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How much geometry distortion is acceptable?

Discussion in 'TVs' started by kenfowler3966, Sep 23, 2001.

  1. kenfowler3966

    kenfowler3966
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    You have a misconception if you think flat screens = better geometry. In fact it is incredibly difficult to achieve good geometry as the distance from the guns to the screen keep changing as the beam traverses the tube, and complicated adjustments are required to keep it a straight line. In a curved screen these effects are reduced by a more constant distance in all planes.

    I understand that geometry errors of up to 5mm are considered acceptable on setting up sets in the factory. My set has a straight bottom line, the top curves down to the centre then back up again and both sides are slightly curved, but all well within the 5mm. You only tend to notice if the picture is smaller than the tube face, I prefer to zoom out so that it is no longer seen.

    I did notice in some of the coverage of the recent terror attack that lines which should have been vertical on news programs were very curved inside the picture, but realised it was the lens used on the cameras to get the view width required. IE it could be errors in the recording rather than your tv that you notice as well.
     
  2. mr_wriggly

    mr_wriggly
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    I recently bought a Panasonic TX28PK2 television from John Lewis. Since I first switched it on I have noticed that the top right hand corner of the screen image bends inwards, for want of a better description. Since the tube is perfectly flat I had expected near-perfect picture geometry.

    Straight vertical lines on the right hand side of a picture deviate by about 6mm from the bottom to the top of the screen and i've got to the point where i can scarcely concentrate on anything else while watching it. Since I watch terrestrial broadcasts in 14:9 mode with black bars down the sides of the screen (as i can't stand stretched images) this is a major annoyance.

    What i'm trying to ask, albeit in a very round-about way, is whether this much distortion is within acceptable limits on a £700 TV. I'm tempted to call out an engineer or get a replacement,but it would be a lot of hassle if i couldn't gain anything from it.

    Thanks in advance
     
  3. dAvE6

    dAvE6
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    thats a very good question. i had the same with a 28pk3 tv from panasonic too. unfortunatly there will always be some. it was about what you described, so they took it back and tried to fix it. it came back a little better but it wasnt perfect by any means. i suggest you do ask them to have a look at it (if its free) and see what they can do. but dont worry they cant make it WORSE. if they do then demand a new set.

    14:9 is the most wobbly shape anyway. stretched images arent that bad, man.
     
  4. Mr.D

    Mr.D
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    You may be able to improve things in the service menu I did a big post on this with reference to the PK1: the principles if not specific service menu designations will apply to most CRT TVs.
     

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