Convergence (I think)

I have been on the internet trying to find the solution to this problem. I have a Samsung 42 in rear projection and my red color is completly out. I looked in thru a small crack thru the rear of the TV and can see that the blue and green colors are on and the red in the right side is either flashing or goes completly out. When its out the whole screen is green (in the front). I have been to the samsung parts online but need to know which part to purchase before making my decision. Does anyone have a clue which part needs to be replaced, I'm not a TV Tech but know enough to at least turn the TV off to work on it, which is a start.