I recently bought a home with a nice home theater setup. It has a Sim2 300HT Plus projector with a 150" screen. One minor issue that I find annoying is a few black spots on the screen. The spots are visible only when the background of is a solid light color. These black spots originate in the projector, rather than the screen. I confirmed this by seeing the spots change location when zooming in/out. The projector documentation only mentions cleaning the outside of the lens, which I have done. The manual states that I should not have to clean the interior of the projector. However, it looks like the black spots are coming from the interior somewhere, as cleaning the outside doesn't help.
Skimming through the forums, I saw a few threads about changing the filters. Do you think that's what I need to do? If so, could someone direct me to a thread or website that describes in detail how to do this, as it is not mentioned in the projector documentation?