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Mystery component in Sam's PhotoFact

Discussion in 'Electronic Basics' started by j, Feb 22, 2007.

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  1. j

    j Guest

    There's a schmatic symbol in Sam's PhotoFacts # 2908 and 2753-1
    (covering JVC TV sets av-2749s, av-2759s, and av-2779s) that I don't
    recall ever having seen before. It's NOT listed in the parts section
    so I have no original or replacement numbers for reference.

    Here's my attempt to describe it for those without access to the
    PhotoFacts that I mentioned. It looks like a circle with a vertical
    line running through the middle. On the upper left half of the circle
    there's what appears to be a "black pie" section extending from a
    point in the middle of the circle with an angle from about 11 to 12
    o'clock. It almost touches the circumference. On the lower right half
    of the circle there's a simular "black pie" section, with an angle
    from about 5 to 6 o'clock. There's no line where the two "pie
    sections" meet so it doesn't appear to be some sort of dual diode
    device. It also isn't a spark gap.

    If anyone knows what it is, please let me know. I have researched
    electronic schematic symbols on the web and in books but have not
    found the symbol or what it represents.
     
  2. Jamie

    Jamie Guest

    irradiation sensor?
     
  3. Phil Allison

    Phil Allison Guest

    ** Grope alert ?


    ** It wouldn't have hurt you to say where in the schematic the symbol
    appears.




    ........ Phil
     
  4. j

    j Guest

    I apologize for that omission. It's in the grid (G1) circuit of the
    CRT.

    Perhaps a circuit description would help for those who don't have
    access to the PhotoFacts I mentioned. It starts out with a 200 Volt
    DC source connected to a 1 M ohm Resistor. A 10 uF cap is connected
    in parallel with the R. The other side of the R is connected to the
    anode of a 1N4007 diode, whose cathode is connected to ground.
    Connected in parallel with the diode is the mystery component. Also
    connected to the anode of the diode is a 1k ohm R, whose other side is
    finally connected to the spark gap and grid of the CRT.
     
  5. Phil Allison

    Phil Allison Guest


    ** Err - what does it look like ??

    Any labelling

    What colour is it?



    ...... Phil
     
  6. Lionel

    Lionel Guest

    Are you 100% sure about that? - Because your description sure sounds
    like one of the most common symbols for a spark gap. Given that you
    say it's on a TV schematic, if it's on the neck-board you can be
    certain that it's a spark gap. (Less likely, it might be a gas-filled
    spark arrestor, which is sometimes used for the same purpose, but the
    usual symbol for them is two horizontal bars with a circle around
    them, & a big dot inside the circle.)

    If it is a spark gap, & you can't find it on the PCB, it might be just
    a really narrow slot cut into a big pad on the PCB, which is a trick
    I've seen used sometimes on really cheap TVs & CRT displays. Another
    odd looking variety is a rectangular block (a little like an old
    fashioned bakelite capacitor) with a very narrow slot cut into it.
     
  7. Phil Allison

    Phil Allison Guest

    "Lionel"

    ** Darn YOU !

    You beat me to the punch line !!!

    The alleged mysterious " component " is not in the BOM - simply because
    it is printed on the PCB !!




    ........ Phil
     
  8. Lionel

    Lionel Guest

    Ah. Betcha it /is/ a gas-filled arrestor. Do you have access to the
    PCB, or a photo of it? If so, look for a tiny glass cylinder with
    metal disks at each end, either with leads coming out of the disks, or
    it'll be sitting in a plastic holder, soldered into the PCB.
     
  9. Lionel

    Lionel Guest

    <grin>

    Good to see I learned something from all those years I spent salvaging
    parts from TVs & suchlike as a kid. ;)
     
  10. j

    j Guest

    To Lionel and Phil:

    I'm 99% sure it's not a spark gap. The Photofact symbol for a spark
    gap has remained the same since at least 1981 and they print the words
    "spark gap" next to each symbol on the schematic. You mention a gas-
    filled spark arrestor but your description is way different than mine
    from a 1991 Photofact schematic. In addition the device is not
    directly connected to the grid (G1) of the CRT, it goes thru a 1k ohm
    resistor first.

    Stay tuned. I'll provide a physical description next.
     
  11. Lord Garth

    Lord Garth Guest

    Can't you scan it and post the image to A.B.S.E?
     
  12. JeffM

    JeffM Guest

    Rather than using the selfish and inefficient multi-posting technique
    http://groups.google.com/groups/sea...awEp1Wot8mUGa9h3i3SmjGmAJbX05nZ-8fQ&scoring=d
    it's time you learned to cross-post.

    The last half of this thread
    http://groups.google.com/group/sci....ups+*-*-*-*-two-groups-*-*-aren't-*-different
    explains how and why.
    The last post in that thread hints at
    why multi-posting is so reviled by the majority of Usenet readers.

    The concise version:
    http://en.wikipedia.org/wiki/Cross-post
     
  13. j

    j Guest

    Note: I'm trying to cross-post this to sci.electronics.repair, hope
    it works. If not, I'll try to post the info that's there, over to
    here.

    Here's the physical description:

    It's about 1/4" in diameter and 1/8" thick. The 2 leads are about
    1/4" apart. The color is black with white charactors, which I next
    describe. It has a triangle laying on it's base (ie, pointing up).
    The corners of the triangle appear to have some detail, perhaps
    looking like arrowheads. I suspect it's the manufacturers logo which
    I think I've seen before, but I don't know which manufacturer. Below
    the triangle are the charactors "K271" and below that "99".
     
  14. j

    j Guest

    Note: I'm trying to cross-post this to sci.electronics.repair, hope
    it works. If not, I'll try to post the info that's there, over to
    here.

    Here's the physical description:

    It's about 1/4" in diameter and 1/8" thick. The 2 leads are about
    1/4" apart. The color is black with white charactors, which I next
    describe. It has a triangle laying on it's base (ie, pointing up).
    The corners of the triangle appear to have some detail, perhaps
    looking like arrowheads. I suspect it's the manufacturers logo which
    I think I've seen before, but I don't know which manufacturer. Below
    the triangle are the charactors "K271" and below that "99".
     
  15. j

    j Guest

  16. Phil Allison

    Phil Allison Guest

    "j" <

    ** That is the Matsushita logo:

    http://members.chello.nl/~h.dijkstra19/image/matsushita logo.jpeg

    aka National / Panasonic



    ** Its a 270 volt MOV.

    Similar to these, but the older K series.

    http://industrial.panasonic.com/www-data/pdf/AWA0000/AWA0000CE2.pdf



    ...... Phil
     
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