My Hitachi tv model # le55a6r9a has a black screen. What do I need to do to fix it? It does have a picture when I shine a light on it when the room is dark so I think its the backlights.

SOURCE: I have a phillips magnovox

The coolant fluid in the blue and green picture tubes is in need of changing.Unless you have done this before I do not recommend that you attempt this repair.A shop shoud be able to make this set look like new again for about $275

SOURCE: vizio p42 very dark screen backlight off

There is no back light in plasma TV, Base on the description, the Z Sustainer board is bad. Replace the board will fix the problem.

SOURCE: Sony cyber shot dsc-t10 backlight not working

Hello,

Yes, the backlight is a separate part. It can be removed from the LCD and replaced.
The following video shows how to replace the backlight in a Sony camera.

http://www.desmontalo.com/?p=275

SOURCE: How to fix fix my Hitachi Projection TV - model # 61WX01W, got darker and darker and now all dark. Has 3 pictures tubes. How do I fix the problem?

Likely what you have is the three tubes each have a filament--not unlike a light bulb-----someone would have to trace the filament voltage (usually comes from power supply) from source to the three tubes---filament connects to each tube with two connections and is usually 6.3 volts.

SOURCE: my Sony model KDL-40S4100 is dark. I have a picture and can see whats going on, but the screen is just not bright. I'm thinking that its the backlight, but how can I tell for sure??

The only way to tell if a backlight (if set has one) is bad is to measure the voltage on the power board and at the back light itself---most voltages are marked on power board or a Service Manual would pinpoint them.

If the voltages are normal and back light is on but DIM only option would be to replace the board that drives it or the actual back lights'

If you Google the model number with "parts" you should be able to locate the back the parts involved.