Screen only showing single line of video in center.

Tcon board possibly

Fault at its main digital board. Short circuited component/s at it. Contact any service technician; or the authorized service center. If you wish to get some details; check the site linked here. Pull up older posts.
http://electronicshelponline.blogspot.com/

The line is there because the vertical deflection unit - the one that spreads that line across the entire screen to form the image - has failed. Replacing it is a job for a professional, or at least an experienced amateur, and the parts will be quite difficult to find for such an old tv . 

Its sounds like a Frame collapse, you should check the voltages to the frame chip if it is fine you should try to replace this chip.

See if you can center the picture in the setup menu. It sounds like it's just off center.

samsung lcd tv 40inch modle .LA 40c 53F1R negitve video and brightness high plz send id [email protected]

Sounds like you have something wrong with the LCD screen, and there isn't much you can do about it except buy another top/bottom piece from NINTENDO.

Front and center speakers connected correctly and test sound works fine. Center speaker icon does not show on front panel of receiver (except during test) and i get no sound.

I have a similar problem on my CRT computer monitor (AcerView 76c). It is an old screen and I think it is just at the end of its life, much like your TV. Having some background in physics, I would be pretty sure that the problem is with the cathode ray tube's vertical deflection system. The horizontal deflection electrodes are working while the vertical one is not. This results in a display of a single horizontal line (or in my case, a few superimposed) in the centre of the screen. Where both X and Y (horizontal and vertical) deflectors fail then the electron gun firing would result in a single bright spot in the dead-centre of the screen.

So really, we have no choice but to move on and buy a new set as repair is probably just as, if not more, expensive than replacement with a new device. Seeing as your post was in 2007, I hope you managed to solve the problem.

Best wishes,
SZ (Sydney, AUS)