Black at bottom of screen then disapears when warmed up

perform the 'Flashlight test'
. LCD LED TV Repair No Image Blank Black Screen Flashlight Test How to Fix...

I think the electronics inside it have failed. My guess is that because its the picture only, it will fail in the same way if you play dvd into it for the same amount of time. The failure happens after it has warmed up, if you take it out into the cold you may get 1 minute more before it fails.
It needs replacing, its not cost effective to repair something like this, the failed parts may have partially damaged other parts in the unit so they could fail after a repair.

Got a heat related issue likely on main signal board---might be able to localize it (suspect a flat pack chip) with a hair dryer to heat the board just a bit.

I would suggest when turning set on cold---turn color all the way off and examine screen as set warms up---if red to some degree but gradually becomes black and white the issue is either a "touchy" red screen control on the screen/focus block or a problem on the circuit board plugged to the bottom of the red tube.

I guess the real question is how long until it is normal?

Can u get into ur tv menu with the universal remote?If u can't tries it with the tv manual buttons look at on the botton of ur tv have manual button said menu.Press it go into the tv menu.Look inside the tv menu for functions like Close Caption like CC1,2,3 and Text 1,2,3 make sure all CC1,2,3 and Text 1,2,3 turn it to all off.Black square box will disapear.Can't do it in the tv manual button etheir.Try website like Remote.com to buy the tv origial remote to close Close Captioning and Text 1,2,3 to all off.

Hi if your tv is lcd or dlp its an issue with the light engine.God bless you!

sounds like the closed caption is set to text mode . try turning off or setting the CC to off or CC1
hope this fixes it
Eric

I’m happy to help further over the phone at https://www.6ya.com/expert/eric_ab7c09ec01841771

sound like to me caption 1 is turn on .. try going into settings menu and shutting off close caption...

Im sorry to tell you this but it sounds like someone turned on the text feature on the closed caption? Go into the menu function, with the remote, and turn off the closed caption.