Need help wiring cat5 cable with odd color pairing
January 9, 2015 10:39 AM   Subscribe

How do i wire this rj45 cat5 cable which has an odd color pairing inside?

I have a long RJ45/cat5 cable that I wanted to shorten. I cut a length of it off with the connector figuring it would have the standard color pairings of other cat5 cable. When I opened it up however, there are 8 wires (as expected) organized in 4 separately shielded twisted pairs. The pairs are: Brown-White, Blue-White, Light Orange-White and Green-Orange. This stumped me. Normally I would just look at the way the other connector was paired but it the original connector is tinted a dark red which makes it impossible to see the colors. I assumed then that each white wire is the striped version of the color its paired with. So Brown-White = Brown + Striped white/brown. But the orange one is throwing me off completely. I tried assuming that it was the striped green/white since it was paired with green but that didn't work.

Anyone ever seen this kind of color pairing before?
posted by postergeist to Computers & Internet (15 answers total)
 
I'd try dremeling open the plastic on the connector you cut off and see how it's organized
posted by colin_l at 10:51 AM on January 9, 2015 [1 favorite]


Do you have a multimeter? If so, set it for resistance or continuity test, and strip a little bit of the ends of each wire. You should be able to tell which wire connects to which pin by checking for continuity between the stripped end of one wire and each pin in turn, until you find the right one.

For a sanity check, the pairs should be arranged as:

Pair 1
Pair 1
Pair 2
Pair 3
Pair 3
Pair 2
Pair 4
Pair 4

(Assuming this is a straight-through cable for Ethernet).
posted by FishBike at 10:51 AM on January 9, 2015


Best answer: (And of course if you don't have a meter, you could just cut the other end off and re-terminate both ends, as long as you arrange the pairs as above.)
posted by FishBike at 10:53 AM on January 9, 2015 [5 favorites]


Response by poster: @FishBike: thanks for the tip. So if I understand correctly, as long as both terminals are wired in the same order, it will work?
posted by postergeist at 11:11 AM on January 9, 2015 [1 favorite]


Yes, as long as both terminals are wired as FishBike says, it's fine. And, no, the pairings aren't all solid w/their respective striped. We usually do Brown/BrownWhite, Green/BlueWhite, Blue/GreenWhite, Orange/OrangeWhite.
posted by The Great Big Mulp at 11:28 AM on January 9, 2015


Here is a picture (use straight through)
posted by H21 at 11:34 AM on January 9, 2015


So if I understand correctly, as long as both terminals are wired in the same order, it will work?

Provided that they are paired correctly (like fishbike says), yes. If the other end is wired correctly, you can just copy it. If the other end is wired incorrectly, you will have to cut it off and redo it also.

An orange/green pair is pretty weird. I also haven't seen a cable where the individual pairs were shielded; the shielded cables I've seen have had one sheath around all eight conductors, but it's been a while since I've monkeyed with this stuff, so maybe that's a thing people are doing now.
posted by aubilenon at 11:42 AM on January 9, 2015


Response by poster: Ok got it. good advice. Thanks all.
posted by postergeist at 11:46 AM on January 9, 2015


Yes. Unless you want a crossover cable, as long as both are wired the same, it *should* work. Unless there's some other funky confounding variable.
posted by colin_l at 11:53 AM on January 9, 2015


Response by poster: Crimpin' aint easy
posted by postergeist at 12:01 PM on January 9, 2015 [4 favorites]


So if I understand correctly, as long as both terminals are wired in the same order, it will work?

Not just the same order, but with the pairs kept together as in the diagram I typed, e.g. one pair on the left-most pins, another pair on the right-most pins, and the remaining two pairs "one inside the other" on the middle 4 pins.

This is because with these kinds of cable, any signal put onto it is put on both wires in a pair in a balanced fashion (e.g. + on one wire and - on the other) and they must remain tightly twisted together for their entire length or the signal doesn't make it to the other end. This kind of thing is often the cause behind a cable that tests fine with a multimeter or cheap cable tester, but fails to work with actual data signals.
posted by FishBike at 12:02 PM on January 9, 2015


Crimpin' aint easy

I find the hardest part is usually getting all 8 wires to lay flat and stay tightly together to shove them into the connector properly, because they keep wanting to spring back into their original position.

The trick to it is leave them all a bit too long initially, get them lined up the way you need and hold them between your thumb and forefinger of both hands. Then wiggle your hands slightly in opposite directions. Bending the wires a little bit back and forth (like the bristles on a toothbrush) relieves the existing stress in them and then they'll sit however you were holding them when you did that. (This is kind of hard to describe in text.)

After that you can just cut them to the right length and they should slide right into the connector on the first try.
posted by FishBike at 12:08 PM on January 9, 2015 [1 favorite]


Response by poster: Like this ?
posted by postergeist at 12:17 PM on January 9, 2015


Response by poster: Fortunately after many years of practice, getting the wires to line up isn't a problem for me anymore. The trick is like you say, leave them long, then line them up. But after that the important bit I find is how you cut them. Sometimes the wires are so tightly twisted up inside the shielding that I find cutting them so that the end wires are the longest going successively shorter towards the middle works well. If they line up nicely without having to jostle them into position on the other hand then a nice straight line cut across them to make sure they are all perfectly even just before you slide the terminal on makes the job much easier.
posted by postergeist at 12:22 PM on January 9, 2015 [1 favorite]


Response by poster: nevermind that image i posted. I misunderstood. Anyway, i got it working! thanks everyone. Tip for those of you who follow this thread later.. don't scrimp on the crimp!! I bought a cheap piece of shit crimper and it shows. I ended up having to push each pin into place individually with the end of a jewlers scredriver and after that (and correct wiring of course) it worked!
posted by postergeist at 1:03 PM on January 9, 2015 [1 favorite]


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