Replacing an ethernet cable jack
A week ago my 4 year-old daughter bounced on the bed and knocked off my laptop. The laptop was fine, but the ethernet cable had some minor damage. The plastic tab on the RJ-45 plug, which holds it in the computer socket, snapped off. At first, this didn’t seem like a big deal. The cable still worked well. But at random moments it would fall out of the socket and I would lose my internet connection. This got annoying pretty quickly.
Learning how to make an ethernet cable has been on my list for a while. And I didn’t want to lose this particular cable, which is exceptionally long and lets me move the laptop anywhere in the room. (We do have wireless throughout the house, but I like that high-speed.) So I figured I would do a quick and dirty repair and just replace the connector. I picked up 20 of them at Best Buy for $6.99. I didn’t get any other specialized tools, normally an RJ-45 crimping tool is recommended, but I figured my tabletop vise would do as well.
There are many sites that show you how to make an ethernet cable, so I won’t repeat it here. When I made a ribbon cable I was impressed with the elegance and fool-proof nature of the connection. That was not the case here. It is necessary to line up 8 colored wires in the proper order and insert them into the slots of the connector. It is extremely easy for one wire to slide over another as you do this, forcing them into the wrong slots. I crimped my first connector before seeing this error, so I had to cut it off and start all over. Fully straightening each wire and trimming them to exactly the same length is important.
All in all I had to re-insert the wires dozens of times to get them in the right order. I didn’t time it, but total replacement time was 45 minutes to an hour. That is much longer than it should take, and I’m sure a pro would do much better. Compared to the ease of connecting a ribbon cable, though, I was disappointed. It’s amazing that ethernet cables work as often as they do.
There were a few subtleties I learned that were not obvious, so here they are:
- There are two wiring conventions (at least) for ethernet cables. It doesn’t matter which one you use, at least for a straight cable, as long as you are consistent. But if you are only replacing one connector, you will need to use the same convention as on the other end. In my case, it was T568B.
- The wiring diagrams assume you are looking at the connector with the locking tab underneath.
- A short distance into the cable, I discovered a plastic insert running the length of it, dividing the cable into 4 sections. It was too big to fit in the connector, forcing me to strip more of the outer insulation than standard in order to cut it down.
Good news, the cable works. I don’t think I will go into mass production anytime soon though — happy to pay other people to make these for me.
It’s almost always better in the long run to stick to machine-crimped Ethernet patch cables. It’s very hard to get a good crimp on stranded wire, even with the right crimp tool, and the time and aggravation lost to borderline cables is not worth it. You will also see people use solid wire to make their own patch cables, but solid wire is intended for permanent installation inside a wall – it will eventually break. Even a long patch cable is only a couple of dollars from Monoprice or another source for Chinese factory-made cables.