Detecting a break in audio cables

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.

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.

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

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

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

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

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