It sounds like you may be experiencing a color uniformity issue with your 50-inch QLED ONN TV. This is a common problem with LCD and LED TVs, where the color and brightness of the screen can vary slightly across different parts of the screen. The brownish tint you are describing is often caused by issues with the backlighting system or the quality of the panel.

There are a few things you can try to fix the issue:

Calibrate the TV’s settings: Adjust the color temperature, brightness, and contrast settings to see if you can reduce the brownish tint.

Check for any external factors: Make sure that the room is well-lit, and that there are no reflections or glare on the screen.

Check for firmware updates: If there is an update available, it might fix the color uniformity issue.

Try a different HDMI cable or port: Sometimes, the problem could be the cable or port you are using.

Contact the manufacturer: If none of the above steps work, you may want to contact the manufacturer or the seller of the TV to discuss a repair or replacement.

My tv had lines across the screen