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Discussion Starter · #1 ·
This time I didn't do anything in the servicemenu! :)


My Hitachi CP-X275W has a stuck pixel right in the middle of the picture which appears after 10 minutes of use when the projector has warmed up. It's extremely annoying in dark movies when the blue dot suddenly appears in the middle of the picture. I have experimented with getting rid of it before by applying a small dot of some dull black tape on the screen where the pixel would be, but this created a black hole in black scenes (dark grey scenes :) ) and an even more noticeable black spot in bright scenes. I dismissed the idea then not bothering to try a yellow piece of tape that I thought would work.


Now, after having gotten rid of the vertical banding and the color uniformity problem in the service-menu, I realized that the only thing that was wrong with the picture was the stuck blue pixel. I decided to give the experiment with the yellow tape a go.


I didn't have any yellow tape lying around so I had to improvise. I found a plastic bag with a sticker which had some yellow in it. I peeled the sticker off carefully to preserve the glue on the back and cut a little square out and stuck it to the screen. I could still see some blue on the piece of tape when I stood right in front of it, but when I sat down in the sweetspot it was totally gone! WOW!!! This is too god to be true I thought so I switched to a completely white screen. WOW!!! :) There's no spot there! I expected a grey spot there now.


In my excitement I inserted movie after movie in the DVD-player and not even once could I see anything wrong where the stuck pixel was (is). The only time I see a spot there is if I walk close to the screen when a blue picture is projected. I guess the tape is stopping too much blue light from being reflected. But it's not visible from the seats. I'm VERY satisfied with myself now. :)


I tried taking a closeup picture of the spot with and without the tape but it was very blurry and didn't come out very well. It's difficult to hold the camera steady for a closeup shot without a tripod.





Why do I always discover these things at 01.00 AM?





Tor Arne
 

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Someone (don't recall who) makes a disk that is supposed to help with stuck pixels by alternately activating/deactivating them. Perhaps this could help with you "iffy" pixel.


I learned of this disk from the Dell site (long ago) when I had an LCD with a few stuck pixels but ended up swapping computers out.
 

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You can buy yellow electrical tape in automotive section of Walmart, but seems like yellow+blue=green dot. Gray screen can make dead pixel less noticeable.
 

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Discussion Starter · #5 ·
I did eventually manage to spot it in some very bright scenes because the piece of tape gets a dark edge when the projector is lighting is. It's like it casts a shadow. It took me a while to find it, though. :) It's also a challenge to find a tape that won't reflect the light too sharply back at me. Som tapes give a bright spot because of that.


I will see if I can find some thinner, dull tape today. :)



Tor Arne
 

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Discussion Starter · #7 ·
Yellow paint probably works fine. I can't paint my screen because it's a motorized roll-down screen and I dno't want to ruin it. I also want to be able to move the dot if I accideltally bump into the projector and the position of the dot moves. I keep my screen rolled down most of the time. I haven't tried rolling it up with the tape.


If you have a blue dot, use yellow tape/paint.

If you have a red dot, use cyan tape/paint.

If you have a green dot, use purple or magenta tape/paint.


I defocussed so that the dot became almost 2,5 pixels in diameter because a focused dot was so intense that it would show on the tape. The piece of tape is large enough to cover the 2,5 pixel area on the screen.



Tor Arne
 

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Quote:
Originally posted by Huey
but seems like yellow+blue=green dot.
If you were to aim a hypothetical yellow laser at that dot, it would look green, but that's not the case, adding colors doesn't work the same as subracting colors.


yellow + blue = green works when mixing light rays.


The thing is that the additive and absorbtive domains are inverses of each other. A "yellow" object absorbs blue incident light, so if taken from the primary colors, red, green and blue (added together in equal levels: white) would hit an object, the object absorbs the blue, red and green is reflected, red + green = yellow.
 

