Have NEC LCD 40 inch tv which now has no sound or picture with coloured lines down he screen, is it fixable or has screen given up??

Replace the timing control board and it should work again.

If you wish to get some details; check the site linked here. Pull up older posts. Surf the site with patience. http://electronicshelponline.blogspot.com/
Line, faults & possible causes to LCD screen are given with illustrations. You can get an idea about the fault to an extent.

Sounds like a screen fault. The adhesive that attaches ribbon cables from the drive electronics to the screen has failed. Unfortnately this isn't fixable because the connection and spacing is too fine to get a 100% reliable connection. Some DIYers have used neoprene rubber tubing as wedges to hold the connections in place. That actually works. Search Youtube

If you wish to get some details; check the site linked here. Pull up older posts.Surf the site with patience.http://electronicshelponline.blogspot.com/
Line, faults & possible causes to LCD screen are given with illustrations.

If your LCD TV or monitor has stopped working, or is displaying one of the following symptoms, then it's a candidate for some new capacitors
- Flickering screen
- Screen image disappears after several seconds
- Dim screen
- Slow start
- Power LED on, but no picture
- Unusual colors and/or lines
The primary cause of LCD TV and monitor failure is caused by faulty capacitors. You can examine the capacitors in your LCD TV or monitor and actually see if they are bad.
If they appear bulged on top, then they need to be replaced.
New capacitors will solve a host of problems in LCD monitors and TV's and will extend the life of your monitor or TV by several years.
Check the cables, connectors and connections.
Take it to a repair shop.

It sounds that the LVDS cable; the cable that connects to T'Con board to LCD panel is loosely fitted. Check it first. If it is found OK, the panel itself should be suspected. If you wish to get more details, http://electronicshelponline.blogspot.com/ Pull up older posts there, either by its left side bar, or see it in Timslide option. Faulty screenshots of LCD TV screens, have been illustrated. Compare them to your TVs present screen view, and be sure. Check the site with patience.

You will first need to identify the LCD panel model # to your set. There should be a sticker on the back of the LCD panel assembly stating the panel model #.You will have to take the back cover off to expose the back of the LCD assembly. Do not make the mistake in ordering a replacement panel based off of your TV model # alone !!! Many TV manufacturers will use multiple panels in the same model series. Once you have your LCD panel model #, you can try Ebay or just google the LCD panel model #. If there are parts dealers with the panel, google should find them for you. Hope this helps

The tv could have a dead tv LCD screen panel because of it is damages by a person or an object by hitting it.Than the tv it is not worth it or repairable if it is require a new tv LCD screen panel.Will cost the same as a new tv,if tv require a new tv LCD screen panel replacement.The LCD screen panel tv that have multicolored lines run vertically on the LCD screen panel and people given it to u and said not thing.The tv probally have a dead tv LCD screen panel already,Sorry tv like this,it is a garbage tv now,it only can be used as a salvages tv only for it electronic circuitries boards only.

If you wish to get some details; visit the site linked here. Pull up older posts.
http://electronicshelponline.blogspot.com/
Line faults & possible causes to LCD & Plasma screen are given with illustrations. You can get an idea about the fault to an extent. Faults to all LCD & Plasma screen are similar, irrespective of its brand and screen size.

If your screen has a picture in the left corner with a small square with lines on it but still has sound...try this....

unplug your TV itself from the power source, then hold down the power button on the tv itself for 1 minute, then release.... Plug the tv back in and see if the issue is resolved. I just called LG customer support and a woman walked me through this process and it fixed the issue !!!! Hope this helps..