hi folks, i have a sony hs1 with about 400 hours on the bulb.. if genuine hours.. bought the pj second hand about 2 years ago and i have used it very little since.. lately its started sort of pulsing while on.. what i mean by pulsing is that the picture will go slightly dim - then a couple of seconds later brighten up again... and then cycle like this going dim -then bright... its not a huge variation in brightness but you can notice it all the same. Its not a source issue because its still happening even with no source connected... Any idea on what this might be? The air filter? The bulb dying? Something else? Any ideas would be appreciated.. hope the explanation isn't too vague!