Pink Spot on Marquee 9500

Discussion in 'Projectors, Screens & Video Processors' started by Forrestcat, Jan 14, 2008.

  1. Forrestcat

    Forrestcat
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    Hello everyone

    Since having a fault with a neck board and having it fixed, there is now a small pink spot being projected onto the screen. This happens on all sources.

    Upon looking through each lens it appears to be on the green tube. It seems likely that the faulty neck board has damaged the tube or maybe some other circuitry. Any suggestions? Im sure its me being paranoid but it seems bigger today. Its less than 1 cm but enough to be annoying once you know its there. Could it get worse? When watching a film you do not notice it. Not sure whether to put up with it or start swapping neck boards around.

    thank for any advice

    James
     
  2. Barcoing Mad

    Barcoing Mad
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    Pink from a green tube. Can the phosphour become nuked in such a way it produces a different colour?

    Shove up a white field, then select each R/G/B colour in turn either physically covering lens or scrolling through colours on via remote. When is the spot apparent?
     
  3. Forrestcat

    Forrestcat
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    Hi

    Thanks for the speedy reply

    Tested on white screen without any source. Pink spot is definetaly on the green tube. When covered the spot goes away. You can see the spot on the tube face when looking through the lens.

    I have just tried with the projector off it does seem as though there is a piece of fluff on the lens. :) :suicide: I hope so.

    How easy is it to take the lens off whilst the projector is on the ceiling.

    thanks James
     
  4. Forrestcat

    Forrestcat
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    Hi

    Just getting a little excited :( Its not the fluff. I didnt think that could really cause the problem just hopeful.

    There is a little spot on the phospur you can just see it when the projector is off. Bugger

    Could this get worse? or do you think it happened when the neck board fried and thats it.

    thanks James
     
  5. barcoed

    barcoed
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    James,

    Sadly it sounds like spot burn to me. Is the spot exactly in the middle of the G tube?
    were you watching the projector when the neck board failed? Did you see a super bright spot in the centre of the screen briefly?
    Spot burn is often related to frame collapse when all the energy which is usually spread over the entire surface of the tube face is concentrated on a tiny (the size of the spot) area of the middle of the tube. This burns a spot on the phospher - for good I'm afraid. :(

    I used to have a Barco 701 which had a tiny spot burn on G - I used it for nearly four years and was only occasionally irritated when certain scenes would reveal it.
     
  6. Forrestcat

    Forrestcat
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    Hi Barcoed

    Thanks again. Yep must be spot burn. It is over to the far right luckily, I suppose I will just have to live with it. As long as it stays the same size!!! :D

    cheers James
     
  7. draganm

    draganm
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    that's a shame, and also really unsuall on a Marquee since it has the most comprehensive spot kill protection circuitry of any CRT. Whenever a scan failure is detected, the CPU should kill the cathode voltage emmediately. Unfortunately, even safety systems can sometimes fail. Luckilly for you it's not dead smack in screen center like it usually is.:(
     
  8. Forrestcat

    Forrestcat
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    Hi

    Yep very frustrating they only have a few hundered hours on as well. Oh well at least it all seems to be working well now.

    thanks James
     
  9. Forrestcat

    Forrestcat
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    Hi All

    Just an update. On a white screen alot more smaller pink spots are visbable, Do you think all of these were made at the same time. Should I still be worried even though the neck board has been fixed.

    thanks James
     
  10. Barcoing Mad

    Barcoing Mad
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    Just do a quick test and move the raster projecting a white (or green) field left/right, up/down to confirm that the spots don't move as well!!!!!
     
  11. Forrestcat

    Forrestcat
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    Hi Barcoing

    Its all a little odd. As thought the spot does not move. Indicating phosphur damage. However whilst having a good look at the white image you can see very light pink lines in the grain they look like tiny varicose veins. The lines are not straight and seem to cover most of the screen more so in the bottom left hand corner. Could this be dust? I do have a red carpet.

