I mean, the simplest answer is to lay a new cable, and that is definitely what I am going to do - that’s not my question.
But this is a long run, and it would be neat if I could salvage some of that cable. How can I discover where the cable is damaged?
One stupid solution would be to halve the cable and crimp each end, and then test each new cable. Repeat iteratively. I would end up with a few broken cables and a bunch of tested cables, but they might be short.
How do the pro’s do this? (Short of throwing the whole thing away!)
Higher end cable testers can show you where the break is, but it will be far more expensive that a new cable.
I had an AMD Phenom-II era motherboard that claimed it would be able to do that. OP, you might be able to find an old NIC/mobo that could do this for cheap.
My TP link switch can detect faults and cable length. I’m not sure it can do both together but it’s possible. Worth checking if you have a switch with those features
Wire tracker maybe? You might want a higher quality version than that particular one if the cable run is long, one of the reviews suggest that the distance is limited.
This one here does time domain reflectiometry which will tell you exactly where the break is:
https://www.amazon.com/Ethernet-NF-8209-Distance-Location-Measurement/dp/B08M3SRB2Q/
How do you know the cable is damaged? If you have a toner you can hook the generator to the damaged pair and listen along the length of the cable to where the tone changes. It’s not as fool-proof as a tester, but much cheaper.
You can only do 100M runs max anyways, just replace the whole thing? 100M of CAT6 is pretty cheap if you already have a box for it.
Or is this an academic question?
Actual, not academic. And I agree that a new cable is cheap, which is what I will do. My question is about avoiding throwing a mostly good cable in the trash.
If you just want some spare cable. I’d make 5x 20M pieces. The one that doesn’t work becomes 2x 10M. That bad one becomes 2x 5M … As far down as you like.
Isn’t that almost what they suggested except starting at a different size and doing a binary search basically? You’re just starting the binary search after the first step of cutting into 5 lengths instead of 2.
Can’t you just use a cheap non-contact voltage tester to find where the cable is damaged? Just run the tester through the cable until it suddenly stop detecting any AC voltage, which is probably where the cable is broken. But if you’re talking about ethernet cable, then I have no idea.
I just learned about these things today when researching for a device to test that there’s no voltage present before installing a ceiling light. Such a great innovation since it works even through insulation, so no risk of getting shocked.
The easiest thing to do would just be to pull it out and look at it. The break might be obvious.
You only need 2 pairs for 100base-t, try forcing a lower negotiation, see if the pairs you need work? Maybe unbundle the other set of pairs and try them?
That sounds triggered.
