the screen on my tcl 43s446 is super dim and dark even with the backlight setting maxed out, movies are way too shadowy.

Diagnosis

The dimness you are experiencing on the TCL 43S446 is typically caused by a conflict between the "Local Contrast" algorithm and the "Dynamic Contrast" settings, which are designed to deepen blacks but often over-compress the mid-tones in darker scenes. This results in "crushed blacks," where shadowy areas of a movie become completely black instead of showing detail. Because this model utilizes a direct-lit LED array, the software attempts to dim specific zones to simulate high contrast; however, when these settings are misconfigured or glitching, the overall luminance of the panel drops significantly regardless of the master backlight slider. To confirm if this is a software-driven dimming issue versus a hardware failure, switch the Picture Mode to "Vivid." If the screen suddenly becomes blindingly bright, the issue is rooted in the contrast processing settings. If the screen remains dim even in Vivid mode with the backlight at 100, you are likely dealing with a failing LED backlight strip or a voltage drop from the power supply board (PSU) to the LED driver. This is common in the S-Class series if the TV is kept in a non-ventilated enclosure, causing the LED driver to overheat and throttle power to the lamps.

How to Fix It

To resolve the dimming and restore detail to shadowy scenes, follow this exact sequence to bypass the aggressive contrast processing:

1. Press the Home button on your remote and navigate to the Settings (gear icon) menu.
2. Select Picture, then scroll down to Advanced Settings.
3. Enter the Brightness submenu. Ensure Backlight is set to 100. Set Brightness (which controls the black level) to exactly 50; going higher will wash out the image, and going lower will worsen the shadowy effect.
4. Navigate to the Contrast submenu. Locate Dynamic Contrast and set it to Off. This prevents the TV from automatically dimming the screen during dark scenes.
5. Find Local Contrast and set it to Off. This disables the zone-based dimming that often causes the "too dark" feeling in the S446 model.
6. Go back to the main Picture menu and change the Picture Mode to Standard or Bright. Avoid 'Movie' mode for this specific fix, as it naturally lowers the color temperature and luminance.
7. Check the Energy Saving settings in the System menu and ensure Eco Mode is turned Off, as this overrides your manual backlight settings.

If That Didn't Work

• Perform a Hard Power Cycle: Unplug the TV from the wall outlet and hold the physical power button on the bottom of the TV frame for 30 seconds. Leave it unplugged for 10 minutes. This clears the capacitors on the power board and resets the LED driver logic, which can sometimes "unlock" a stuck dimming state.
• Factory Reset the Image Processor: Navigate to Settings > System > About > Reset & Reset. Choose Factory Data Reset. This wipes any corrupted calibration profiles that may be forcing the backlight to a lower voltage than the UI indicates.
• Test the Flashlight Method: Turn the TV on and shine a high-intensity flashlight directly against the screen at a close angle. If you can see a faint image of the movie moving behind the darkness, your backlight LEDs have failed or the LED driver on the power board has blown a capacitor. This is a hardware failure requiring a replacement of the LED strips.
• Disable HDR Tone Mapping: If this only happens during 4K HDR content, go to Picture > Advanced Settings > HDR and change the HDR Tone Mapping to On or Bright. Some content is mastered for high-nit displays that the S446 cannot reach, making the image appear dim by comparison.

Heads Up

• Avoid running the Backlight at 100% indefinitely if you use the TV in a dark room; reducing it to 80% can significantly extend the lifespan of the LED strips and prevent premature burnout.
• Ensure there is at least 3 inches of clearance around the rear vents of the TV to prevent the power supply board from overheating, which is the primary cause of voltage drops to the backlight.
• Be cautious with "Vivid" mode for long periods; while it solves dimness, it often over-saturates colors and can cause eye strain during long movie sessions.
• If you notice a "blueish" tint appearing along with the dimness, this is a sign that the LED phosphors are degrading, and the backlight assembly will need professional replacement.