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Marquee 8500 - squaring the raster

281 Views 4 Replies 4 Participants Last post by  JustGreg
The raster on my red and blue tube is not sqaure with the green. In other words, it looks like the entire raster grid has been slightly rotated. I believe this means that the scan yoke is misaligned on the tube. Is 1.5" (at the corners) off by a lot? I can bring it in using convergence but may think about fixing the scan yoke issue if the distance is significant. In other words, can you get the image exactly sqaured by adjusting the scan yoke?
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Yes, but be damned careful. You'll need to very carefully loosen the yoke from the hot glue so that it rotates freely (while the PJ is unplugged, of course). Again, lots of juice running through those yokes so be careful that you don't touch the windings while it's on.
Is 1.5" significant or should I leave it alone?
How stable is your convergence? If your convergence isn't stable because you're using it to fix a rotation problem, then you need to fix the yoke. If it's still plenty stable, then it's still best to fix the yoke, but I could understand avoiding doing so due to fear of damaging the yoke, or just laziness.
Originally Posted by Greg_R
Is 1.5" significant or should I leave it alone?
It depends on how anal you are. :p Me personally??...it would drive me nuts. I think it will you too now...you'll always be looking at the corners instead of enjoying a movie or game.

As you stated you can adjust it out with electronics but most prefer not to place any unnecessary loads on their pj's. Most go for the spot on mechanical setup so as to use as little electronics as possbile.

tse (scott) has said before the Marquee's electronics are robust and can handle what some would consider extreme compensation.

If it's ceiling mounted you'll want to consider taking it down to do the work. Picking at the hot glue while working overhead can't be any fun at all. It can be done but...ugh.

Also, it doesn't take much of a slip with the x-acto knife to cut a winding. Me personally I would try grabbing onto the yoke with one hand and pull on the 12/14 gauge wires going to it and seeing if you can't get enough movement without attacking the hardened hot glue. Make sure its powered off during this!

Work it back and forth but be mindful of the solder joints on the wires.

I was able to get 2 of my tubes to move enough this way with minor glue removal but the third (blue) required some extensive glue pickin'. (and I wasn't 'a-grinnin either!) :rolleyes:

Once you get it to move some in both directions, (if at all) power it up, let it warm up to full temp, and using the wires, try to get the adjustment you need. Plop some hot glue in one spot away from any windings to hold it in place once it's where you want it.

If it's ceiling mounted getting hot glue in the right place may not be possible. Just don't substitute epoxy for glue tho. Better to let it be without glue and have to tweek it now and then than to use something other than hot glue.

If it IS ceiling mounted and you have to take it down, that would be a good time to do the anamorphic (vertical) squeeze and LVPS filament voltage mods/fixes; if they haven't been done yet.

Best of luck! My $.02 FWIW

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