Sky+ picture problem

Discussion in 'Sky Digital TV Forum' started by leighan, Oct 4, 2001.

  1. leighan

    leighan
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    I've noticed that I get a faint pattern moving from left to right every second or so, and was wondering if anyone who has Sky+ has seen it.

    The pattern quite difficult to see at first, but once noticed, it distracts me especially on a large screen. It is a a zig-zag from bottom left to top right - almost as if the contrast has changed. I first thought it was RF interference but it continues even if I remove the RF leads.

    So far I have only used the s-video output from the Sky+ box so I am not sure if it exists on the composite or RGB outputs.
     
  2. Starburst

    Starburst
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    The picture on my SKY+ through a scart cable set for RGB is excellent.
    However when viewing in another room through the TVlink I do occasionaly see a very faint diagonal line scroll across the screen.
    Mind you this was there when I used a normal digibox and I assume it's just run of the mill RF interfernce.
     
  3. leighan

    leighan
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    I've now tried RGB and composite via the scart and neither exhibit this pattern (RGB providing the best picture quality). So this problem only applies to the s-video output.

    Tomorrow I'll change the s-video cable keeping it away from any others to see if this changes anything and also check out the RF as you mentioned it.
     
  4. leighan

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    This distortion is only visiable when I route the s-video output from Sky+ through my Meridian 562v.

    Sky+ -> meridian -> TV Distortion
    DVD -> meridian -> TV No distortion
    Sky+ -> TV No distortion
    LD -> meridian -> TV No distortion

    The behavior is the same if I re-try the tests to my projector instead of the TV. It is easier to see the distortion on the larger screen.

    Now I know the Meridian is an active switch so it re-amplifies the signal. I wonder if it is showing up a fine distortion which is just not visiable in the original signal.

    I would be interested to know if anyone uses Sky+ s-video and routes through their AV Amp.

    Andy Leigh
     
  5. rdg

    rdg
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    Not quite the same, but in one place we route the s-video output of a Grundig box through a Meridian 561, and on the big screen ,it shows no problems.
    I can try the Sky+ box through the TAG AV32R but have got used to going straight from the box to the TV (RGB). It's a bit of a hassle switching between inputs on the TV, but I assume this is better.
    Out of curiosity, I once read of a product - can't remember what it was now - which apparently improved the signal if it was put through it. Something to do with buffering I seem to remember, and nothing to do with scaling. I thus wondered, this problem apart, if there were any benefits to putting a signal through a good processor?
     
  6. Chippy99

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    Hi Andy,

    I don't know about the Sky+ box as I haven't bought one (yet). But I do know that the outputs on stb's in general can be pretty poor in terms of suppressing any unwanted DC offset voltages. My Tag McLaren tries its best to help here, but even then it sometimes has problems with some stb's, where the DC voltage is so high, it clips the input circuitry on the Tag!

    I don't know if this is a similar issue, but I can't think of another reason why the picture should be distorted *only* when going through the Meridian.

    In the case of the Tag problem, this can be fixed, but its a fiddle. Why don't you ask Meridian what they think?

    Good Luck,

    Chip.
     
  7. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    I have a client with a 562v which exhibited exactly the same problem when feeding a (downconverted from RGB)svideo to his Sony TV.

    All other sources fed S/video through it were fine except Sky.

    Gordon
     
  8. leighan

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    Chip,

    I checked with Meridian and they also believe this behavior is because of DC on the input signal from the Sky+.

    Richard,

    It would be interesting to know if it causes the TAG to clip. I see the main advantage of routing the cable through a processor is flexibility of control where the signal is sent, but also driving the cables properly can have an advantage if over a long distance like to a projector.

    Gordon,

    So I'd better not bother with down converting RGB unless I use something which can effectively remove DC from the signal.

    So, does anyone know how DC gets in the signal?

    Andy Leigh
     
  9. warne

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    I get exactly the same thing - it's most noticeable when there's a lot of consistent colour in the picture, like when watching a football match. However, mine even occurs when watching a DVD! , although the effect is barely noticable - it's most obvious while watching Sky.
    I too run a TAG set up, but to a Loewe TV, all of which I've had checked out. I also have some low-level hum from the power amps (and especially the subwoofer) - again, no matter what I try regards swap testing, earthing, recabling makes any difference.

    I've come to the conclusion it's all caused by "airborne" electromagnetic interference. We get our mains from a transformer which sits up a pole a few yards away, via above ground cabling.
    Do you happen to have anything like this in the vicinity?
    I was thinking of getting the electricity board round to check it out, but I'm not sure if they'd replace several thousand quids worth of transformer just 'cos "some prat's getting slight interference on his high end AV system"! :rolleyes:
     

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