Determining that a cable has a broken conductor is the easy part, but where exactly is the break? In a recent video, [Richard] over at the Learn Electronics Repair channel on YouTube gave two community-suggested methods a shake to track down a break in a proprietary charging cable. The first attempt was to run a mains power detector along the cable to find the spot, but he didn’t have much luck with that.

The second method involved using the capacitance of the wires, or specifically treating two wires in the cable as the electrodes of a capacitor. Since the broken conductor will be shorter, it will have less capacitance, with the ratio theoretically allowing for the location of the break in the wire to be determined.

In the charging cable a single conductor was busted, so its capacitance was compared from both sides of the break and compared to the capacitance of two intact conductors. The capacitance isn’t much, on the order of dozens to hundreds of picofarads, but it’s enough to make an educated guess of where the rough location is.

How To Find Where A Wire In A Cable Is Broke. Which End Of The Broken Cable?
https://www.youtube.com/watch?v=FOzEpJogSFg

I was recently working on an ebikecharger and a I have a broken wire in a cable. It’s easy to find which wire is broken, but wher in the cable is the break? In this video I test two different methods to find the break in the cable.

In the mid-1970s, HP developed a set of three handheld probes; a logic probe (HP 545A), a current pulser (HP 546A), and a current tracer (HP 547A). These were replaced later with the updated HP10525T logic probe and 10526T pulser sold together as the HP 5015T Logic Troubleshooting Kit. As far as I know, the current tracer was not upgraded. The combination of current pulser and current tracer were originally meant to locate shorts or latch-ups in CMOS and HCMOS circuits, circuit board shorts, and so forth.

The original user manual says:

The HP 547A Current Tracer is a hand-held probe which enables the precise localization of low impedance faults in electrical systems. The probe senses the magnetic field generated by a pulsing current internal to the circuit or by current pulses supplied by an external stimulus such as the HP 546A or 10526T Logic Pulsers. Indication of the presence of current pulses is provided by lighting the indicator lamp near the Current Tracer tip. Adjustment of probe sensitivity over a 1 mA to 1A range is provided by the SENSITIVITY control near the indicator.

It occurred to me recently that the current tracer might help map out the path of ESD discharge currents, especially for complex systems with multiple circuit boards, power supplies, and cables.

We were easily able to isolate the path of ESD to just a few of the cables as well as the display board. The lamp brightness indicated the relative amplitude (and dominant path) of injected ESD current pulse.

Current-tracer probes were more prevalent 10 years ago, but occasionally I see them pop up on eBay or other surplus outfits for $50 to $100. This just might be the right tool for those really difficult ESD challenges and I plan to keep this in my troubleshooting kit.

You are also right that
“the receivers are sensitive to the AC voltage field, and simply have a very high impedance amplifier.”

I have even built some circuits like that
https://www.epanorama.net/blog/2013/03/05/cable-tracing-inductive-amplifier/

AC induction is an electromagnetic phenomenon where a changing magnetic field—often from power flow through nearby power lines—can cause an induced current and voltage to be present on conductors that are nearby and not actually connected to any power supply. The strength of the induced current and voltage depends on factors such as the power source distance and current.

Term “induced voltage” can sometimes used to describe voltages caused by both inductive and capacitive coupling between wires
https://www.tdworld.com/overhead-distribution/article/20971744/the-effect-of-transmission-lines-on-railroads
AC electricity causes induction because of the constantly changing character of its magnetic field, as voltage changes repeatedly between positive and negative.