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I have a wire for a lamp post that’s been hit. It’s buried already. I’m trying to locate the break. I’ve tried for continuity and obviously get nothing. Now when I put a toner on I’m still getting a strong tone on the other end. I’m trusting my meter before the toner but wondering why I’m still getting a tone on the wire.
 

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An oscilloscope would indicate where the break is.
Used one when I was on a cable repair crew in the refineries on the Houston Ship Channel.
Cables were mostly 300 pair strung overhead and had damage primarily from backhoes and cherry pickers that no one reported.
But not everyone has an oscilloscope handy.
 

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You need an underground fault locator. We use an RD7000.

If you don't have access to one, hire someone who does. Also, once you find the bad spot and cut it apart, it's good practice to isolate the wiring at both ends and meg it. It's not uncommon to find other issues.
 

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An oscilloscope would indicate where the break is.
Used one when I was on a cable repair crew in the refineries on the Houston Ship Channel.
Cables were mostly 300 pair strung overhead and had damage primarily from backhoes and cherry pickers that no one reported.
But not everyone has an oscilloscope handy.
How can an oscilloscope find a break ?? :unsure:
 
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I guess it's possible to find the general location without a fault locator but I have never tried it.
If it's a fault and you know the path that the cable is traveling. It could be determined by measuring resistance between two cables.
 

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How can an oscilloscope find a break ?? :unsure:
It will send an oscillating wave through the wires that can be monitored.
A break in a cable, no matter how small, will upset the wave.
Don't remember all the particulars, but it would get us with two to three feet of the bad spot.
 

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It will send an oscillating wave through the wires that can be monitored.
A break in a cable, no matter how small, will upset the wave.
Don't remember all the particulars, but it would get us with two to three feet of the bad spot.
I believe you are thinking of a TDR, a time domain reflectometer.

I picked one up years ago, to do what we are talking about here, but never spent the time to learn how to use it properly. We always ended up just using a fault/wire locator. Which also has the side benefit of locating the wire path, as well as the fault location. A TDR will only tell you the distance to the fault, but it won't locate the wiring path underground for you. So it makes it somewhat worthless for underground fault finding, since you usually need a locator anyways, unless you know the exact wire path already.
 
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