Well, today I decided it was time for some projector maintainence. Let's blow it out ( you would not believe how much dust 5,000 hours sucks in). I just cranked over 10,000 hours and now it's time for a retube. I'm doing the green and blue only as the red looks great. I decided to cheat a bit and mark the tube centers right out of the box with a felt tipped pen. It's just glass and must be cleaned off before you reinstall the lenses anyway. Then it came time to mark the center of the red (still mounted in the PJ), what a PIA. Than it occured to me, what are we really trying to do here? Are we really interested in getting the raster dead center on the tube face for the sake of the tube or are we simply hoping that by centering the raster on the tube that the center of the raster will fall exactly in the center of the focal plane of the lens? Measuring a tube face while it's installed can be a bit frustrating. Those who have actually pulled your lenses and tried to locate the exact center will understand what I'm saying. Assuming that what I really want is to have my static cross perfectly centered in the focal plane of the lens, I chose to make a perfect circle out of paper using the lens as a template. I checked to see if it fit tightly within the lens mounting on the projector. Then I folded it carefully in half (so you have a half circle) and then carefully in half again (so you end up with a quarter circle). Take a pair of scissors and just snip the inside corner and unfold. Now you end up with a perfect circle with a tiny hole in the center. Take the template back to the projector and place it on the tube face through the lense mounting and just touch the tube face through the hole in the template with a felt tip pen. This gives you a spot on the tube which is dead center on the lens focal plane, but may or may not be dead center on the tube face. I'm going to use these points to center my rasters. Back to work. I'll let you know how it turns out.
Chip S.
Chip S.
