I can't remember the TV tech's name, he posts here and I think he is from Texas.
He turned me on to these quick and easy tips for rear projection TV's.
Make sure that both sides of the "screen" (it's actually a lense) are clean, clean in accordance with the manufacturers instructions.
Open the TV up to access the "inside" of the box, this is where the bottom cover (cathode ray guns) project onto a mirror (top or there abouts inside of the box) which then project onto the inside lense.
Clean the inside of the box. Cobwebs, dust, dog/cat hair, whatever. Use a vaccume cleaner and compressed air. I was able to use windex on the mirror as on mine it's one solid piece of mirrored glass.
Make sure that the inside of the box is black and that it is sealed so no outside light sources can leak inside.
Your projection guns "SHOULD" have a protective cover on them.
Mine did.
I took the vacumme cleaner and a dust wand and removed the dust, then I used compressed air and blew the loose crap off and then finally I used windex to clean the gun covers.
Reassemble it and try it out.
I have a Magnavox 48 inch rear projection TV that's 13 years old, at about 7 years the picture was washed out and faded, at 9 it was blurry and very dim with white spots on the screen.
I had made 6 military moves with it across the USA with it, I figured it was time to buy a new one.
At 11 years the picture was finally crappy enough that I was going to drop some gun money on a new TV.
I posted here and I was given the above advice.
After I cleaned it the picture was sharp and bright, and it was very crisp.
The only problem was the white spots.
It was explained to me that the cooling fluid in the guns had probably grown mold inside of them and needed to be cleaned and have the fluid replaced.
This is a "DANGEROUS" evolution, so I spent the money on a professional and had him do it.
He spent almost three hours removing the green and blue guns, cleaning them and replacing the fluid.
It's a simple job to do as long as you understand the innards of a TV.
I don't.
I think it's the red gun tube that doesn't grow mold, so he didn't replace that fluid.
The crap that came out of the gun reservior was NASTY and smelled like ass!
My hint to you is that if you do have a "professional" come do your TV don't use his fluid.
The guy that did mine used a name brand coolant and was going to charge me $35 a bottle.
I did an internet search and found that I could mail order it for about $12 plus shipping.
Guess where he makes his money at.