What caused video failure?

backlight may have gone if your tv has one

Here are some basic treatment for a dark display.

1. On LCD TV, Some time missing or lose LCD strip from PCB connector. Solution- Clean strip and connector.
2. Some time missing LAMP, burning lamp is a major cause for dark display in LCD TV. If lamp problem with any display, Display show in sun lights. Solution- Check Lamp connection/connector. Clean connector or change Lamp.
3. In CRT TV, Fly back is faulted. There are no high voltages. Solution- Change or check fly back, Check out put transistor.
4. Some OLED Tv Use OLED lights for display shining and brightness. IF LED's or lamps are faulted there is no display in sun shine.
5. Before starting Troubleshoot display problem you need to conform and trace faulted stage of TV.
6. Don't Apply any miss use trick at home. Contact the professional repairing lab.
7. If you are full fault to understand your TV problem. Tip more condition of your problem.

try the flashlight screen test with TV on to be sure an image is showing, hold flashlight above at an angle, if you see a faint image the motherboard needs replacing

If the laptop comes on normally otherwise and is booting to Windows (you hear the normal startup sounds), look closely at the display and see if you can make out a faint image. It often helps to shine a flashlight on the display.

If the display is faint but present, you probably have a bad inverter board in the display. The inverter provides power for the display's backlight, and without the light the display still works but you can't see it. Inverter boards are available for most brands, they're not usually very expensive, and changing one isn't too difficult. A Web search for your brand and model and "replacement inverter" should turn up several sources. There are also YouTube videos showing how to replace the inverter in many kinds of laptops.

It's also possible the backlight itself is bad. If so, replacing the display is usually preferable to trying to replace the light. The light is built into the display and it's very difficult to replace without damaging the part or the display in the process. The display can be expensive, though.

If you're not sure that the computer is working, try starting it with an external monitor connected. If there's no display then, there's something wrong with the system board that's preventing the machine from starting up. Get that fixed, and it will probably fix the display trouble as well.

It's either the backlight lamp or backlight inverter is busted due to a power failure or fluctuation. Here's how to determine which is which:

1. Grab a flashlight.
   
2. Turn on the TV.
3. Shine the flashlight onto the screen.
4. If you cannot see any display even a faint one, the backlight inverter is dead, else the backlight lamps are busted.
5. Replace which ever is the culprit.

It's either the backlight lamp or backlight inverter is busted due to a power failure or fluctuation. Here's how to determine which is which:

1. Grab a flashlight.
   
2. Turn on the TV.
3. Shine the flashlight onto the screen.
4. If you cannot see any display even a faint one, the backlight inverter is dead, else the backlight lamps are busted.
5. Replace which ever is the culprit.

It's either the backlight lamp or backlight light inverter is busted due to the power failure.Here's how to determine which is which:

1. Grab a flashlight.
   
2. Turn on the TV.
3. Shine the flashlight onto the screen.
4. If you cannot see any display even a faint one, the backlight inverter is dead, else the backlight lamps are busted.
5. Replace which ever is the culprit.
   

When you tune to a station and get sound I presume the screen is black so do the following.
Place a bright flashlight against the screen. Look for an image around the edge of the flashlight.
If you see an image the problem is probably one of three causes.

1) Power to the inverter board is bad.
2) Inverter board has failed.
3) The CCFT(cold cathode fluorescent light) are dead.

Someone knowledgeable in electronics can diagnosis it.

If the computer seems to boot up just fine, but is not displaying a picture, take a flashlight and shine it at an angle on the screen, and see if you can see a very faint image of what should be displayed. If this is the case then the backlight bulb in your LCD panel has burned out. If you do not see anything on the screen at all even under a flashlight, then this could be indicative of a larger problem.

Hook the laptop up to an external monitor to make sure that you get a proper image on there first before you proceed. (Make sure that you try to change the laptop from internal video mode to external video mode if nothing shows up immediately. I have to press the Fn + F7 buttons on my T40p to tell it to use an external video monitor) If nothing shows up on the external monitor, then odds are that something else is wrong. Start by removing sticks of memory one at a time to see if they are causing the system to not boot up. (If memory is the problem, you should hear a series of beeps on startup though). Other complete video failure causes ussually have something to do with the Motherboard, orsome subsystem of it.

If you can see video on the external monitor, then either the LCD panel has gone bad, or the video cable has come unplugged. You can check this on most thinkpads by removing the keyboard and making sure that the video ribbon cable is securely in place.

If you can see the moving image faintly then it sounds like a problem with the backlight on the screen. Backlights can fail, but usually a cause is an impact of some kind.