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Toshiba 329P8M Vertical Linearity Problem (Help!?)

Discussion in 'Electronic Repair' started by Bruce Dow, Jun 12, 2006.

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  1. Bruce Dow

    Bruce Dow Guest

    There is no year indicated on this TV anywhere. It is a nice 32" with
    Surround Sound.

    The vertical linearity has become so poor now that it is no longer
    watchable, but otherwise the TV is great.

    There is a black band at the bottom of the screen and the bottom
    half of the picture is all squished.

    I read the user manual and there is no mention of the vertical
    linearity. I took the back off of the set and there is no vertical
    linearity control there, so I assume that it must be adjusted in
    Service Mode.

    I did a web search and found a couple of ways of entering Service Mode
    and tried them, but they didn't work. (The one where you press Mute
    three times then hold down Mute and press Menu? There is no Menu on this
    TV.) (The one where you hold down 9 and press Channel Down? Didn't
    work.) (There was another one: Hold down F and press Right Arrow
    pointing into a Circle and enter 1046. Didn't work either.)

    Please let me know if you know how to enter Service Mode on this set or
    how the vertical linearity should be adjusted.

    Thanks,

    Bruce
     
  2. Arfa Daily

    Arfa Daily Guest

    The vertical linearity should not be adjusted - at this point in the game,
    at least. There is a fault in the field output stage. This will almost
    certainly be a defective electrolytic capacitor, particularly if the problem
    has been getting progressively worse. Once this has been located and
    replaced, there will probably be no need to carry out any adjustments.

    If you don't have experience working on TVs, I would strongly recommend that
    you take it to a reputable repair shop, as the power supply circuitry
    employed in TV sets, is potentially LETHALLY DANGEROUS.

    If you are OK with the safety angle, look for caps close to the field output
    chip's heatsink. Replace them all if you don't have the necessary test gear
    to check them properly.

    Arfa
     
  3. Some, if not many vertical deflection circuits use a push-pul
    oscillator setup. One side may have failed I agree to check for ba
    caps. If you do replace, try to find the same µf rating with a large
    case/higher voltage, if the PCB layout allows it. Be sure you sta
    within the same error tolerance. This will put a beefier component t
    possibly patch a circuit weakness

    Another thing to look for is the deflection yoke, or it's control
    While the yoke rarely goes bad, they do from time to time. Top an
    bottom deflection should be more or less equal, so if you can isolat
    the upper coil set from the lower, be sure they are recieving prope
    voltage. If not, the output can be hampered by a variety of issues
    but think simple. I have run into a similar problem which was fixe
    by simply repairing a bad solder joint for the yoke's plug on th
    PCB. Any discoloration of the windings is an extremely obviou
    problem

    What you likely have is a bad component, not a faulty adjustment
    Adjustments go out of shape very gradually as a result of wear. A
    instant failure or a rapid one indicates a component fault. Forge
    your TV's internal modes because even if you did find it, you wil
    not find such an adjustment

    Service mode simply kills vertical deflection for aligning guns
    adjusting color drives/chroma, and miscellaneous troubleshooting. Al
    service mode will give you is your entire picture compressed to
    single horizontal line on the screen. This is not what you ar
    looking for

    If you aren't proficient with electronics, take it in to be repaire
    instead of meddling with controls that are already properly set. On
    does not tweak-out the base vertical size adjustment to make up fo
    vertical collapse
     
  4. Papa_J

    Papa_J Guest

    Also: An ESR Meter will assist you is checking the capacitors in the
    Vertical and Supply Circuits, replace the ones that check deficient.
     
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