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Brightness adj on Sony WEGA

Discussion in 'Electronic Repair' started by Mike, Dec 9, 2003.

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  1. Mike

    Mike Guest

    I just purchased a new Sony WEGA TV (model KV24FV300) and am having some
    problems with the black level and dark grays. It seems that the TV is
    chopping dark grays below around 10.5 IRE. At first I thought I could fix
    this with the brightness control, but even setting the brightness range to
    63 in the service menu and then turning the brightness all the way up, only
    produces a dark gray instead of black. I then decided to play with the
    Picture (contrast) control, which opens up the blacks a little bit.
    Unfortunatelly, I have to increase the Picture to ridiculous levels (i.e.
    to the point of blooming) to see details in dark gray areas and to see the
    slightly lighter than black bar in the PLUGE of the SMPTE test pattern. It
    appears that the control I really need is to raise the 50% gray level
    higher so that there are more gradations in the dark areas. Doing this
    using the Picture control to expand the dynamic range, unfortunatelly also
    raises the white level, which I do not want to do due to blooming. I want
    to keep the white level the same and just raise the middle gray point so
    that the brightness curve has more slope in the dark areas, since it
    currently appears to be completely flat upto something like 10.5 IRE (i.e.
    the lighter than black stripe in the PLUGE). Any advice would be
    appreciated. I am sure there is a service mode option that can be tweaked
    to increase the amount of gradations in the dark grays, I just don't know
    what it is.

    Thanks,

    Mike
     
  2. john

    john Guest

    Let me get this right..
    You have just purchased a New Sony Vega
    and you are already into the Service Menu,s.
    If the TV which obviously does not meet
    your specs why not return it for another.

    kip
     
  3. Mike

    Mike Guest

    Because it is perfect in every respect other than the simple fact that I
    want to open up the dark grays a little by moving the 50% gray point up in
    the brightness scale, which I bet is a simple service menu single parameter
    change. I just don't know which parameter that is. No TV is perfect. I am
    quite happy with this one.

    Mike
     
  4. Jerry G.

    Jerry G. Guest

    Without the exact service manual, it would be hard to tell you the exact way
    for your set. Being a new set, I would call the dealer to find out the
    authorized service rep for it, and ask them to come out and adjust it for
    you.

    Do you have a grey scale test patter from the proper test generator to make
    sure that the set is correct or not? If you are watching a station through
    a cable or sat service, you have the provider that runs their signals
    through various equipment, plus you have the box feeding the set. You can
    also look at the demodulated feed in baseband that is feeding the set with a
    scope to make sure that the input signals are good before touching any
    adjustments. The adjustments should be done with the proper grey scale test
    pattern. Going by sight from an unverified source is not the way to set up a
    set!

    --

    Greetings,

    Jerry Greenberg GLG Technologies GLG
    =========================================
    WebPage http://www.zoom-one.com
    Electronics http://www.zoom-one.com/electron.htm
    =========================================


    I just purchased a new Sony WEGA TV (model KV24FV300) and am having some
    problems with the black level and dark grays. It seems that the TV is
    chopping dark grays below around 10.5 IRE. At first I thought I could fix
    this with the brightness control, but even setting the brightness range to
    63 in the service menu and then turning the brightness all the way up, only
    produces a dark gray instead of black. I then decided to play with the
    Picture (contrast) control, which opens up the blacks a little bit.
    Unfortunatelly, I have to increase the Picture to ridiculous levels (i.e.
    to the point of blooming) to see details in dark gray areas and to see the
    slightly lighter than black bar in the PLUGE of the SMPTE test pattern. It
    appears that the control I really need is to raise the 50% gray level
    higher so that there are more gradations in the dark areas. Doing this
    using the Picture control to expand the dynamic range, unfortunatelly also
    raises the white level, which I do not want to do due to blooming. I want
    to keep the white level the same and just raise the middle gray point so
    that the brightness curve has more slope in the dark areas, since it
    currently appears to be completely flat upto something like 10.5 IRE (i.e.
    the lighter than black stripe in the PLUGE). Any advice would be
    appreciated. I am sure there is a service mode option that can be tweaked
    to increase the amount of gradations in the dark grays, I just don't know
    what it is.

