Hi, I have a SAHARA AV-600 and an Optoma EZPro 610H, both are 3 years old. They both have very dim and fuzzy images, Lamps are new. Is this just an effect of the dichroics getting dirty or is it more serious deterioration? I have opened them up and the optics seem pretty clean. Would it be a simple job to undertake? What would it cost if I sent them away? Sorry if I seem vague or thick but these are school projectors and I have been thrown in at the deep end with maintaining them. Please help!