swap in a certified Premium High Speed HDMI cable or a VESA-certified DisplayPort 1.4 cable. The ones that come in the box aren't always the best. HEADS UP If the flickering is a rapid, localized shimmer, you might be seeing the physical anti-glare coating defect some units have. That's not fixable via settings and would require a panel replacement under warranty.

Question 7

i'm getting a 'no signal' message even though my mac is connected via usb-c, and the monitor is charging the laptop.

Accepted Answer

DIAGNOSIS The USB-C port is delivering power but not video data. This is a handshake issue, very common with this monitor's USB-C implementation, especially with macOS. FIX Power cycle everything in a specific order. Turn off the monitor, disconnect the USB-C cable from both ends, shut down your Mac. Now, turn on the monitor first, let it boot to its 'no signal' screen, then start your Mac, and finally reconnect the USB-C cable. This forces a fresh handshake. If that fails, try a different, high-quality USB-C cable certified for video. IF THAT DIDN'T WORK Go into the monitor's OSD menu (using the joystick control). Navigate to General -> USB-C Power and try toggling the setting. Sometimes switching it off and on again can reset the video data path. HEADS UP The USB-C port on this monitor only supports up to 60W PD, not the full 96W some MacBook Pros want. If your laptop is trying to draw more, it can destabilize the connection. Use the laptop's original charger if you need full power.

Question 8

my lg 27uk850-w won't turn on at all, no standby light, nothing. checked the outlet and cable already.

Accepted Answer

DIAGNOSIS You've got a dead monitor, no life signs. This is almost always the internal power board giving up, and it's a known weak point on this model. The external power brick is usually fine, it's the component inside that fries. FIX You're looking at a board replacement. Open the monitor case (plastic pry tools help), locate the small internal power supply board, note the model number, and search for a replacement online. It's a standard procedure: unplug the few connectors, unscrew the board, swap in the new one. No soldering needed, but you need to be comfortable opening electronics. IF THAT DIDN'T WORK If you're certain the power brick is outputting the correct 19V, then the main logic board might also be dead, but that's rarer. A full board set replacement is the next step, but at that point, weigh the cost against a new monitor. HEADS UP Be extremely gentle with the thin ribbon cables connecting the control buttons and the panel itself when you're inside. They're fragile and a pain to reseat properly.

LG 27UK850-W 27-inch 4K UHD Monitor

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