1. Robert123

    Thread Starter New Member

    Feb 12, 2010
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    When I open my T.V. then the electricity in the house fall down and when I return the electricity in the house I discover that my T.V. Break down
    I remember that before two years this T.V. was broken and the technician replace the PTC (?) this is a box with 3 legs
    How I can know if the PTC break down ?
    Did I need to buy a special PTC only for this T.V. model or I can used other
    The name that printed over the PTC is ZEM 1 (this is not original, this is what the technician put
    Also my little son turn on and off the T.V. a lot of times
     
  2. Wendy

    Moderator

    Mar 24, 2008
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    I have not a clue what a PTC is. Anyone?
     
  3. Jony130

    AAC Fanatic!

    Feb 17, 2009
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  4. Audioguru

    New Member

    Dec 20, 2007
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    The PTC resistor is a very low resistance when it is cold then it allows a high current in the degaussing coil. When the current warms it then its resistance increases and it stops the degaussing. A TV makes a noise from the high current in the degaussing coil when it is turned on.

    The degaussing "cleans" any magnetism picked up by a CRT TV if it was moved which would cause mis-colours on the screen.

    If a CRT TV does not show a picture then the PTC has nothing to do with it unless a main fuse is blown.
     
  5. Gdrumm

    Distinguished Member

    Aug 29, 2008
    684
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    Robert123,

    Call the technician again, there is some DEADLY stuff inside a TV.

    We want you to be alive to raise your son.

    Gary
     
  6. bertus

    Administrator

    Apr 5, 2008
    15,652
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    Hello,

    The part you describe is probably the NTC/PTC for the demagnetizing of the CRT tube.
    You will hear a "dzoing" sound when an old crt color TV is energized.
    This is a current boost through coil that is mounted on the back of the CRT tube.
    When the NTC/PTC combination has done its job the current through the coil will be nihil.

    When switching on and off the TV very quickly the NTC/PTC block will have trouble with cooling down again and break afther some time.

    This is the schematic part how it is done in the k11 TV from philips:

    [​IMG]

    Greetings,
    Bertus
     
    Last edited: Feb 21, 2010
  7. Robert123

    Thread Starter New Member

    Feb 12, 2010
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    0
    Thanks for every one that wrote his comments it help me
    I have 3 questions :
    1. In the article that Jony130 give wrote that to check if the degaussing coil is O.K. then I need to check with a tester that the pressure in the two input of the degauss circuit is 3 – 4 bars
    I don't understand why this operation check the degaussing coil ?
    2. Audioguru wrote " The PTC resistor is a very low resistance when it is cold"
    Can you explain it ?
    3. bertus, I understand that in the box with 3 legs there is PTC and NTC
    What is the NTC ?
     
  8. Audioguru

    New Member

    Dec 20, 2007
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    The PTC is a "positive-temperature-coefficient" resistor. When it is cold (cool) it is a very low resistance so it conducts high AC current into the degaussing coil. The high current in the PTC heats it and its positive temperature coefficient causes its resistance to rise and reduce the current in the degaussing coil. The NTC does the opposite and it shorts the degaussing coil after a bout 10 seconds so the coil does not cause interference with the colours.
     
  9. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    I think every one is missing a point here. It seems to me that the OP is assuming because it was the PTC last time the TV was repaired, it has to be the PTC this time.

    Probably not a very good assumption.

    The power went out in the house and the set no longer functions.

    I would start with basic block diagram trouble shooting. Like does it have sound but no picture? No sound and no picture?

    With a power failure in the house, I would assume some kind of power supply issue with the set.
     
  10. retched

    AAC Fanatic!

    Dec 5, 2009
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    Also, check the outlet the TV is plugged into. Obvious, I know....but Ive spent more time on less.
     
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