DVR Small Hardware Problem

Discussion in 'General Electronics Chat' started by hazim, May 2, 2014.

  1. hazim

    Thread Starter Active Member

    Jan 3, 2008
    419
    13
    Dear,

    I have a problem in a CCTV system when some electric shock or electromagnetic effect had damaged 3 cameras and 3 inputs of a DVR. The three cameras are connected to the DVR via UTP cable with video baluns.

    The cameras have several burnt components in the board so I will replace the boards.
    The DVR have the 3 port's 75 Ohm resistors burnt out but also another paralleled component with these 3 resistors named as S as the resistor is named as R and capacitor as C...etc... so what is the "S" component? some suppression component? with what should I replace it?

    The attached image clarify the components.

    Regards,
    Hazim

    [​IMG]
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,998
    745
    easiest way is to measure the other capacitors to compare values, then replace the faulty one like for like.
     
  3. hazim

    Thread Starter Active Member

    Jan 3, 2008
    419
    13
    But how you know that "S" is a capacitor?? there is a "C" on the board referring to capacitor, but this should be a different component other than capacitor. Also, usually smd capacitors color is brown while these S's are black or dark grey. I think they are something like varistors.
     
  4. bertus

    Administrator

    Apr 5, 2008
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  5. #12

    Expert

    Nov 30, 2010
    16,313
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    You are in a better position to measure them than we are.
    Give it a try and find out if they are capacitors.
     
  6. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    They will be bidirectional TVS components.

    That's a guess, based on seeing similar 3-part setups in other appliances, although I have never seen the "S" designator on the PCB (or don't remember seeing it).

    "S" for "Supressor" might be what they were thinking.
     
    hazim likes this.
  7. hazim

    Thread Starter Active Member

    Jan 3, 2008
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    Yes it seems some supressor component, as I found Z-shape symbol under it. Anyway, this is a protection item against high voltage such as varistor as I expect.

    I replaced the 75 Ohm resistors but the DVR defected inputs didn't worked. There would be damaged IC's. Better to replace the DVR.
     
  8. ian field

    Distinguished Member

    Oct 27, 2012
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    S could be for sidac - apparently a diac-zilla type component.
     
    THE_RB likes this.
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