    Thanks,

    Mike
     
  5. Jeff Wiseman

    Jeff Wiseman Guest

    Exchanging it for another won't necessarily fix it since most of
    these come with screwy factory defaults. These sets can be made
    to look much better with a little care. For example, the Sonys
    all seem to have a "red boost" setting that is turned on from the
    factory. This looks really wiz-bang in the store but makes it
    near impossible to get good full latitude color adjustment unless
    it is turned off.

    Anyway, to the original poster, check to see if there is a Y-DC
    (DC trans ratio switching) register in your service menu. If I
    remember correctly, many of the earlier flat screen trinitrons
    could have their black level improved by turning this off (i.e.,
    changing it's default of "1" to "0"). This actually darkens the
    absolute black level on the screen which in the original poster's
    case MIGHT add the extra latitude that he wants in the grey
    range. It's easy to change back if it doesn't work so it might be
    worthwhile to try it out.

    I have a 36XBR250 that I've done this with and I love the rich
    blacks that it gives relative the the fairly grey blacks that it
    came with from the factory.

    - Jeff
     
  6. Mike

    Mike Guest

    I've tried with an SMPTE pattern that is provided on a channel by my cable
    provider (no cable box in use) and I have a DVD with a test pattern. Both
    show the grays near black to be compressed so as to be indistiguishable.

    Mike
     
  7. Mike

    Mike Guest

    Thanks for the tip. I'll see if I have the Y-DC offset and will try
    toggling to see if there is an improvement. I'm less concerned about the
    red boost, since I only seem to notice it in the SMPTE bars, for now. I'm
    more concerned with the loss of detail in the 25 IRE to black tones,
    since it really makes dark scenes look way too dark.

    Mike
     
  8. Are you using a pattern generator or a test disc on a dvd player? If the
    latter you may not have a player capable of producing proper blacks. not an
    uncommon scenario.

    Leonard Caillouet
     
  9. Mike

    Mike Guest

    I am using both methods. A cable TV generated signal and a DVD based one.
    They are in accord, so it's the TV.
     
  10. xrongor

    xrongor Guest

    no tv comes adjusted well from the factory and no amount of returning it
    will help.

    randy
     
  11. Mike

    Mike Guest

    After cycling through the service menu twice last night I finally found
    what I was looking for. The latest crop of Vega TVs has a VP1 group in
    the service menu which contains a lot of "interesting" things that can be
    set. The setting that fixed my dark grays are black problem was the SBRT
    setting, which was set right in the center at 32. I had to increase it to
    50, to basically make the TV perfect as far as black level adjustment
    goes. Also, in the VP1 group I discovered individual on/off controls for
    the red, green, and blue guns. Using these you can perfectly adjust color
    and hue, by shutting off the red and green guns while viewing SMPTE color
    bars. I can't remember the setting acronyms, but they are quite obvious.
    There was no Y-DC setting anywhere, so I couldn't turn that off. After
    adjusting the geometry settings (there was a huge amount of overscan
    which I reduced and miscellaneous bad geometry which I corrected) last
    night, and with the brightness fixed, this TV is awesome!

    Just goes to show that perseverence pays off.

    Mike

    Note:

    To enter the service menu, you use this combination on the remote while
    the TV is off: Display, 5, Vol +, PWR

    To save your changes: Mute, Enter

    To get the TV out of the service menu, simply shut the TV off

    WARNING: Changing settings in the service menu can permanently damage
    your TV and will most likely void the warranty. Do so at your own risk!


    Keywords, so that other people with a similar problem can find this
    message:

    Sony KV24FV300 WEGA dark tones brightness picture gray black service menu
    PLUGE SMPTE
     
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