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CRT Raster Query

Discussion in 'Projectors, Screens & Video Processors' started by Oakdene, Aug 22, 2004.

  1. Oakdene

    Oakdene
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    Dear CRT forum members.

    I have a Barco Cine8 which I am trying to install as per the manual. I am getting nowhere with setting up the raster correctly and I am getting confused. I have reset all parameters to midposition including the astigmatism and deleted all blocks.

    The problem is that the raster seems too large for the phosphor area and consequently goes outside the area. Shifting it up/down or left/right does not help - it is too large! (I have a photo to illustrate if anyone would be interested showing the corner down left going beyond the phosphor area).

    What could be the problem? I am lost.

    Grateful for any help.

    Best regards

    Dan Hoij
     
  2. ufitsy

    ufitsy
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    I am as new as you to this - is there any blanking on?
     
  3. Oakdene

    Oakdene
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    No, I have made sure that blanking is off. Thank you for your try.

    Regards

    Dan
     
  4. L3gion

    L3gion
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    How bad is the overlap? I ask because when centering the raster on my 708, I cannot achieve what might be called perfect centering.
    It's as if the raster is almost too large for the phospor, and so I get a tiny amount of overlap on the corners.....and just shifted it around so that its minimal. Rather like trying to position a square in the optimum position inside a trapezium.

    It seems to have worked ok as my image doesnt come near those borders when a source is being used.

    I hope that shed a little light on the problem

    Jas
     
  5. Oakdene

    Oakdene
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    Jas,

    Thank you for your reply. It sounds like your situation is very similar to mine. Perhaps the real world is different to the ideal situation and perhaps the difference is nothing to be concerned about. However with it being emphasised as detrimental to the projector and in conflict with all advice given it is still a bit odd.

    Regards

    Dan
     
  6. Lux In Umbra

    Lux In Umbra
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    Prefix: I'm pretty damn new to this too!

    I found that I couldn't completely remove the raster from the edges when setting up my 708. Particularly the outer extents of the genlocked grid. Much worrying later (and wondering why there are only raster movement - not raster size - adjustments) I found that once the actual raster used for the source is used, its well within the tube bounds.
    (I also initially panicked at the warm-up white screen - thinking "Holy !*%^ - has this thing previously been set up for use in an igloo!?"... before working out that the whole tube is supposed to be used. {Appears a little too overscanned here too, so I quickly exit warm-up!})
    So, you might hopefully find that things look better once you've got to the later stages of the set-up.
     
  7. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    If you are worried about overheatng the tube seals by going close to the edges with the raster then don't. Just make sure the ACTIVE picture area is not close to the edges of the tube.

    In an ideal world the raster would be centred pn each tube then the image would be centred on each raster. In your case I'd do your best with first then make sure second is adhered to.

    Gordon
     
  8. Oakdene

    Oakdene
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    Gordon,

    Thank you for your input. I am coming to the conclusion that I should not be concerned about this raster overlap but also that there is nothing I can do about it. I will just have to accept that the raster is overdimensioned. Is that correct?

    Regards

    Dan
     
  9. Oakdene

    Oakdene
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    Gordon,

    Thank you for your input. I am coming to the conclusion that I should not be concerned about this raster overlap but also that there is nothing I can do about it. I will just have to accept that the raster is overdimensioned. Is that correct?

    Regards

    Dan
     
  10. Godfather

    Godfather
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    After reading this thread I had a look at my Cine 7LT's rasters last night and was happy to find that they were all perfectly centered within each tube face. I can't believe they got it wrong on a Cine 8. Aren't there adjustments that can be made to over come this Gordon?
     
  11. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    I'm sure there are raster centreing adjustments but I've not done lots of Cine series PJ's so can't remember off top of my head.

    Don't confuse the image with the raster. For best optical clarity and to prevent overheating of the seals you want the IMAGE to be centred on the tube face. It's pssoible to do this with a non centred raster. To see the raster put up a 0ire window pattern on the PJ then turn down contrast to 0 and turn up brightness high and look in tube face. You should be able to see the lit active raster. Obvously make sure you note the correct contrast and brightness settings before doing this so you can put it all back as it should be afterwards.

    Ideally everything should be centred of course. Although in some cases the raster gets moved to the left and image to right to stop ringing on left edge of picture with some PJ's.

    Gordon
     
  12. Oakdene

    Oakdene
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    Thank you for your help

    Regards

    Dan
     
  13. Roland @ B4

    Roland @ B4
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    The main reason for centreing the raster is to keep all the electrical adjustments to their minimum settings thus preventing areas of the projector being overdriven. Barco seem to have a particular obsesion with it in their manuals and this mainly comes back to the cross hair whcih is used for toeing in the lenses.
    Some projectors will centre up beatifully and then not display a picture centrally.
    If a projector has had a tube change at some stage the settings done in the factory when it was built can be quite a way off with the new tubes.
    I go with the keep the active picture off the edges school
     

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