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projection tv

Discussion in 'Electronic Repair' started by goPostal, Sep 11, 2007.

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  1. goPostal

    goPostal Guest

    Not to take too much of your time, here's what happened:

    I took my magnavox projection tv rear off to clean the guns and the mirror.
    While wiping it out I hit the color adjustment knobs in the back. I tried to
    "fix" it and obviously it got worse. Is there a "trick" to setting the
    colors? I got pretty close by trial and error, but there is too much yellow
    and skin tones are crappy. I've googled this to no avail. Is there a set way
    to adjust the gun's colors to get it right? This is inside, not the color
    adjustments via the remote menu, just to clarify.
    Thanks to all in advance and for reading this far.
  2. Guest

    Trick is to set the brightness at factory default, usually 50%. Then
    turn down the color all the way. Recieve normal video and cut the
    picture control down until you can just barely see the picture, then,
    if you have to do it in the back look at the lenses, or their
    reflections in the screen. Try to equalize them at a barely seeable

    When you have the room dark and have a dark picture that looks pretty
    much black and white, that is not overly tinted, then turn the picture
    control to maximum. Note the color of the bright parts of the picture
    at that time. Then you need to turn down the drive control for that
    color. It could be a pot or it could be in software.

    Just what year is this thing and what make and model ? And where are
    you geographically ? Not that I'm coming over, but I want data on what
    kind of different repairs are needed more often in different

    It is very possible that your blue tube has bad coolant. Red plus
    green plus blue make white, take the blue away you have yellow. Very
    common in certain brands. Also in certain brands the blue is pushed
    alot harder.

    In Sonys especially, the blue is the hardest driven tube in it, and
    the reason is that they use a different phosphor. It is not as
    efficient, but it emits a very deep, pure blue color, somewhat like
    comparing sky blue to midnight, or Navy blue. It is a deeper, truer

    Like I said, what is the make and model of this thing ? Without that I
    can go on for hours but there is no point.

  3. There are normally two sets of adjustments -- Screen and Drive. Broadly
    speaking, the Screen control adjust the darkest areas of the picture, the
    Drive the brightest. (There is usually no red Drive control, because the red
    phosphors are/were the least-efficient, and were run "at full blast".

    Looking at a monochrome image (play "Casablanca"), you need to adjust these
    controls to get a neutral (colorless) image.

    Try Googling "gray-scale tracking" + "crt".
  4. goPostal

    goPostal Guest

    Thanks for replying double Z. Here's my model:
    It's a 51 inch magnavox. I know the blue gun is going bad as the picture has
    a blue offset in the lower left and opposite right top corners. The color
    was fine and after being unable to fix the blue via remote so I figured a
    little cleaning wouldn't hurt. I carefully wiped out the dust in the back. I
    hit one of the guns color knobs though and knocked the color a little off
    (to this point it was fine). I thought I'd just twiddle it back to where it
    should be and it's one of those things that just gets worse the more you
    "fix" it.
    As to the coolant, it looked quite clear looking into the guns, but I was
    surprised how dusty and filthy the inside of those things get. It should be
    more user serviceable if it funks up that fast. (and we are clean people
    with no animals too)

    BTW I'm in coastal Pacific Northwest. You ever pass down 101 along the coast
    and I'll treat you to the best crab and clam you'll ever eat.
  5. goPostal

    goPostal Guest

    That makes sense because my black and white color is screwed up too. It's a
    weird brown/grey. Tonight I'll get the info and get cracking. Thank you!!
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