Black rectangle appears on 36" CRT. Needs reset?

The closed caption function is ON with your TV now. Make it OFF.

The dark rectangle appears because you have the closed captions on and set to TEXT. Closed captions set to CC1 puts the words on the screen and TEXT puts a black box on the screen. Go into the menu, navigate to the page with closed captions and set your captions to OFF.

The rectangle is the set or the box if used in the closed caption area is set or TEXT is selected--turn that off.

Won't change channels: up or down? Direct enter a channel with the remote 03 and enter to see if it works that way.

Also need to know if you are using a box for signal.

Resolve the text issue first so you can clearly see the regular screen.

Let me know what happens and what you have tried.

I do know that on Zenith CRT televisions of the 1990's this will happen and all I did to fix it is to go to the menu and turn the text feature off. This may be true with your Sharp as well.

PIP is on (Picture in Picture) either from your cable box or the TV. Check your remotes for "PIP". If you still have an issue, post a comment and I can help you more

The box you're seeing is the "closed caption' box. You need to use the remote and disable CC mode on it, and the box will go away :)

captioning on turn off with remote.

Mike,
Go into menu settings, closed caption and turn off closed caption... What you're seeing is the text box of closed caption.
Bill

Perhaps the caption is on?

Try a "hard reset"===unplug AC for a long time, like overnight.Let me know if there is any change.