I have an older (much older!) version Mitsubishi rear projector 50" TV (model VS-585R), which was bought sometime back around 1989. It has always performed nominally, although I have had to replace the sweep board once. Recently I notice that it has begun to periodically turn itself off - usually after it's been on for a few hours already. Most of the time I can turn it back on again with no problem (although I did notice once when I turned it back on it turned itself off again immediately, within 1 to 2 seconds). Any ideas what this could be? Would a faltering sweep board do this? (assuming it might be the same problem as before) Or is it some other electrical problem? This set does have an Off Timer but I always keep it off/non-operational. Any thoughts would be much appreciated!