Any hardcore A/V geeks out there wanna try their hand at this?
First, go watch this. (Give it a minute or two to load.) I couldn't figure out how to describe the problem well, so I pointed my camcorder at my screen and recorded it happening. That video contains two short clips from the beginning of Star Wars - note the weird downwards frame offset and bands at the top of the frame whenever there's a bright flash onscreen - followed by some footage of my Mac displaying alternating black/white frames full-screen and watching the projector freak out.
The projector is a Seleco SIM2 HT200DM that was installed three and a half years ago. The problem's been happening ever since day one. There are two inputs to the projector, both long cables running through the wall (custom-made by the installer) to connect to the A/V equipment on the other side of the room: an S-Video connection to my receiver through which my TiVo and VCR are connected, and component connections to my PlayStation 2 which I use as my DVD player. No matter which input I use, I get this unstableness whenever there's a sudden very bright frame in the video.
I tried connecting my Mac directly to the projector via a short (6-foot) S-Video cable, and that did away with the unstableness; the same test video was rock-solid, which would seem to indicate there's something wrong with the cable in the wall. But what could be wrong? Is there a limit to how long an S-Video cable can be? Would a signal amplifier help? If I run a new cable, will I have the same problem?
Then I tried connecting my PS2 directly to the projector via the Sony component video cable, and I played the Star Wars DVD. The picture was still unstable whenever there was a bright flash! Why would this be happening? Maybe a dedicated DVD player wouldn't exhibit the problem, or maybe it still would?
I sent this projector in for repairs earlier this year (when the power supply died) and I mentioned this specific problem. The company told me there's nothing wrong with the unit that could cause this problem.
I guess what I need to know most is, what are those white bands at the top of the unstable image, which appear only for a frame or two? Is that part of the NTSC header? What could confuse a projector into showing part of the NTSC header? I'm at a loss to figure out what exactly is wrong and how to avoid it.