Samsung S90D OLED TV has picture but no sound

The checks in more detail

If sound returns, the problem is the external device or its connection. A Bluetooth headphone that remembers the TV may take over when it is switched on nearby. For a soundbar on HDMI eARC, the S90D has an eARC port that carries lossless audio. Check that the soundbar is on the right input, that the cable is good and that Anynet+ is on in Settings, General, External Device Manager. Set the Digital Output Audio Format to PCM or Auto; some soundbars cannot decode what the TV passes through, and a mismatch causes silence.

Restart both devices by unplugging them for a minute. For a single source, such as a streaming app or a cable box, check that source's own audio settings, such as a surround format your equipment cannot play, and try another app. Run Settings, Support, Device Care, and the Self Diagnosis Sound Test, which plays a melody to test the speakers. If the melody plays, the TV's speakers are fine and the issue is the source. If it does not play with TV Speaker selected, the speakers or the audio board may be faulty. Update the TV in Software Update and, as a last step, reset sound settings in Self Diagnosis.

If the sound is silent on every input and the Sound Test fails, contact Samsung with the model number. One feature is specific to this set. The S90D can pass sound to a compatible Samsung soundbar through Q-Symphony, and when that mode is on the TV speakers and the soundbar are meant to play together. If the picture works but a room is silent, open the sound output menu and confirm whether the TV is sending audio to the TV speakers, to the soundbar or to a Bluetooth device, because a pair of earbuds left connected nearby can quietly take the sound.