I was given a 1996 55" Magnavox rear Projection Model 6P5440-W103. TV. It Works good except for a slight green haze around anything that is white. I took the front screen off and noticed that the blue color gun has a crystal like substance or dirt under the lens. The red and green gun lens look clear except for the blue gun. Does any one have an idea as to what this can be. Can it be cleaned? Or do I need to replace it, and if so where do I look for new gun?