Picture gets darker when light in room is turned off!

Hello Dear
please check coils which are very near to LVDS jack these are open these are interface coils between panel and main board some are open
Thanks
M Nasir

If your TV seems to be darker than you think it should be, it is possible that the problem is with the light sensor. The light sensor will automatically adjust the picture brightness based on the ambient light that is in the room, (i.e. if the room is bright the picture will also be bright, if it is dark the picture will also be dark).

To turn this feature off go to Settings > General Setup > Light Sensor.

Menu - Picture - Energy Saving

Various settings including Off.

Short Answer:
The distance calculation is the diagonal size of the screen times the throw ratio of the projector (x/12 for feet).
If the projector has a physical zoom this plays in as well, throw ratios are usually displayed at 1x or for the whole range (e.g. 82C; 1.2 zoom means 1.43-1.71 throw).

Details:
Light calculations are somewhat inside the scope of this question, but suffice it to say, they aren't fun to do IMHO which is why I like the online calcs for a quick reference. Rule of thumb, the brighter the room or bigger the picture, the brighter the need.

If you don't want to do the calculations yourself, there are hundreds of calculators out there. Projector Central has a good distance calculator that is preset for actual projector specs. I use it often so I don't have to mess with the calculations. Just go to their website and select "Calculator Pro" at the top. It even does estimated light readings (we aim for 80fL because of the bright room environment we have to deal with, but for controlled lighting 30-50 is a good range too.)
There are also apps available on Android and iOS like AV Tools or Alford Calc.

If you want to do precise calculations, you need to know the size of your screen, the throw ratio of the projector and the brightness of the projector (and the brightness of the room) and the reflectivity of the surface (gain).
The latter two of these deal with picture intensity, the fact as your image gets smaller, the image gets brighter; to a point that it can be uncomfortable to watch. The opposite is also true, that as the the image gets larger, it gets darker since the amount of light coming from the projector doesn't change.
And finally, the more ambient light in the room, the darker or more faded the image will appear as it competes with other light sources.

That depends on the ambient light and your own preferences. That's why there are different settings. Is the room dark or well-lit or something in between? Do you want the picture bright, or do you prefer it a little darker?

Go to settings and change the lens exposure time or just set a focus point for the picture on a darker spot to change the white balance

Sounds like you have bad inverter boards, these are what light up your picture.

projection bulb needs replacement...how new is this tv set?

Try hooking the TV to a different outlet fed by a different breaker. Does the problem go away? If so, the culprit may be a wiring problem in your house that is causing the TV not to get enough power unless the dining room light is on.If in doubt, consult an electrician to make sure both the dining room light and TV outlet circuits are working properly.

The tv has a room light sensor,
shine a bright light at it , does picture get brighter?
other wise when it is cool open the bulb door , is it coated or blackened, Don't touch bulb at all.

and a heavy covering of dust on internal mirrors will cause the same effect.
you will need help to clean it.