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I also have a stuck pixel in a VT540, however, my pixel is cyan in color. I'm wondering if that's not what the rest of you are seeing, as most LCD stuck pixels I've seen are this color. Theoreticly the complementary color for cyan would be red. Check this out:

http://www.geocities.com/SoHo/2365/color_wheel.html


Gary
 

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Discussion Starter · #12 ·
My pixel is definitely blue. If you have a cyan pixel then you have been very unfortunate and have both a green and a blue dead pixel in the same spot. If I look at a green screen my pixel will look cyan. :)



Tor Arne
 

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By far the majority of dead pixels are blue...not sure why this is....but I've been evaluating dead pixels for customers for years so I would say I'm a reliable source. After blue, would be green and then rarely red. On occasion, cyan, magenta, yellow, black, or white. Very rare though.
 

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Just talking out of my a**, but I'm guessing the reason most stuck pixels are blue is because the manufactures know that a stuck blue pixel isn't nearly as annoying as a stuck red pixel. They probably test the panels in the factory. If they don't have any bad pixels they get thrown in the red bin, only a few stuck pixels end up in the green bin, and everything else gets put in the blue bin. This keeps their yields up and complaints down.


-apnar
 

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Discussion Starter · #16 ·
I have found a piece of tape that works without giving a sparkle, but it block out a little too much blue, so a bright white pictures have a little yellow spot where the stuck pixel is. It's certainly not a problem as I only see it if I switch to a white test-screen and look for it. lol :)


I just took some before and after shots of the fix. The camera was in the exact same spot in both pictures. The pink and gren dots are faults of the camera and not the projector.

Before:
http://home.c2i.net/ahustvedt/images/pixelfix02.jpg
Here you se the blue pixel shining bright. The camera is zoomed in on the aproximate center of the screen to make it easier to spot the pixel. It really is a problem in dark scenes.

After:
http://home.c2i.net/ahustvedt/images/pixelfix01.jpg
As you can see the pixel is the same darkness as the surrounding pixels and therefore not visible on a black image. A black piece of tape would in this case give a spot which is darker than the surrounding pixels.


I'm still trying to get in contact with the dealer to get it fixed but they don't reply my E-mails or answer the phone. Next step is contact Hitachi directly. It's good to know, that it's possible to tweak it so that I can at least live with the flaw in case I don't get it fixed. At least it's only a single pixel. *Me looking on the bright side* :)



Tor Arne
 

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Discussion Starter · #17 ·
Ok. I now believe I have eliminated the blue pixel-problem by 99%. I have spent the last 30 minutes really staring at the area of the screen where the pixel used to be and I have not been able to detect it except for once where I saw it faintly. However, I can see it on the blue test-screen as a darker blue spot, and on the ****e test-screen if I really look for it. I watched Shrek and Jurassic Park III for the real tests because that will show if it's visible in actual movie-watching.


Shrek has lots of bright colors and I used it to see if the yellow tape would interfere with the colors. I didn't see any spot even once, except for in the DreamWorks sequence in the very beginning. The spot where the tape is made the blue color look very slightly darker than the surroundings. BUT! You have to remember I was really staring at area where I knew the pixel would be and I wouldn't notice it otherwise, it's really faint.


As for Jurassic Park III. The Universal-globe really made the blue dot obvious before. It's perfect now. :) Also, the flying-scene and the boat scenes were used to see if I could find the spot where the tape is. I couldn't see it even once. Green and red scenes are also perfect and not at all disturbed by the tape.


This is great news, the pixel is no longed a (big) problem. I do have to adjust the spot every time I watch a movie, though but I can live with that.


I tried with a yellow Post-It but it seemed to amplify the blue dot instead of dampen it. I don't know why. :) Instead I used some flat yellow paper-textured tape I got from work. I believe that I can make it disappear 100% in the white and blue test-screens by finding the right yellow color. But that's not going to be easy. I'm really happy with the results so far.



Tor Arne
 

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Necessity truly IS the mother of invention, good job.
 

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Quote:
Originally posted by tahustvedt
My pixel is definitely blue. If you have a cyan pixel then you have been very unfortunate and have both a green and a blue dead pixel in the same spot. If I look at a green screen my pixel will look cyan. :)

Tor Arne
A Cyan stuck pixel could also mean a Red pixel is stuck in the off state (giving blue + green = cyan). It would disappear on dark scenes but be visible on bright.

Wm
 
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