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Philips 37pf9986/12 Patchy Screen

Discussion in 'Philips TVs Forum' started by wuf810, Feb 11, 2005.

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  1. wuf810

    wuf810
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    Hi guys,

    Just bought Philips 37pf9986. I noticed from day one that when the image being displayed goes totally black (like the split second image between a program and adverts), I see patchy whitish areas on the screen. They are most obvious around the edges but do appear in the midle also.

    They are not very bright but enough for me to notice.

    Have any of you fellow owners seen this? Should I be worried?

    You can test yourself by turning contrast and brightness all the way down and see what you see. Obviously more noticable in darkness too.

    Let me your opinions. Thanks! Michael.
     
  2. jimsan

    jimsan
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    Have you got the TV properly fettled? It is possible to cause this effect by having the Contrast and Brightness settings wrong.

    Get back to us for the hot setup!

    Jimmy
     
  3. ianh64

    ianh64
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    Jimmy, your a used car sales man right?
     
  4. Alan D

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    wuf810 - if you have the brightness and contrast cranked up you are probably seeing minor variations in the backlight, which will all but disappear when you calibrate your set. Jimsan has posted this info several times (and I have posted almost identical settings) - but for quick reference:
    For Scart sources:
    Select Personal and adjust thus:
    Contrast:63
    Brightness: 50-55
    Sharpness: 3 (or 2) on preference

    If viewing via DVI, reduce the brightness to around 35
    Those will get you on track - the other options are mostly personal preference.
     
  5. wuf810

    wuf810
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    Hi guys. Thanks for the replies.

    Not sure this is the problem because my settings were not that far off from those you suggest.

    Also, if I turn the contrast/brightness down to 0, then I still see the patchy areas.

    Anyway, just to be sure, I've set my settings to the suggested values and will let you know what happens.

    In the meantime if you have any other suggestions, they would be gratefully received - don't want to send it back unless it really does have a problem!

    Thanks, Michael.
     
  6. jimsan

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    Nope, Ian, but I can see why you might think that....all this fettling and tuning.... I am, however involved in the Motorsport industry but in the design side....?
     
  7. MokerJoker

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    This 'patchy black' is something I also noticed when doing a plasma vs LCD comparison. My Iiyama TFT I'm looking at right now has similar problems; I've had it replaced two times and all three screens had problems with it. Changing brightness and contrast does not help, unfortunately. But for computer use I can live with it; I don't watch movies on my PC, however it can be distracting when playing games (Splinter Cell for example).

    It is one of my main concerns about LCD and the main reason I haven't bought a LCD screen yet. My other concern is faulty pixels, but that can be 'fixed' by buying from a reseller with a good returns/replacement policy. Patchy-black seems to be a more 'structural' problem of LCD's, based on my experience with the Iiyama and some posts on these forums.

    I'd be very interested to hear if you got the screen replaced and if that fixed the problem (or at least reduced it to acceptable levels). Or if you got similar results by tweaking the settings.

    - Jerry
     
  8. MokerJoker

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    I've just cleaned my TFT screen and noticed the patches have changed. I can actually 'push' the patches around the screen! In fact, I've managed to reduce the worst patches by spreading them out over a larger area. I don't know what's going on; it's probably the 'Liquid' in 'LCD' :). A warning though: It doesn't take much to damage the screen by pushing or rubbing on it. So be very, very careful if you try this. I've already seen too many screens with fingerprints 'burnt in', where the crystals are crushed or something.

    - Jerry
     
  9. wuf810

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    Hi all,

    Thanks for the replies. I guess the question is whether the "patchy" effect is inherent in all screens and whether I should learn to live with it or whether I should contact the supplier and ask for it to be replaced.

    My main concern is whether I am am being over sensitive - never spent so much money on a tv before and I guess I want it to be perfect. So anyone else thinking of buying this TV, bare this in mind. It really is a fantastic piece of kit and whatever the outcome I have no regrets.

    Michael.
     
  10. Alan D

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    Slight variations in the "backlight" seem to be common to most LCD screens - and of course "black" on an LCD isn't black, as there always has to be some illumination of the panel to produce a picture. With careful adjustment, as has been discussed, it can be reduced, but I have found that apart from very dark or black scene changes in films, it doesn't give me too much grief when viewing. If you had it replaced, there is no guarantee that it would be any better. As the technology improves this kind of "irritation" will no doubt reduce, but for now enjoy the plus points of the TV (and there are many of those!).
     
  11. LcdGuru

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    You'd be amazed at how bright the backlight looks without the LCD in front of it. The transmission of each component is as follows:

    Polarizers = 45%
    LCD Cell on white = 70%
    RGB Colour Filters = 33%
    So overall transmission on video white = 45% x 70% x 33% = 10%

    So video white is only 10% of the backlight brightness. So the backlight has to be dam bright to give you 500nits video white. And that thing has to be on all the time - even when you're displaying black. That's why blacks aren't completely black.

    Any slight variations in the LC cell gap, flatness of the glass or any of the optical components will cause uniformity variations. My Sharp 37" has some slight variations - however these are certainly within acceptable limits.
     
  12. wuf810

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    Hi guys.

    Well last night I did an experiment (well I thought I would wipe the screen) and tried what JVwaad mentioned and I have evened out the patches. Why does this work? What exactly is being moved?

    The other thing I noticed was that the LCD itself seems to rock very slightly in the frame. At first I thought this was strange but thinking about it, it makes sense that it is sort of floating - you wouldn't want it clamped down or would you.

    Anyway I am enjoying the TV. It really is fantastic. I have spoken to my supplier and because it needs a firmware upgrade, it will be sent back to Philips and checked out at the same time.

    Will let you know what happens. Thanks, Michael.
     

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