Detecting a break in audio cables

Discussion in 'Electronic Repair' started by M.Joshi, Aug 28, 2006.

  1. M.Joshi

    M.Joshi Guest

    Hello,

    Is there a way to detect where a break has occurred in an audi
    interconnect cable?

    I tried conecting one end to a 1KHz signal generator and attempting t
    detect the signal down the cable with a sensitive amplifier & speake
    however, it seems that the signal is being induced onto the screen a
    well since it can be detected along the length of the cable


    --
    M.Joshi
     
    M.Joshi, Aug 28, 2006
    #1
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  2. M.Joshi

    Bob Guest

    M.Joshi wrote:
    > Hello,
    >
    > Is there a way to detect where a break has occurred in an audio
    > interconnect cable?
    >
    > I tried conecting one end to a 1KHz signal generator and attempting to
    > detect the signal down the cable with a sensitive amplifier & speaker
    > however, it seems that the signal is being induced onto the screen as
    > well since it can be detected along the length of the cable?
    >
    >
    >
    >

    I have an almost perfect method for detecting the exact point of a
    break. You simply measure the capacitance across each end and perform a
    simple ratio calculation.

    Generally the break is at or near one end. So you might measure 150 pF
    across one connector and 3 pF across the other. Obviously the break is
    at the second one.

    On the other hand, if the two capacitance are nearly equal, the break is
    near the middle. To get the most accurate point, subtract about 2 pF
    from each reading to eliminate the connector from the equation and then
    the ratio of the readings is the location of the break.
     
    Bob, Aug 28, 2006
    #2
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  3. M.Joshi

    Bob Guest

    Another method

    You can also use TDR, or Time Domain Reflectometry. Send a pulse into
    one end and see how long it takes for the reflection to return. This
    requires more sophisticated equipment of course.
     
    Bob, Aug 28, 2006
    #3
  4. M.Joshi

    M.Joshi Guest

    Bob Wrote:
    > M.Joshi wrote:-
    > Hello,
    >
    > Is there a way to detect where a break has occurred in an audio
    > interconnect cable?
    >
    > I tried conecting one end to a 1KHz signal generator and attemptin
    > to
    > detect the signal down the cable with a sensitive amplifier & speaker
    > however, it seems that the signal is being induced onto the screen as
    > well since it can be detected along the length of the cable?
    >
    >
    >
    > -
    > I have an almost perfect method for detecting the exact point of a
    > break. You simply measure the capacitance across each end and perfor
    > a
    > simple ratio calculation.
    >
    > Generally the break is at or near one end. So you might measure 150 p
    >
    > across one connector and 3 pF across the other. Obviously the break i
    >
    > at the second one.
    >
    > On the other hand, if the two capacitance are nearly equal, the brea
    > is
    > near the middle. To get the most accurate point, subtract about 2 pF
    > from each reading to eliminate the connector from the equation and the
    >
    > the ratio of the readings is the location of the break.



    Are there any other methods as I currently do not have a capacitanc
    meter or a multimeter with a capacitance range


    --
    M.Joshi
     
    M.Joshi, Aug 29, 2006
    #4
  5. M.Joshi

    N Cook Guest

    M.Joshi <> wrote in message
    news:...
    >
    > Bob Wrote:
    > > M.Joshi wrote:-
    > > Hello,
    > >
    > > Is there a way to detect where a break has occurred in an audio
    > > interconnect cable?
    > >
    > > I tried conecting one end to a 1KHz signal generator and attempting
    > > to
    > > detect the signal down the cable with a sensitive amplifier & speaker
    > > however, it seems that the signal is being induced onto the screen as
    > > well since it can be detected along the length of the cable?
    > >
    > >
    > >
    > > -
    > > I have an almost perfect method for detecting the exact point of a
    > > break. You simply measure the capacitance across each end and perform
    > > a
    > > simple ratio calculation.
    > >
    > > Generally the break is at or near one end. So you might measure 150 pF
    > >
    > > across one connector and 3 pF across the other. Obviously the break is
    > >
    > > at the second one.
    > >
    > > On the other hand, if the two capacitance are nearly equal, the break
    > > is
    > > near the middle. To get the most accurate point, subtract about 2 pF
    > > from each reading to eliminate the connector from the equation and then
    > >
    > > the ratio of the readings is the location of the break.

    >
    >
    > Are there any other methods as I currently do not have a capacitance
    > meter or a multimeter with a capacitance range?
    >
    >
    >
    >
    > --
    > M.Joshi


    Breaks in cables including co-ax cable.
    Use a needle point probe to pierce the outer (and braiding of co-ax)
    to pick up the core and use a continuity checker. Breaks are often near the
    end at the
    connector ;so can cut back perhaps a few inches and reuse the rest of the
    cable .
    Waggle the probe ( needle in a bit of dowel) around to move the screening
    out of the way a bit to engage only the core.

    other hints and tips on 2 files on URL below

    --
    Diverse Devices, Southampton, England
    electronic hints and repair briefs , schematics/manuals list on
    http://home.graffiti.net/diverse:graffiti.net/
     
    N Cook, Aug 29, 2006
    #5
  6. M.Joshi

    Guest

    M.Joshi wrote:
    > Bob Wrote:
    > > M.Joshi wrote:-


    > > Hello,
    > >
    > > Is there a way to detect where a break has occurred in an audio
    > > interconnect cable?
    > >
    > > I tried conecting one end to a 1KHz signal generator and attempting
    > > to
    > > detect the signal down the cable with a sensitive amplifier & speaker
    > > however, it seems that the signal is being induced onto the screen as
    > > well since it can be detected along the length of the cable?


