I have a noticeable discoloration on one edge of my image that appears to be getting slowly more noticeable with time. Anyone have any thoughts as to what the problem is? Lamp? mirrors/color wheel? I just cleaned it out and that did not fix the problem (though the fans get noticeably quieter). The projector is a PB7200 from BenQ. Pictures of the discoloration are attached. I see it with any video input, or none at all (ie on the blue background).

I don't have any experience with BenQ, but I have to assume that all DLPs have the same basic internal optics. Therefore, what you are seeing looks like the light tunnel is failing.

On Infocus projectors, the light tunnel is a very small 4 -sided mirrored tunnel about 1" long. These sides are glued together. Over time (and heat) the glue fails and one side starts to slide in, causing the effect you see. It probably can be repaired but will require that you dismantle the optical section that holds the color wheel. The light tunnel will be directly behind the wheel, which, by the way, is very fragile.

So exercise caution, you don't want to cause more problems. If you break the color wheel, you are screwed. I did a quick check and I don't see that those parts are available.

Thanks! After looking it up, this does seem like the likely problem. I just had it opened to clean it, but I guess its time again to open it up and dig around. Any advice for fixing light tunnels? Will the problem be obvious?

It will be obvious once you get down to that level of disassembly. The only advice I can offer is to be very careful with the color wheel. Be very sparing with the glue. And if the light tunnel design is the same as in the Infocus, the sides will not be flush, but offset as you can see here.

This is a timely thread. My Infocus 4805 just started to do this now as well. Maybe this is the upgrade excuse I've been waiting for!

Well, I took the projector apart. Several hours later, I think I have fixed the problem. It does seem you were right, Sheridan1952, it was the light tunnel. The light tunnel was really hard to get to, but I managed to get it out and re-glue it (the old stuff was cracked and just fell right out). After putting the whole thing back together (I have two extra screws...not a good sign), the problem has gone away. There is a slight darkening on the bottom of the screen now, probably due to imperfect alignment of the light tunnel or something (there are some alignment screws that are glued in so I can't turn them). I would much rather have a slight darkening at the bottom of the screen, as I almost always run this in 16:9 mode so that area doesn't get used anyways. I'm happy enough with the improvement that I don't think I'll take it apart again unless it gets worse. Thanks for your help.