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Great example of Screen Burn

Discussion in 'Plasma TVs' started by jpd2, Apr 15, 2004.

  1. jpd2

    jpd2
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    have read loads on hear about screen burn, seen a great example of it yesterday at Currys Cribbs Bristol. Samsung 40" LCD had terible burn from Nemo menu. All other plasma's had been running longer than this unit with no sign's of damage. So if you are thinking of this model be CAREFUL, it may just have been set up badly or it may just be rubbish.
     
  2. reckless

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    Excuse my ignorance but I thought LCD screens didn't have screen burn issues?
     
  3. Gordon @ Convergent AV

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    They don't.....could this be a first.....

    What makes you think it was screen burn?

    Gordon
     
  4. jpd2

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    I assumed it is screen burn as you could still see a strong silloette of the Nemo menu image with other images on the screen (not apparent when the screen was off). This was not just a short term issue, as I was told it had been like that for some time, and according to the guy instore was not worth the cost of the plastic the screen is housed in, let alone the 4k it was on sale for.
     
  5. Gordon @ Convergent AV

    Gordon @ Convergent AV
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  6. DPF

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    There is a discussion here that talks about screen burn or something similar on LCD. In a later post a FAE (?) (service techo?) for an LCD maker says it is called persistance and that it is not permanent, interesting read.

    If you are interested in this field it might be worth following the original posters (on avsforum) experience with this to find out what the outcome is.
     
  7. Gordon @ Convergent AV

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    Persistance is something that affects LCD's but I have only ever seen it in moving images. Not on a display after it's been turned off. Persistance in the phosphor is the thing that scares the crap out of most plasma owners but that's another story....

    G
     
  8. calscot

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    One way to tell if it was a plasma or lcd is the price. A 40" Samsung LCD will probably cost almost twice that of a Samsung plasma.

    Was it nearer 2 grand or 4?
     
  9. Messiah

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    He already said above it was £4k. Guess it may indeed be a LCD then. Maybe worth making them an offer of £500 :)
     
  10. jpd2

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    It was definitely LCD, new square shape model LW-40A1, not sure I would give them £500 for it, the auction would have to start lower (perhaps they could put it on ebay, and we could ask them silly questions, no doubt we would get similar answers to the ebay scammers !!!)

    Gordon, probably is persistance, as I said in my earlier post it was NOT apparent when the screen was off
     
  11. rscott4563

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    So is this Samsung LCD using a different tech/screen to the rest of the LCD's out there or is this evidence that LCD's in general do actually suffer screen burn in the same way plasma's do??

    If LCD's do in deed suffer from screen burn then how come everyone seems to have been under the impression that they don't, including me (though I don't really know why I didn't think they did, maybe I read it somewhere or something?)??

    Ryan :smashin:
     
  12. LV426

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    There isn't anything to 'burn' in an LCD.

    On a CRT, the screen is coated in three phosphors (in stripes etc). A high intensity beam of electrons is fired at the phosphor. It glows a given colour in response. ALL of the light from a CRT is produced by glowing phosphors. Under constant bombardment from the electron beam, the phosphor ages - loses its ability to glow.

    On a Plasma, there are thousands of tiny pockets of gas. Each pocket has a phosphor coating (of a given colour) at the back, in fact. When an electric current is applied to the gas, it becomes charged - i.e. becomes plasma. The energy given off by plasma gas hits the phosphor coating and causes it to glow. ALL of the light from a Plasma screen is produced by glowing phosphors. Under constant bombardment from the electrically charged gas, the phosphor ages - loses its ability to glow.

    An LCD consists of a matrix of liquid crystal cells. When an electric current is applied to a liquid crystal cell, the molecules of the material all align in a given direction. When no current is applied, they float around randomly. When random, they diffuse any light passing through. When aligned, they polarise the light.

    In front or behind (doesn't matter) of the matrix, there is a polarising filter, set at 90 degrees to the orientation of the crystals, when energised. When energised, therefore, the combination of the polarising effect of the LCD cell, and of the filter, obstructs the passage of light. When not energised, light passes through. The whole thing is illuminated by a backlight. NO light is produced by the screen itself. Liquid crystals do not age (i.e. their ability to polarise, or not, light, doesn't change).

    What can happen is that some or all of the cells retain a residual electric charge, which causes the cells not to return to their natural (random, scattered) state immediately. They carry on polarising (slightly) which leave a latent image behind.

    The important difference, though is that the latent image on an LCD is transient - it is caused by residual electric charge and this will ALWAYS leak away to earth in time. It is not permanent. Whereas the ageing effect of phosphors is permanent and can only be "cured" by ageing the rest of the screen to the same degree - which is what Plasma "washing" programmes do.
     
  13. MAW

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    Illuminating stuff! But are you telling me the 'residual image' suffered by Pioneer in particular, only goes away cos the rest of the plasma goes as grey as the menu of the dvd you left on there? I find it hard to believe, having (famously) thought I'd cooked a virtually new demo 503MXE at Visionary. (they might still have it on display) Well when I say me, I had a saturday off and they left AOTC running, till it stopped and went back to the menu on Sat eve, I found it 'fried' on Monday, yet it recovered! It was fine after a few weeks, really really. This appears to defy the laws of physics, which is not good.

    LCD sceenburn I agree is simply 'not possible' in the model we have of it's operation method. So we need an explanation. So could some west country members pop in to the branch in question and see it for a 2nd opinion? No offence intended JPD2, just a very fascinating subject.
     
  14. Messiah

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    I wouldn't mind a trip over to Cribbs Causeway, maybe on Sunday, so if I do I will have a look and let you all know. If I remember I will taje a digital camera and get a pic.
     
  15. njr

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  16. TheBoingoBandit

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    Is this the same Visionary in Hampstead that has 'The Hits' playing on their plasmas 24 hours a day?

    That always amuses me.



    As for the Samsung LCD. I was the first one to post on the forum about it. When it happens, it's a lot more noticable than plasma burn-in.

    Regardless of it being temporary, I wouldn't pay that amount for it it to have that major flaw.
     
  17. LV426

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    Yes, that's exactly it. In fact, where visible burn-in become first noticeable, the actual extent by which the 'aged' phosphors are dimmer than the less aged ones nearby is tiny. Our vision is capable of detecting very small differences. So, in fact, the extent to which you have to similarly age nearby phosphors, to conceal the effect, is actually quite small.
     

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