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Green G2 levels on BG800.

Discussion in 'Projectors, Screens & Video Processors' started by bxd, Feb 5, 2003.

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  1. bxd

    bxd
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    Hi everyone,

    I seem to be having a bit of an issue with setting the Green G2 levels on my BarcoGraphics 800.

    If I follow Rolands suggestions on doing this :
    _______________________________________
    Find a black bit of film and pause it.
    Turn the contrast and brightness down to 0.
    Look into the lenses and adjust each pot until the raster just starts to glow and make sure each is the same intensity.

    A properly set up barco with a good source at the correct output level will have brightness at 40%ish and contrast at about 70-75% (if it starts squeeling turn the contrast down a bit.
    _______________________________________

    If I do this (assuming I'm doing it correctly*) and then display a greyscale (e.g the Avia crossed greyscale), I seem to end up with a situation where the green tube seems to be too bright (raster and retrace(?) lines are visible). The other tubes seem OK. If I turn down the G2 (until the raster disappears) I can't then get a good balance with the other tubes and greyscale loses most of the black detail.

    I'm begining to suspect that something 'other' than the green G2 control is the cause of this.

    Is there another adjustment on the neckboard (or elsewhere) that would affect the G2 ?

    Any suggestions ?

    Brian.

    (* I hope that Roland can find some time for crt school in the near future)
     
  2. Roland @ B4

    Roland @ B4
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    Swap the RGB amplifiers over there are some adjusters that some one may have had a play with.

    Also check under picture tuning that the colour balance has been set correctly and no settings are too high throwing every thing off.

    Best way to do colour on something like a Barco800 is to take the colour out of the source by reducing the satuaration. then set it up to virtually a B&W picture. If that is neutral then the rrest will follow.
     
  3. bxd

    bxd
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    Roland,

    Thanks for your suggestions.

    I changed the RGB amplifiers around (should have thought of that myself !!) with no real change..... I'm still seeing retrace (?) lines and the background is still too bright.

    Where to next ?

    I'm not sure about your reference to "picture tuning". Is that a menu item on the G800, or are you just talking about the colour control ?

    I always do a set up with the colour (and tint) down at zero. I don't have a decent pal dvd source so I'm using ntsc on a Sony 7000 dvd player which will display below black.

    Brian
     
  4. Roland @ B4

    Roland @ B4
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    Brian
    It's been a few weeks since I played with an 800 so I can't remember the exact lay out. Hit the adjust button on the remote and selet Random Access,
    use the Selected Source
    then I thought the top item was Picture Tuning but this is where the old grey matter is letting me down. it may be refered to as colour balance where you have 3 presets 3200,6500,9200 and one custom. It's the custom setting for black probably called cut off. It could be that one colour is being set really high.

    After that I would just turn the G2 pot down untill you just can't see the flyback and raster illumination.
     
  5. bxd

    bxd
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    Roland,

    I only managed a brief look last night but I don't seem to have the option for 'picture tuning' on my G800 (software version is V2.04), perhaps you're thinking about another machine.

    I'll have another look sometime next week.

    Many thanks for your help.

    Brian.
     
  6. bxd

    bxd
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    Roland,

    Having eliminated the rgb amplifiers, I was wondering about swapping around the crt neck boards to see if that's the source of my BG800 problems.

    Looking at the service manual, I see that the green crt socket (part 76 17595) is slightly different from the other two sockets in that it has a 150K resistor (R3) on the circuit.

    Is it OK to swap this board over to one of the other tubes or should it be kept on the green?

    Many thanks,

    Brian.
     
  7. Roland @ B4

    Roland @ B4
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    I think you are safe to swap them about.
    It might be worth moving the EHT and focus leads round too. but this sound more like a tube now.
     
  8. bxd

    bxd
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    Roland,

    Thanks for your comments, I'll give it a try.

    Bit of a bummer if it's the tube !! ........ I may well have to talk to you in your professional capacity !!

    Might try and catch you in Bristol on Saturday.

    Brian
     
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