Hi I have a hitachi 50 inch projection tv and

If you are saying that the picture is getting darker and you have already tried to adjust the picture through the menu feature on your TV then it is more than likely the cooling fluid around the CRT tubes. Over time the fluid in these tubes gets cloudy and causes your TVs picture to become dull and distorts the color. You can google tv repair kits .com and I believe they will have a kit for your model.

This T.V. more than likely has a bad lamp. I don't know the model number so look up on ebay for a lamp replacement by model number after you inspect it and find it to look cloudy or exploded.

Ur convergence is problem.U know how to solders?Tries these website for convergence kit.Tv repair World.com,Tv repair kits.

Your blue picture tube is brighter than the other tubes. Try to do a convergence on it. If that doesn't do it, it sounds like you blue picutre tube is getting ready to blow. It is the same principle like a light bulbs. You know how they get bright and in a next few days they blow. That stands true to a picture set.

Backlight main video board is going,video board must change,about $500 with labors.

Have you cked 24volt neg and pos if not ok possible convergence ic and if you do change them make sure you ck the resistor by the ic's

They are nice TVs and if its free I would get it. You can get a Picture tube for it at the following link for 135.00 with free shipping and they provide instructions on how to replace the tube so a TV for 135.00 and 35 minutes work is a pretty good deal. Go to this link and leave an email with your model number and what you need and they will respond quickly to make sure you get the proper tube you need.
http://servicemanuals.vstore.ca/

http://home.earthlink.net/~oleg.filippov/ConvergenceFix.htm
http://cmpalmer.blogspot.com/2006/11/fixing-my-own-tv-part-ii.html
http://www.techlore.com/blog/entry/19694/Sony-Convergence-Repair-My-Sony-TV-has-a-distorted-picture-/

more info at ctechnicians.com email

Hmmm, could be anything from dirty optics, to a convergence problem....accordianman