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Dust or Dead Pixel

Discussion in 'Projectors, Screens & Video Processors' started by azzo, May 9, 2002.

  1. azzo

    azzo
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    Can somebody please help me identify what a dead pixel actually looks like. I have noticed on my AE100 a green dot. Now it doesn't completely fill a pixel if you focus in to see all of the screen door effect. How is the matrix actually positioned. Is the Red panel behind the green panel, behind the blue panel or are the panels next to each other so a red, green and blue dot would be next to each other?

    Any help would be appreciated.
     
  2. azzo

    azzo
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    Ok, so I've done a search (I know I should have done this before), and Graham has exactly the same problem, but it looks like no one has responded to the question of whether a dead pixel should take up the space of a pixel?
     
  3. petrolhead

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    If it is a light dot then good change it's a dead pixle. I have one on my CS1 but it out of the way. If its dust you can focus in on it. Hope this helps
     
  4. azzo

    azzo
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    I don't quite understand that. How can a dead pixel be different to dust in terms of focusing? Am I being stupid?
     
  5. Der_Pobman

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    If its half a pixel and does not always show up then its dust. If you have a dead pixel it will be black. If you have a stuck pixel then the entire of that pixel will be showing either bright green/red/blue.

    What you describe is dust. I have one dust spec on my AE100. You cant see it on any of the test patterns. However you can see it on the shade of blue which is used as the background colour on my dvds menu system.

    However even then it is not very easy to see.

    If you have a stuck pixel you will see it all the time, and it will be very obvious.

    There was a photo of a screen with a stuck green pixel on this board about 1 month ago.

    I know for a fact some companies which are guaranteeing no dead pixels are getting returns from people who get some dust in their system.

    Petrolhead is right, if its dust you can also focus on it. You are basically focusing on the lcd panel which has the dust on, and focusing out the other panels.

    but I would say 99.99% certain that in your case it is dust.

    Regards

    Der Pobman
     
  6. azzo

    azzo
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    Thanks for the reassurance, I think I have two and you cannot see them on any test patterns. After cleaning the lens it looks like I've moved them slightly so they now appear as hollow specs around the pixel, so they must be dust on the LCD panel. Now does anybody know how to clean this. Idiots instructions and any idea if you invalidate your warranty would be great.

    Thanx Azzo.
     
  7. Der_Pobman

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    Azzo -- General Shanky did take his broken one apart, though he did not take any photos :( see his post:

    http://www.avforums.com/forums/showthread.php?s=&threadid=33617

    You never know he might be able to help.

    BTW if they have moved after cleaning the lense then how can they be on the LCD panel?

    Regards

    Der Pobman
     
  8. petrolhead

    petrolhead
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    Thanks also for that Der. I must have a stuck pixel then
     
  9. Graham

    Graham
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    Hi

    The first projector I had did have a very noticeable green dot - I believe it was a pixel rather than dust, because although it only took up part of the size of a pixel it was noticeable on a 6ft screen from 8ft back, and was pretty offputting on a dark background. Bizarrely, sometimes it was visible as soon as the AE100 was turned on, other times it could appear from 10-60 mins after turning on.

    Other pixels which looked like a vague green dot would get dark as a dark image appeared, but this one stayed bright green whatever the colour of the image. It was also clearly visible in the grey and black background screens when there was no input.

    Anyway, the problem was efficiently solved by the supplier and I got a new unit with no problems so far!

    Cheers
     
  10. azzo

    azzo
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    When I said they moved what I really meant was that they changed appearance. They are in the same place now, but almost hollow. It is not on the lens as this is spotless.
    I still can't decide, on dark scenes they are green. but on the pixel grid on service menu they are not. It is also worrying that graham had a problem with part of a pixel. Can this really be?
     
  11. Der_Pobman

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    Graham was it AV-sales?

    The unit I have got now was actually one which had been returned to AV-sales with a 'dead pixel'. For some reason AV-Sales did not bother checking it and send the guy a new one?!

