Exact model-family answer directory
Samsung S90C OLED TV troubleshooting
Samsung S90C OLED TV (QN55/65/77/83S90C*): what the S90C is; no One Connect box; an HDMI signal problem; input Signal Plus; software; the S90C beside the S95C, and a fix for each symptom below.
- What the S90C isSome sizes shipped with a QD-OLED panel and others with an LG WOLED panel depending on supply, but the behavior is the same: a dimming is the Auto Brightness Limiter.
Confirm the model first
Which units this covers, and how to tell yours is one of them
- Model numbers and patterns
- QN55/65/77/83S90C*
Published specification
What is true of this model and changes how you fix it
- Panel — QD-OLED2023 QD-OLED (self-emissive, perfect blacks, no backlight). Note some sizes shipped with a QD-OLED panel and others with an LG WOLED panel depending on supply, but Samsung's stated behavior is the same; either way it is self-emissive, so 'dimming' is the Auto Brightness Limiter, not a backlight.
- Smart platformInputs are on the TV (no One Connect box, unlike the S95C). Update at Settings › Support › Software Update.
- Gaming / HDMIFour HDMI 2.1 ports (48 Gbps) with 4K 144 Hz, VRR and ALLM. Turn on Game Mode; the Game Bar confirms the live refresh/VRR.
- No One Connect boxInputs are on the TV itself, unlike the S95C. Plug sources into the ports on the TV.
- An HDMI signal problemNo signal on an HDMI input comes from the source, the cable, the port setting or the TV's HDMI handling.
- Input Signal PlusInput Signal Plus enables the enhanced HDMI mode for a port. Without it a 4K HDR source can show no signal.
- SoftwareSettings, Support, Software Update installs fixes for HDMI bugs.
- The S90C beside the S95CThe two sets share a panel family, but the S90C has its connections built into the TV and is a little thicker. That makes it easier to install and to wall-mount without a hidden box, and it means a missing input is a port on the back, not a cable between a box and the screen.
- Protecting a QD-OLED panelKeep brightness at a sensible level for static content, use the screen-saver and automatic-off options, and do not leave a paused game on screen for hours. The TV runs a short compensation routine in standby, so a cycle that is cut off by unplugging the set defeats it.
- Using a soundbar with the S90CThe set supports Q-Symphony, in which the TV speakers work alongside a compatible Samsung soundbar. If dialogue sounds doubled or echoey, turn Q-Symphony off in the sound menu, and check that the TV's sound output is set to the HDMI eARC soundbar entry.
Where these figures were read. image-us.samsung.com/SamsungUS/samsungbusiness/tv-ci-resources/S90C-Spec_Sheet.pdf (Samsung US spec sheet) (QD-OLED, 4×HDMI 2.1 48Gbps, 144Hz, no One Connect)
Manufacturer support for this product line. Samsung Support — TV support. Official Samsung TV manuals, software, diagnostics and repair entry point.
Also read for this model. Samsung Support — Samsung TV support.
Exact questions
Questions that only have an answer for the Samsung S90C OLED TV
Is the Samsung S90C the same as the S95C?+
Both are 2023 QD-OLED, but the S95C adds the external One Connect box (all inputs off the TV) and is brighter, while the S90C keeps its inputs on the panel and is the value QD-OLED. Both run Tizen, lack Dolby Vision, and offer four HDMI 2.1 ports with 4K 144 Hz and VRR.
Is the Samsung S90C the same as the S95C?+
Both are QD-OLED, but the S95C has a One Connect box.
What is Input Signal Plus?+
The enhanced HDMI mode.
Does it do 144 Hz?+
Yes, on its HDMI 2.1 ports.
Where is the model number?+
On the back and in About This TV.