    > > I have an almost perfect method for detecting the exact point of a
    > > break. You simply measure the capacitance across each end and perform
    > > a
    > > simple ratio calculation.
    > >
    > > Generally the break is at or near one end. So you might measure 150 pF
    > >
    > > across one connector and 3 pF across the other. Obviously the break is
    > >
    > > at the second one.
    > >
    > > On the other hand, if the two capacitance are nearly equal, the break
    > > is
    > > near the middle. To get the most accurate point, subtract about 2 pF
    > > from each reading to eliminate the connector from the equation and then
    > >
    > > the ratio of the readings is the location of the break.


    > Are there any other methods as I currently do not have a capacitance
    > meter or a multimeter with a capacitance range?


    Make an audio oscillator, using the cable as the capacitance in the
    oscillator. Now you know which end gives high and which end low cap.
    The break is normally at one end, and will be at the end that gives low
    cap reading.

    If you got no equipment at all, just cut 6" off each end of cable and
    refix the plugs, this will fix it almost every time.


    NT
     
    , Aug 29, 2006
    #6
  7. Re: Another method

    Bob wrote:

    > You can also use TDR, or Time Domain Reflectometry. Send a pulse into
    > one end and see how long it takes for the reflection to return. This
    > requires more sophisticated equipment of course.


    That's what I would do too....but I have access to $50k network
    analyzers with the $10k Time Domain option. Using this method, you could
    track down any break to within an inch or so....even closer if using a
    good quality coax cable. Somehow, I sincerely doubt he can afford this.
     
    Caesar Valenti, Aug 30, 2006
    #7
  8. M.Joshi

    Guest

    Re: Another method

    Caesar Valenti wrote:
    > Bob wrote:


    > > You can also use TDR, or Time Domain Reflectometry. Send a pulse into
    > > one end and see how long it takes for the reflection to return. This
    > > requires more sophisticated equipment of course.


    > That's what I would do too....but I have access to $50k network
    > analyzers with the $10k Time Domain option. Using this method, you could
    > track down any break to within an inch or so....even closer if using a
    > good quality coax cable. Somehow, I sincerely doubt he can afford this.


    Its also a piddlingly low return use of high price kit. One could make
    equipment to pinpoint the break just as well for 1/100th the price
    using capacitance. Use 2 oscillators to measure capacitance at each
    end, compare the figures to work out how far along the cable the break
    is, and indicate the result using a moving coil meter. Mounted above it
    is a board with arcs on, lay your cable on that on one of the drawn
    arcs and the needle points to the break.

    Of course there is no real need for either setup, as breaks are
    normally one end or t'other, and the times where this isnt so are few
    enough not to be worth investing in any specialist kit for.


    NT
     
    , Aug 30, 2006
    #8
  9. M.Joshi

    M.Joshi Guest

    Wrote:
    > Caesar Valenti wrote:-
    > Bob wrote:-
    > --
    > You can also use TDR, or Time Domain Reflectometry. Send a puls
    > into
    > one end and see how long it takes for the reflection to return.
    > This
    > requires more sophisticated equipment of course.--
    > -
    > That's what I would do too....but I have access to $50k network
    > analyzers with the $10k Time Domain option. Using this method, yo
    > could
    > track down any break to within an inch or so....even closer if usin
    > a
    > good quality coax cable. Somehow, I sincerely doubt he can affor
    > this.-
    >
    > Its also a piddlingly low return use of high price kit. One could make
    > equipment to pinpoint the break just as well for 1/100th the price
    > using capacitance. Use 2 oscillators to measure capacitance at each
    > end, compare the figures to work out how far along the cable the break
    > is, and indicate the result using a moving coil meter. Mounted abov
    > it
    > is a board with arcs on, lay your cable on that on one of the drawn
    > arcs and the needle points to the break.
    >
    > Of course there is no real need for either setup, as breaks are
    > normally one end or t'other, and the times where this isnt so are few
    > enough not to be worth investing in any specialist kit for.
    >
    >
    > NT



    Thanks for the idea about using a signal generator and substituting th
    capacitor as the wire - i'll give that a go. What's strange is tha
    both the left and right channels are not working which led me t
    believe that the 3.5mm stereo jack end must be faulty. So, I cut off
    few inches of the lead from that end however, the break is stil
    present


    --
    M.Joshi
     
    M.Joshi, Sep 3, 2006
    #9
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