    Anyway when my one broke they suggested i took one of these 'broken' ones. When we turned it on there was nothing wrong with it. No dead pixels at all. The only thing it has is one quarter green pixel, which is dust. Out of the 3 PJs AV-Sales had only one had a stuck pixel, it was blue, the other two were 100% perfect. I think they will be checking them from now on.

    If the pixel is stuck on then the whole pixel will be showing green/red/blue. If not then is just dust. Simple as that. Getting it replaced is just wasting peoples time. A stuck pixel will ALWAYS be visible with the possible exception of pure white images.

    Wait until you are at 1000+ hours, you will have plenty more of these green dots.

    The thing I dont understand is that they always seem to be green.

    If I look for the dust I can see it, and sometimes on a dark scene it will show up too. Can always see it in my DVD menus.

    If you dont like it then you will have to go down the sealed optics route. Just make sure you have a big enough cheque book!

    I wish panasonic had put all this in the manual, it would have saved them a LOT of bother.

    Regards

    Der Pobman
     
  12. azzo

    azzo
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    Agreed, it must be dust. Who knows why it is green. I will try to see it on the LCD tonight. Now how does the dust get there?
    Does it get sucked in by the fan and pass through the filter?
    How can we reduce the problem. Anyone one of any quiet air purifiers? - Thats if they work.
    Isn't dust mostly dead skin? If so then I'll ban everyone, myself included from entering the room!
     
  13. Der_Pobman

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    The dust just gets in :)

    Most likely through the air filter to be honest, I dont know if you have taken it out yet? Its pathetic to be honest.

    To reduce dust. Keep the room clean, dont smoke in there! Using a air cleaner will of course help, in fact I do have one (you should see how much dust it takes out). Clean the filter on the PJ ever 75-100 hours.

    The air filter I have is:
    http://www.argos.co.uk/webapp/comme...enbr=6970&type=big&thisMode=ols&cgrfnbr=69165

    Its very quiet on its low setting.

    Of course you could all wear bio-hazard suits and take in your own oxygen supply, but that might be taking things a little too far.

    Regards

    Der Pobman
     
  14. azzo

    azzo
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    Would these be the same sort of suits on Outbreak? But surely some of the fibres from the suit get in?
    I'll be checking out an air purifier and surge protector this weekend. This little baby needs all the help it can get.

    Azzo.
     
  15. Der_Pobman

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    I asure you the suits are fine. The guys wear them when washing down radioactive contaminated parts at the submarine yards in Severodvinsk and Nerpa (not that we ever have contaminated parts ;)). They have a some polymer based outer layer, so no fibres.

    However the helmet will muffle the sound, and you cant actually see that much out of the mask... so they are not ideal.

    Regards

    Der Pobman
     
  16. azzo

    azzo
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    Could you not use headphones. I hear dolby headphone surround technology is improving all the time. Alternatively you could somehow integrate mini speakers into the helmet. Wireless of course. How come you know so much about these suits anyway? I guess I'lll just stick to vacuming once a week to reduce dust.

    Azzo.
     
  17. Panicsony

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    Dust is not ususally on the LCD panel and can be anywhere in the optical path from the front of the lens through the complete optical path. For example the PT AE100 has 6 optical elements and a combining prism between the lamp and the lens, not including the three LCD panels. So there are 20 surfaces that could harbour dust. That is why it is vital to clean the dust filter regularly.

    As mentioned earlier in the thread. Dust is ususally not on the LCDs and hence can only be seen clearly IF the projected image is out of focus. If the "blemish" is there and clear when the image is in focus then it is on or clinging to the LCD.

    There are two types of dead pixels. DEAD or permanantly OFF, and LIT or permanantly ON. The LIT ones are more objectionable.

    Every panel/projector has a pixel policy and no manufacturer has a policy that includes zero faulty pixels. If anyone tried, no one would be able to afford to buy projectors.

    Incidently as green makes up 59% of the light output of a TV picture, green lit pixels seem more prevalent but are no more likely to be faulty than red or blue.
     

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