I am new to this area (projection) and have a question about a problem with a pair of projectors at our church. The rear projection screens have slowly developed what I call a hot spot(brighter than rest of area) in the lower left corner of the screen when viewed from the front. It is most noticable when the screens are in black out mode. One is much worse than the other. They share a common data feed from an Ectron scaler. We have tried all the adjustments on the scaler and cannot solve the problem. After reviewing the manual I cannot find an adjustment that seem to address this type of problem. These units are 5 years old and have had numerous bulb replacements. Both bulbs are fairly new. Any suggestions as to where to look would be greatly appreciated.