Capacitor help please

Discussion in 'General Electronics Chat' started by daveyhouse, Feb 3, 2007.

  1. daveyhouse

    Thread Starter New Member

    Feb 3, 2007
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  2. daveyhouse

    Thread Starter New Member

    Feb 3, 2007
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    This is what I can read off of it

    MED
    C471
    R3.2-5.2? <cannot make out that symbol
    125V

    This item connected a coax lead to the tuner on a tv
     
  3. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    No clue about "MED" save that the M in three leter capacitor codes often means "metallic."

    "C471" = "470 picofarads, plus or minus one quarter picofarad."

    "R3" by itslef would mean "made in March of 2003." I don't know it such is the case here.

    "125V" means "rated for a maximum of 125volts." Since AC is not specified, assume 125 volts DC (max 88 volts AC).
     
  4. daveyhouse

    Thread Starter New Member

    Feb 3, 2007
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    thank you for the response thingmaker3.

    I went to rat shack picked up a set this morning she said it "should" work
    472K
    500WVDC MAX
    0.0047uF
    http://www.radioshack.com/product/index.jsp?productId=2102418&cp

    Okay we can see channels now, but they are snowy. So I guess this item will not work.
    I see that they also have another @50v would I be better trying one of these? http://www.radioshack.com/product/index.jsp?productId=2062364&cp=2032058.2032230.2032267&allCount=100&fbn=Type%2FCeramic+Disc+Capacitors&f=PAD%2FProduct+Type%2FCeramic+Disc+Capacitors&fbc=1&parentPage=family

    Thanks Again,
    Dave
     
  5. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Hi,

    What led you to suspect/replace that capacitor? Usually, only some disaster with lightning will cause one of them to fail, and by then, the rest of the tuner is toast.

    One of the semiconductors is a more likely cause of the failure than a passive component.
     
  6. daveyhouse

    Thread Starter New Member

    Feb 3, 2007
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    Okay here is the scenario.
    This one of my childrens tv sets. They are always moving things around. I guess they over tightened the cable coax and twisted the thing right out of its base. So I took it apart to solder back together. I got the fitting back on securely but capacitor legs were also torn off. No electrical damage, just physical.

    Update: I think the reason for the snowy picture is due to a resistor that connects to the coax shielding. When I tested with multi-meter, I did not get any reading. So I guess that means it is totally open.

    The colors on this were grey, red, green, silver. = 8.2 Mohms yes? (web calculator) (I love google)
    What is the M for? million?

    Anyway when I inserted the coax lead wire without connecting the shield I have snowy picture, I then connect the shield and nothing changes. That is what made me follow the shield path.

    Thanks again, your forum is awesome.
    Dave
     
  7. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
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    This is why I never go to Rat Shack! 470pF=0.00047uF, not 0.0047uF. Any source on the planet other than Rat Shack would have a card hanging handy to make conversions. Arrrgh! :mad:

    Sorry. Rant over now... :(
     
  8. daveyhouse

    Thread Starter New Member

    Feb 3, 2007
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    thanks for the help.
    Does anybody have a favorite site that they prefer to order components from?
     
  9. mrmeval

    Distinguished Member

    Jun 30, 2006
    833
    2
    Televisions have very critical AC isolation on any metallic protrusion. In some sets the isolation is provided by a switched mode power supply.

    In a television that has a "hot chassis" where raw AC is rectified, filtered and sent to a linear regulator (or in some cases a type of smps that does no isolation) the AC and DC usually share grounds. Isolation in those televisions is provided by special capacitors and a metal box that has the RF connector on it which then plugs into the tuner. Anything that compromises this isolation can place line voltage on the coax connector. This can electrocute you or your children though it is most likely to short the AC to ground and blow the bridge rectifier and fuse when you attach the coax and plug it in.

    In some sets the box will be a box that has a cable plugged into the tuner with the box mounted on the back of the set. Others the box has no cable and the tuner is close enough to the back for the RF connector to fit through. If the RF connector goes into the back of a large rectangular box you may be ok. ...

    That device may be a capristor

    This is about all I could find to point out what I'm saying.
    http://www.patentstorm.us/patents/5351018-description.html

    http://www.epanorama.net/links/repair.html
    Don't have the TV hooked to anything except the power when you do this.

    I had one of these made up for "quick and dirty" testing a long time ago.
     
  10. daveyhouse

    Thread Starter New Member

    Feb 3, 2007
    6
    0
    mrmeval, thank you for those links. Very informative.

    I guess I am 86'ing this project. I replaced the cap and resistor, found an old local man that had pieces that I needed.

    Snowy picture remains. It is only when it is hooked up to local cable company. If I hook an OTA antenna the picture is clear. Go figure

    Thanks
    Dave
     
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