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Screen removal affecting geometry?

Discussion in 'Displays' started by Casey T, Mar 21, 2003.

  1. Casey T

    Casey T Member

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    Hi all.

    This is my first post here, so any help is very appreciated [​IMG]

    I just took the protective screen off of my Toshiba 42HDX82 to see how it would look (I had already had it re stacked). First impressions: the picture seemed brighter and (maybe this is just my perception) the viewing angle seemed to improve a bit.

    However...

    The geometry of the set is way off. I have a very noticeable pincushion effect (bowing inwards). I assumed that some convergence would have to readjusted, but the harsh pincushion is a bit of a surprise. Is this also the result of the focus plane changing or could this be from screen sag? I sued the oft-documented magazine method, and my screen seemed pretty tight, but I'm not sure if a little difference here could be the culprit.

    Again, any input is appreciated. Thanks!

    Casey
     
  2. Jim Doolittle

    Jim Doolittle Member

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    Are you sure you put the fresnel lens back in to the set with the proper orientation?
     
  3. Casey T

    Casey T Member

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    Didn't tocuh the fresnel or lenticular screen, actually (the set was restacked for me at the shop). When I have the protective screen on, everything's perfect, geometry and convergence-wise (it's at the back of the stack). It's only when the protective screen is removed completel that there's a problem.

    Thanks.
     
  4. Jason Spencer

    Jason Spencer Well-Known Member

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    I also tried a restack with similar results. In my case I definatly had screen sag (it was very noticable) and the picture was crazy wavy. I just put the screen back in the front. I'm thinking of a restack instead. It just seemed too flimsy with just the lent/fres screens without the "mirror". How did you like the restack picture? Was the only benifit the elimation of the "mirror" effect? Or did the quality improve any?
     
  5. Casey T

    Casey T Member

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    I founf that the viewing angle was somewhat improved, and that the birghtness was definitely better.

    I at first thought I had sag - the lent and fresnel didn't seem perfectly sung. But when I relaced the mirror screen, i found that they still weren't perfectly snug, but all my picture problems disappeared.

    I've been told a 56 pt convergence may solve this.Anyo pinions on that?

    Thanks.
     
  6. Jason Spencer

    Jason Spencer Well-Known Member

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    Was the improvement when the screen was removed, or after the restack? I wanted to know how it looked with a restack. I'm either going to do a restack or just replace it with a non-reflective screen.

    In my case after removing the screen it was too wavy to use convergence to fix it, but I guess with an only slightly bent stack the convergence/geometry adjustment could "correct" it. I'd rather have a flat screen though, so to me any bowing is unacceptable, I don't want to just "cover up" the problem...
     
  7. Gregg Loewen

    Gregg Loewen Video Standards Instructor, THX Ltd.
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    Hi guys!

    This is the side effect of removing the glare screen from the stack. The bezel is quite flexible and will cause the screen to concave inwards when being tightened down.

    The above should not be a problem if you do geometry and then covergence. You will still notice the concave when viewing from the sides but not from the "major" viewing area.

    Regards

    Gregg
     
  8. Jan Strnad

    Jan Strnad Well-Known Member

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    I'd get an acrylic non-reflective screen from a plastics store. Have them cut it to size. You'll get a protective screen, which is a good thing, but cut down the glare dramatically, and no sag.

    Jan
     
  9. JohnnyG

    JohnnyG Well-Known Member

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    It just wasn't good enough for you the way it was, eh?! [​IMG]
     
  10. Casey T

    Casey T Member

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    Well, I find the distortion form the screen removal actually kind of annoying, so it looks like I'm going to place it back from where it came [​IMG]

    The main reason I had removed the screen was because of two wavy horizontal 'smudge" lines at the top and bottom of the screen. I checked the protective screen and it seemed clean, so i'm not quite sure what's causing this.

    If anyone has any information on what (if anything) can be done about this, I'd be most appreciative.

    Thanks!
     

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