    Whilst having another good look into the lens there does seem to be a small piece of pink fluff on the inside of the lens. The larger pink spot however seems to be on the phosphur, can fluff get on there it does have the colour liquid over the tube so im not sure. what do you think?

    thanks James
     
  12. Swiss-Steve

    Swiss-Steve
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    Hey James,
    I would first pop the lens off, 4 hex bolts hold the lens on,
    can be done ceiling mounted no worries.
    clean the lens with a soft cloth like the one to clean your sunglesses.
    NO CHEMICALS

    Have a good look at the phosphor with the lens off, Take a picture if you can see phosphor damage. Post it up for us to check it out.


    I don't think that it is an issue with the spot kill citcuit, as this was checked when I fixed your board.

    I didn't check it before I fixed it, so possibly throught the heat damaged components, the spot kill circuit failed and has given you some spot burn, fingerscrossed this is not the case.


    One thing I normally see with a spot kill failure, is a vertical thin line rather than a blob.


    Maybe your glycol has some crystals and needs changing and cleaning of the bellows.



    Let us know how you go.


    Cheers
    Steve
     
  13. Mad Mr H

    Mad Mr H
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    I might have ONE new Marquee tube left in Green if you need it.

    Dust on the front of the lens will not be an issue, the focal point is at the screen not the lens face.

    It is possible that there is a break off part from the tube mounting that is flaoting in the glycol .

    Your is very good hands with Steve :thumbsup:.
     
  14. Forrestcat

    Forrestcat
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    Hi Steve and all

    Good to hear from you. I have taken the lens off, I have taken some pics but it is very hard to capture. I will try to explain what it is I can see.

    There are two like pin head in size dots on the green phosphur. This relates to the pink spots on the screen. Upon closer inspection it does look like they are floating in the glycol as you shine the torch it casts a shadow back onto the phosphur. On the projected screen there are more very faint pink peculiarities but these are not visable on the tube face.

    I think this is good news. Is this straight forward to sort out?

    thanks James
     
  15. Mad Mr H

    Mad Mr H
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    James,

    Looks like you have got yourself a floater or two! :rotfl:.



    (I know, Small things.................)
     
  16. Forrestcat

    Forrestcat
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    Hi Mad Mr H

    Yep its a bugger especially now that everyone keeps pointing out the PINK spot to me. Arrrrghhhh you hardly notice it! Honest......

    I think I just want reassurance that its ok to live with for now. Changing the fluid seems a big job taking the tube out and all.

    Cheers James

    I hate pink!
     
  17. Mad Mr H

    Mad Mr H
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    Think of it this way,

    At least its not a spot burn, that would be tears.
     
  18. Swiss-Steve

    Swiss-Steve
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    Hey James,
    I think that you need to clean the glycol,

    Bad news is that you have to drop the tube,
    Empty the glycol from the LC chamber,
    Filter it through a coffee filter or similar,
    then put the glycol back in.

    It may also be possible to just remove the tube, shake the tube, and the bits will make their way to the bottom of the LC chamber,
    But you risk the spots comming back through the glycol convection, lifting them to the top of the chamber and dropping again.



    Should take you about 30mins to remove the tube and drain the glycol,
    10mins or so to filter the glycol, (wear gloves, glycol is nasty to skin)
    be sure to leave a little air gap (air bubble) to allow for glycol expansion
    re-install tube and enjoy watching movies again.


    Also make sure the glycol is clear, not a yellowish tint, if yellow tint replace the glycol with new.

    Ask if you have any other questions, or not sure how to proceed.

    Cheers
    Steve
     
  19. Forrestcat

    Forrestcat
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    Hi Steve

    thanks again for the help I made need a little more :), see other post.

    Couple of questions, If I need to get some Glycol where is the best place to go? Do I have to take the projector down to remove the tube? It seems likely.

    Thanks James
     

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