Panasonic 'dirty screens'

Discussion in 'General TV Discussions Forum' started by BillyNomez, Dec 15, 2002.

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  1. BillyNomez

    BillyNomez
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    Have seen this thread crop up occasionally, recently mentioned for a TL32pl10 or similar, I have a TX32ph40, but not seen satisfactory answer yet.

    - what is the cause of very faint but noticeable patches on a screen that are not part of the moving picture and seem to show up in my case with a single strong light background colour, like the screen needs a dust but its on the inside :confused:

    Not always aware of it, but its there.
    Anomaly of digital processing ? The panny pic enhancements dont seem to do much to help.

    Ideas ?? BR
     
  2. staffspeted

    staffspeted
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    Got the same problem on my new Toshiba 32ZD26P , I asked the group about and got the impression that it seems to fade with time but what it is exactly wasnt made clear!
     
  3. keyser

    keyser
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    I noticed a bad dirty screen effect on my 36zd26p, and it was always worst on the sides, and I´ve never seen this effect that bad on a 32", so a wild guess is just that the tubes arent powerful enough for the 36" screen?
     
  4. Squirrel God

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    Panasonic Tau tubes are actually not flat. They are curved. They then stick a flat bit of glass on the front so that they look flat.

    With this in mind, I'd say the dirty patches are caused by air, dirt or whatever seeping through between the flat panel of glass and the actual tube. I'd say it disappears over time because the whole screen becomes "dirty" thus there are no patches and the screen becomes uniformly "discoloured" (for want of a better phrase).

    My best deduction :)
     
  5. keyser

    keyser
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    Interresting theory, the toshibas are they same way aren't they, not actually flat, but have another front screen to make them appear flat? And they also suffer from the dirty screen. The more dirty screen on the sides makes sense since there would be more room there from the actual screen to the front of false flat one?

    It would be very interresting to see what manufacturers use this "false" flat screen and see if only these suffer from the dirty screen effect.
     
  6. jems

    jems
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    I get the same effect with my Philips 9616 ( Panasonic tube) but only if the screen is all white ie if I have it set to the video channel and there is no signal coming through. Then there are dirty patches and the longer you leave it the worse it gets. It does clear though and i now make a point of not leaving the tv like this and never leaving it on a white screen.
    This is what happens for me, it may be worse for other people.
    jems
     
  7. gmt steve

    gmt steve
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    I'm fairly sure that only Sony make a truly flat tube. A Sony rep once made a great show of pointing this out to me when Panasonic first launched their Tau sets. He said that a truly flat tube actually looks concave, which is true of the Sony sets. This was a couple of years ago though.
     
  8. Squirrel God

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    Philips Cybertubes are flat too.
     
  9. BillyNomez

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    Ok,thanks guys - seems its a known problem with theories as to why but anyone say for sure that it does indeed diminish over time, does the screen become uniformally good or bad ?
    How about an air blaster in any gaps - surely not !

    BNomez
     
  10. Paul D

    Paul D
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    Hi
    I actually ran into this problem with Toshibas first "true flat" screen.( I got one of the first set in the country)
    It was so bad, Toshiba actually sent their top techincal engineer to have a look.
    This led to them getting their far east processing plant to cut one of their tubes in half to check for glass thickness!.
    It turned out the "tube" factory had changed the glass thickness level changing between research and actual production models.

    From what i could gather, the tubes are one piece as normal tubes. But although the front is totally flat, the inner side is still curved. This leads to the side of the picture having thicker glass to shine through.
    One of the ways they have to combat the problem of dark banding on each side, is dynamic brightness adjustment. This actually brightens the picture each side as the guns scans from side to side etc.
    This then causes another problem in that the metal "invermask" then starts to distort due to the extra heat of the guns. This deforms the mask causing the "dirty" looking screen.
    Another side effect of the thicker glass is the "Moire" effect. This can cause weird patterns to form on either side of the screen depending on whats being shown.
    I changed to the Panasonic 36PF10 which was much better than the Toshiba, but even that suffered from some "Moire" effect and some unrelated purity issues.
    I'm glad to say that these issue are a thing of the past with the price of Plasmas falling almost by the day.
    I have now switched to a 42" Panasonic plasma and find it almost faultless. (though some people have reported they see some slight flickering)
    Watching sport now is a total pleasure as the slow pans are totally devoid of "dirty patches". Ie the grass stays the same colour no matter what part of the screen you are watching!:D
     
  11. juboy

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    Interesting, I had to change away from the Panny 36PF10 because it simply can not accept an RGB scart signal from DVD players without the horizontal banding problem.

    I switched to a Tosh 36ZD26P and the so called 'dark patches' problem is nowhere near as annoying/noticeable as the Panny branding/scrolling lines problem.

    To caveat; I have a Panny 32PF10 for use in the bedroom and it has NO banding/scrolling issues at all and is a fantastic TV.
     
  12. Paul D

    Paul D
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    My 36PF10 was fantastic via RGB from my pioneer 737 DVD player:) , ie no banding problems what so ever. I assume yours must have been a production or batch problem as quite a few of my friends also have 36PF10's without this problem.
    In fact the only problem via RGB was a slight chroma delay, which was fixed in the pioneers DVD picture settings menu etc.
    I was sorry to see the PF10 go, but the new plasma soon soothed that feeling away!:devil:
     
  13. keyser

    keyser
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    fulabeer,

    doesn´t it bother you any that on your plasma you are getting about 90 less lines of resolution than on a standard CRT?
     

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