Samsung CU8000 Crystal UHD TV has sound but no picture

The checks in more detail

Shine a flashlight at the screen in a dim room: a very faint picture means the backlight has failed, and the TV needs service. If there is no light and no sound, check the power cord, the wall outlet and any surge strip, plug the TV into a wall socket, and unplug it for a minute. Hold the TV's power button for fifteen seconds to drain residual charge.

If the home screen appears, press Source and cycle through the inputs, looking for the one with your device. Check its HDMI cable, try another port and another cable, and test with the device's resolution lowered, since a signal the TV cannot show gives a black screen. A game console or PC set to a mode the CU8000 does not support, such as a high refresh rate on a TV that supports sixty hertz, will produce a blank picture.

Turn the device off and on, and the TV with it. Samsung's Smart Hub may show a message that helps, such as no signal or an unsupported mode. If the screen is black but you hear sound, check that the TV is not in a mode that turns off the screen, such as Picture Off in the Sound settings or Energy Saving's screen-off setting; press a button to wake.

A factory reset, found in Settings, Support, Self Diagnosis, Reset, restores the picture settings. Update the TV when it works. If a faint picture shows by flashlight or the TV is dead after a power reset, contact Samsung with the model and serial number from the back; do not open the TV, since the boards hold high voltage. Samsung TVs show an error code or a message on the screen in some cases of a failing panel,

and the Self Diagnosis menu has a Picture Test that displays a test pattern from the TV's own memory, independent of any source. If the test pattern appears clean, the panel and the board are working and the fault lies in the source, the cable or the input; if the pattern is flawed or does not appear, the TV needs service. You can open it through Settings, Support, Self Diagnosis, Start Picture Test, if you can reach the menu at all.

The CU8000 is a Crystal UHD set with an edge-lit LED panel, which matters for diagnosis: with the lights on in a dark room, a faint glow or a very dim image with the sound still playing means the panel is lit but the picture is not being drawn, whereas a completely black screen with no glow suggests the backlight or the power board. Shine a flashlight at the screen at an angle;

a ghost of the menu or the home screen points to a backlight fault. Try the TV's own Smart Hub button on the remote and see whether the menu draws, since that comes from the TV and not from the box. A source that sends a resolution the TV rejects, for example a game console set to 4K at 120 Hz, gives a black screen that clears when you lower the output on the console.