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Discussion Starter · #1 ·
 http://www.users.bigpond.net.au/benn...phor_Usage.jpg


G'day,


The previous owner was using considerable less of the available phosphor area than my current setup shows, and I would welcome comments as to whether I should be aiming to use even more than the increase I have chosen. I have just completed the raster centering procedure ( I hope :) ) and the 3 guns seem to align/converge pretty good, but I do notice a slight softening of the focus at the corners. I suspect this is due to using more of the phosphor corner area and that the beam is undergoing greater deflection to get it to those points. I've done the usual search of the threads looking for a definative answer but a photo is easier to relate to.


Should I be happy with this or can I squeeze a little bit more out of it without compromising corner focus too much?


Cheers from downunder,


Russ
 

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It's just fine the way you have it. You're lucky there's no burn in form the old owner.


Note to all other NEC users: If you're not using this much phosphor area, you're not using enough..:)


Curt
 

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Discussion Starter · #3 ·
Thanks for the reassurance Curt :)


The clock on this unit registered 1050 tube hours when i bought it a few weeks back. The red and blue guns are 'micky' but the green shows some slight wear which surprised me for such a low hour unit. The contrast was set at 80 when i first saw it so that might explain things. I now run it at contrast of 60. I am umming and aahing about replacing the green tube but its generally not distracting when watching a widescreen presentation.


Cheers!


Russ
 

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Yes, the green NEC tubes wear first. Seems to be that way with almost every 7 or 8" projector over 800 lumens. I dunno why.
 

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Curt,


It's my understanding that the green tube wears first because almost 60% of the total image is generated by green.


Ken Whitcomb


Now Photo Research PR-650 equipped!
 

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Ken,


It seems that the brighter PJ's (as Curt mentioned) are the ones that spank the green tube first. For the lower lumen PJ's, the blue is the first to go. This seems to speak to the composition of the brighter image using the green to boost the contrast/brightness without showing a green push. How does that work?


Cheers!


Darrin
 

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Discussion Starter · #10 ·
kal,

when you run your image very close to the edge as you do, do you have problems converging correctly and maintaining good corner focus? It would seem to me that the greater the beam is deflected, the harder the electronics needs to work to keep it under control, which may ultimately lead to convergence drift happening sooner. I'm not doubting your wisdom at getting the use of as much as the phosphor area as possible, its just that when Curt/Doug give a 'thumbs up' to my current setup, my curiousity is aroused as to how your setup holds up over time.


Thanks for the comment on the picture I posted. It makes it much easier to explain things if you can see what you're discussing. I needed to adjust the image file from the camera slightly to portray the raster correctly, and hopefully this thread will help other newbies in the future.


Curt/Doug,

could my current usage perhaps be considered a "conservative" minimum usage, and that adventurous souls could use more, albeit with a greater likelihood of having alignment difficulties?


This is all new to me, and I am trying to understand all the different facets that make up a great picture. The subject of image coverage may be one of those subjects which has opposing camps of view :) It may also be that different brands and models benefit from different basic setup settings.


The distance from the centre of the green lens to the centre of the 80"x60" screen is currently 109". Factory setting is 118.75", which means I have moved closer by about 8.8%. This seems to tie in with other views of moving the projector closer to the screen.


Cheers!


Russ
 

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The first projector (1031Q) I got had a shot blue tube with some pretty bad wear on the blue. When I found the horizontal and vertical size pots I maximized them as much as possible and I then got blue white edges and yellowish whites, obviously because the blue tube was "well done" in the old raster area. My question is how come these projectors weren't setup initially to use maximum phosphor areas when the were "professionally installed" in board (bored) rooms, etc.? Setup convenience isn't a reason for using less phosphor area. In fact, anyone have any good reasons for using less phosphor area? I heard that some projectors have issues with maximizing the phosphor area - I guess it draws more power which could cause problems (I don't know what the hell I'm talking about). :D


Also, has anyone tried cooking their tubes out evenly if they have differing levels of wear? Now that I have nice blues I am noticing wear on my red and green. I guess it is just a cavet that one must deal with when getting into budget used CRT projectors. Hell, I'll take it over digital (no, make that disposable) projectors. Alright though, honestly, there will come a time when digital units will smoke CRT units, like maybe when we invent warp speed and that beaming stuff "that works on Star Trek." :D
 

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Quote:
Originally posted by benny
kal,

when you run your image very close to the edge as you do, do you have problems converging correctly and maintaining good corner focus? It would seem to me that the greater the beam is deflected, the harder the electronics needs to work to keep it under control, which may ultimately lead to convergence drift happening sooner. I'm not doubting your wisdom at getting the use of as much as the phosphor area as possible, its just that when Curt/Doug give a 'thumbs up' to my current setup, my curiousity is aroused as to how your setup holds up over time.
Russ,


No additional problems really with convergence by going closer, and I'm not sure of the focus difference (haven't done any A/B comparisons). Not really sure about convergence drift as I'd have to try both and leave them for some time to see. As it stands, nowadays I rarely have to touch up convergence anymore (seemed less stable when I first set it up). I do a quick static convergence as needed (which seems to be about once a month).


It may likely be a bit fuzzier in the corners but since I only use my projector for movies/tv, it doesn't really matter to me. Never did an A/B on this either I'm afraid.


Your image patterns seem very square and centered on the the tube faces - mine are trapezoid (larger at the bottom) and the red and blue are closer to the green edge then the outside edge so I leave 1/4" at the bottom right side of the red and 1/4" at the bottom left side of the blue. There's considerably more room on the edges as you move up the image.


(All relative to the picture you posted above of course - everything on the screen is reversed!).


Kal
 

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Discussion Starter · #13 ·
Thanks for the insight kal,

i think I fall into the adventurous soul category, so I may well move the projector closer and see what eventuates. The crosshatch patterns I show at the start of the thread were with the alignment/convergence controls pretty much zeroed. Now everything is converged on screen they look more like you have described.


Cheers!


Russ
 

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I suppose the one disadvantage with opening up the scans to use all the phospher is that lenses generally become less accurate toward the edges. Because of the requirement of having to bend the light at edges, grinding specs are way more critical.


This is why in photography if you stop the lens down by closing the aperture and hence only use the centre of the lens, the depth of field of the lens increases. (the depth of focus is better over significantly wider margin)


Unfortunately the exposure is longer cause it needs longer to gather enough light. (in projectors the light output drops significantly).


So I suppose if lower light output is acceptable and a less that optimum wear pattern is OK, and you need better edge focus or the ability to move the screen slightly and maintain focus, then I suppose a smaller image on the tubes would be OK.


But it does'nt look a good option to me !!!!


Graham
 
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