Causes
- Wrong input source selected in the OSD — the EX2780Q has multiple inputs (DisplayPort, two HDMI, USB-C) and remembers the last one used. After swapping cables or connecting a new device, the monitor can be showing an input with nothing plugged into it, so the screen stays black with a "No Signal" / input notice.
- Loose, bent, or low-bandwidth cable at 1440p/144Hz — driving 2560x1440 at 144Hz needs a good DisplayPort 1.4 (preferred) or HDMI 2.0 link. A partially seated connector, a kinked or worn cable, or an adapter that can't carry the bandwidth makes the panel fall back to a blank screen or intermittent blackouts, especially during full-bandwidth desktop use.
- USB-C connection that the monitor cannot reliably drive — the EX2780Q's USB-C port does not deliver power, so it relies on the laptop's own supply. Some laptops won't reliably light the panel over USB-C (particularly ones without full DisplayPort Alt Mode on that port), leaving a black screen even though the monitor is on.
- The monitor sleeping and failing to wake — when the PC sleeps, the monitor enters standby with the LED on, and a failed wake sequence or a stale handshake can leave it hung on a black screen until you power-cycle it or send it back into sleep and wake it again.
- GPU driver crash or a resolution outside the panel's range — after a driver update or a game forcing an unsupported resolution/refresh, the EX2780Q can go blank until the output is reset or the resolution is lowered.
How to Fix
- Select the correct input source — press the joystick on the back or use the remote, open the OSD and go to the Input menu. Choose the input your cable is actually connected to (DisplayPort, HDMI 1, HDMI 2, or USB-C). You can also enable Auto Switch so the monitor follows the active signal automatically.
- Reseat and test the cable — power down, unplug the DisplayPort/HDMI connector from both the monitor and the PC, check for bent pins, and re-seat it fully so it clicks into its latch. Try a second port or swap the cable for the included DisplayPort or a known-good HDMI 2.0 cable to rule out a bandwidth or pin fault.
- Wake the panel from standby — press any key or move the mouse to wake the PC, then press the monitor's input button (or remote power) to wake the panel. If it stays black, press the monitor's power button to put it to sleep and wake it again — this resets the handshake without unplugging anything.
- Power-cycle the monitor for 30 seconds — unplug the EX2780Q from the wall for about 30 seconds, hold the power button to drain residual charge, then plug it back in. This clears a hung standby or handshake state and is the most common fix for a stubborn black screen.
- Test at a lower resolution and refresh rate — with the panel connected, set the PC to 1920x1080 @ 60Hz (or use a different device) to see if the image returns. If it does, the black screen was a bandwidth/cable issue at 1440p/144Hz; raise the settings back up only with a cable that can handle it.
- For USB-C, power the laptop and confirm DP Alt Mode — plug the laptop into its charger (the monitor's USB-C delivers no power) and confirm the port supports DisplayPort Alt Mode. If it doesn't, use the HDMI or DisplayPort input instead for a reliable picture.
- Reset the GPU output — press Win+Ctrl+Shift+B on Windows to restart the display driver without rebooting (or use Ctrl+Opt+Shift+Pwr on newer iMacs in similar situations). If a driver update started the problem, reinstall the latest stable graphics driver or roll back.
- Connect a second device to isolate the fault — plug in another PC, laptop, or console. If the EX2780Q still shows no signal on that device with a known-good cable, the panel/board is the problem and the monitor should go back under warranty; if it works, the fault is in the original PC's GPU port, cable, or driver.