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Correct way to set up raster geometry?

Discussion in 'Electronic Repair' started by HandyMan, Oct 17, 2005.

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  1. HandyMan

    HandyMan Guest

    Hi everyone,

    Have a Philips 28PW6517/01 here. To cut a long story short, I
    accidently reverted the set to default values for just about everything
    by accessing the SDM (Service Default Mode).

    The raster now needs some serious attention. There are many available
    settings and although I can manage to increase the vertical and
    horizontal width without any trouble, I cannot get the sides of the
    raster straight. EW pincushion control, trapezium control, upper and
    lower corner control, etc... so many alterable settings and changing
    one seems to be similar to changing another, with the edge of the
    screen still looking like a lock of curly hair.

    Is there a proper method, or a guide on the net somewhere which gives
    an order to do them in and what you're looking to achieve with each
    setting?

    Problem is that when you alter one, you can't get the raster right as
    other settings need altering, so you're decision on how to alter it has
    nothing much to go by, because it still looks a mess however you alter
    it as another setting needs changing. You change that other setting
    only to find it still doesn't improve matters much so you assume the
    other setting needs tweaking more, and so on... If I alter the
    pincushion, how can I know where to leave it set to since there are
    also lower and upper corner curvature settings which do similar things
    to the pincushion... it's a nightmare!

    Please can someone help?

    Many thanks,
    James
     
  2. Art

    Art Guest

    Hopefully you have a friend that has a signal generator that you can hookup
    and adjust the geometry. otherwise have a service technician do the
    appropriate adjustments for you and pay for the services. Tell them exactly
    what you did to fubar the set.
     
  3. Alain Beguin

    Alain Beguin Guest

    Art a écrit/wrote/schreef le/on/op 17/10/2005 H. Ignaas ;

    Absolutely, this is not easy do do correctly, even for a qualified
    service tech :)

    Also, be sure that the optioncodes (sticker on the picture tube) are
    correct! The are often altered by a discharge in the tube...
     
  4. You need a test pattern generator to display the correct pattern as
    specified in the service manual. You probably won't get away with this
    repair without the correct manual.
    Than you need to adjust all of the settings in the correct order.
    The service manual will tell you which pattern to use and what order to
    use when performing all the adjustments.
    This will prevent some settings from affecting others when done step by
    step in the correct order.
    That's why the service menu is hidden from the general public. You made
    a simple but common mistake by not realizing that default setting meant
    EVERYTHING would be set to default, including all the geometry settings.
    Normally you set all the physical adjustments such as yoke position,
    purity rings and magnets, etc. to the best possible picture, then adjust
    all the service menu settings, so assuming you haven't moved any of the
    internal physical adjustments, you just need to follow the correct
    procedure now.
     
  5. James Sweet

    James Sweet Guest

    I've used a PC with video out to display a test pattern on TVs, it's not
    ideal but it's close enough to get it to a point that you can use a
    calibration DVD to finish it up. It's a major excercise in patience though.
     
  6. Asimov

    Asimov Guest

    "James Sweet" bravely wrote to "All" (18 Oct 05 03:58:39)
    --- on the heady topic of "Re: Correct way to set up raster geometry?"

    JS> From: "James Sweet" <>
    JS> Subject: Re: Correct way to set up raster geometry?
    JS> Xref: core-easynews sci.electronics.repair:345565

    JS> I've used a PC with video out to display a test pattern on TVs, it's
    JS> not ideal but it's close enough to get it to a point that you can use a
    JS> calibration DVD to finish it up. It's a major excercise in patience
    JS> though.


    BTW, the Nemo dvd has nice test patterns.

    A*s*i*m*o*v

    .... If you don't know what leever "A" does then you better leever "B"
     
  7. Art

    Art Guest

    IMHO he has advanced to Lever G {Goofed Up}!! Hopefuly he has the
    equiptment and knowledge, plus a good phone line to Phillips.
    "James Sweet" bravely wrote to "All" (18 Oct 05 03:58:39)
    --- on the heady topic of "Re: Correct way to set up raster geometry?"

    JS> From: "James Sweet" <>
    JS> Subject: Re: Correct way to set up raster geometry?
    JS> Xref: core-easynews sci.electronics.repair:345565

    JS> I've used a PC with video out to display a test pattern on TVs, it's
    JS> not ideal but it's close enough to get it to a point that you can use a
    JS> calibration DVD to finish it up. It's a major excercise in patience
    JS> though.


    BTW, the Nemo dvd has nice test patterns.

    A*s*i*m*o*v

    .... If you don't know what leever "A" does then you better leever "B"
     
  8. ray13

    ray13 Guest

    If this is a newer set you need a pattern overlay that tapes to the
    screen. The gererator is built into the set. All adustments are done in
    the service mode. Which requires the service code being entered via the
    remote control. Once you have the overlay it's a piece of cake.
     
  9. HandyMan

    HandyMan Guest

    I have the correct service manual and have also been in contact with an
    acquaintance who works in the Philips tech department. The set requires
    a pattern generator, it cannot display its own pattern. The nature of
    the procedures for setting up the geometry mean that perfection is
    unattainable, and trying to follow the procedures in the service manual
    is not easy; although it shows an order (presumably the order in which
    to do the adjustments) it does not explain them well. It refers to
    three of them in almost the same way - as adjustments for straight
    vertical lines in the middle of the screen, when in fact they alter the
    geometry in a different way. The main problem is not my ability to set
    up geometry so much, but the problem of whereby I can get the left side
    perfect, but the right side remains wavy, and since each adjustment
    does both sides at the same time, you ruin one to get the other better,
    and in this case the right one seems to have a permanent geometry error
    in the lower right portion which is not correctable by the limited
    adjustments.

    Others seem to think I am aiming for perfection which is unattainable
    with today's cheaply built, relatively poor quality goods. As an
    example, an untouched 34" set only a few years old was pointed out to
    me. It was suggested I study that screen as carefully as I am studying
    the one which I'm setting up, since I was reminded that nobody else
    would pay as much attention as I am at this point. Interestingly,
    although I've watched programmes on that set many times, I never
    noticed the relatively poor geometry (amongst other anomalies such as
    purity and convergence imperfections). The horizontal borders on
    widescreen images are not level, but are bowing slightly, and the line
    tilts to the right. As for EW distortions, it probably has them but the
    raster width is set high enough to hide them off-screen and since I
    haven't bothered to get a test pattern into it, no one can be sure how
    slight or expansive such distortions may be.

    Some of the problem seems to be down to a VDR (varistor) on the CRT
    base (coupling dag coating to ground) which got cooked before I
    replaced the shorted-winding LOPTx. I hoped it had survived its
    roasting, but it's listed as a known cause of width distortion and
    altering raster size with brightness changes (which the set also has
    right now). Thing is, I can't find a supplier for the part yet. It's
    simply listed as 1mA/50V max 125V in the service manual...
     
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