Samsung S90C OLED TV shows no signal on HDMI

The checks in more detail

No signal can come from the device, the cable, the port, a setting or a handshake failure between them. Start with the basics. Check that the device is on, not asleep and set to output video, and that you chose the right input with the Source button. Unplug the HDMI cable at both ends and plug it in firmly, then try another HDMI port on the TV and another cable, since a worn or low-grade cable is a very common cause, especially for 4K HDR.

Turn the device and the TV off, unplug them for a minute and power on the TV first, then the device, which restarts the handshake. Then the settings. Open Settings, General, External Device Manager, Input Signal Plus, and enable it for that HDMI port, since 4K HDR and high-refresh signals need the enhanced mode, and without it a source can show no signal. Turn on HDMI-CEC, called Anynet+, if you want devices to wake together, or turn it off if it causes the TV to switch inputs unexpectedly.

Check the device's output: set a console or a box to 4K at 60 hertz first, then raise the refresh rate; a source set to a mode that the cable or the port cannot carry gives a black screen, and the device's menu can reset to a safe resolution. Try Game Mode on and off. Update the TV software and the device's firmware. Test the device on another TV, and another device on this port, to find which side is at fault. If no device works on any port with good cables, the TV's HDMI board may have failed, and Samsung service with the model number can advise.