I have a projector hooked up to a computer screen. The projection of the screen used to be very clear and easy to read, but now the projection is very faint and nearly impossible to read. The "change lamp" button does not light up when the projector is turned on. I tried adjusting the contrast on the computer as well as on the projector itself, but nothing seemed to help. Do I need to change the filter on the projector, or is there an electronic setting that needs to be changed?