How to Repair a Bad Power Plug
It’s such a common occurrence that you’ve probably experienced it firsthand. The power adapter plug that goes into your notebook computer starts to become flaky. You have to wiggle the cord, twist it into a certain position or put some tension on the cord by folding it under the computer in order to get it to work. Power adapters can cost hundreds of dollars to replace, but they can often be repaired for free if you already have the necessary materials.
The same thing can happen to the plug on any kind of power adapter, but it happens most frequently with notebook computer power supplies, especially ones with coaxial cords. This is because people carry notebook computers and their power adapters with them all the time, and the constant wrapping and unwrapping of the cord, combined with the manipulation of the plug, can cause it to fail. It’s not the plug that goes bad on a power adapter, but the cord itself, or more specifically, the connections between the cord and the plug fail. This happens often to headphones, too, but these are usually impossible to fix because of the kind of wire used; fortunately they’re inexpensive to replace.
The photo above shows a typical coaxial power plug. At the factory, the wires coming from the cord are soldered and/or crimped to contacts on the metal portion of the plug, and then a vinyl jacket is molded around the assembly to provide strength and to form a grip. Too much flexing of the cord causes the connections between the plug and cord to fail inside the molded jacket.
If you have a power adapter that works intermittently, especially when you wiggle the plug, it’s more than likely that the wires have disconnected from the plug itself or that they’re shorting out (touching each other). Either way, the repair is the same. And by the way, you should stop wiggling the plug and either fix it or replace the power adapter because wiggling the plug can damage the socket in your notebook computer, and repairing that is a complicated and risky process.
It’s always best if you can confirm where the problem is before beginning a repair. If you have a volt meter, it’s a simple matter to check the output voltage of the plug and see if it fluctuates as you wiggle the cord. If the voltage doesn’t fluctuate, the socket in your notebook computer could be damaged and, again, repairing that is complicated and risky.
Sometimes the cord can fail right where it exits the power brick. If wiggling the cord there causes problems, there’s no need to repair the plug. But your only option might be to replace the power adapter because you would have to open up the adapter to make this repair, and they’re not designed to be opened or serviced in any way. If you’re ambitious enough, you might be able to cut open the power adapter, cut off the bad part of the cord and solder it back into place. Even though you could do more harm than good, if the power adapter isn’t working, you’ve got nothing to lose.
If you’ve determined that the problem is with the plug, you have to either replace the plug or repair the electrical connections to it. If you can find an exact replacement for the plug, say at Radio Shack™, you might be better off simply clipping the old one and soldering on a new one. Just be sure to connect positive and negative correctly. Positive is usually the inner sleeve and negative is the outer part of the plug. Before you do anything, though, make sure the power adapter is not plugged into an AC outlet.
To repair the old plug, you have to start by cutting off the jacket surrounding the contact points, as shown above. You can simply slice the jacket down its side with a razor blade and peel it off or cut the plug off and wiggle the metal part out of the vinyl jacket. Either way, what’s important is that you not damage the metal part of the plug, which will be reused. What’s even more important is that you don’t cut yourself when using a razor. Be careful! You’ve been warned.
Now you can cut the excess wire off the plug and cut the messy end off the cord. The plug used in these photos had the inner wire crimped into place—the bare wire is slipped inside the inner sleeve, which is then crimped (crushed) to hold the wire in place. To get the wire out, it’s best to “un-crimp” the sleeve by squeezing it back into a circle with needle-nose pliers. Just don’t damage the sleeve. If the center wire is soldered in place you have to heat it up with a soldering iron and pull it out once the old solder is melted. Be careful what you touch when using a soldering iron. Things get hot. Don’t burn yourself. Use pliers or tweezers when needed. The outer negative connection is always soldered and you can simply heat up the solder and pull off the wire, or use solder wick, which keeps things neater.
Solder wick is flat braided copper used to remove solder. You simply place it over the old solder and press down on it with a hot soldering iron. The wick will soak up the solder when it melts. Then you cut off the used portion of the wick and throw it away. Solder wick, along with solder, soldering irons and other tools you might need may be purchased at Radio Shack™, hardware stores, and other places that carry electronic parts and repair items.
When you’re finished removing the old solder and wire from the plug it should look something like what you see above.
It’s time to prepare the ends of the cord, as shown above. Cut the center wire down to roughly 1/2 inch and strip off about 1/8 inch of the insulator. Twist the outer wire together as shown and cut its length down to about one inch. The length of the wires is critical. The center wire should fit into the plug’s center sleeve and the outer wire should reach the outer part of the plug where the old length of wire was soldered to it.
Next, slip the bare end of the center wire into the inner sleeve and crimp the sleeve to hold it in place. You can use the wire-cutting jaws of needle-nose pliers to do the crimping, but don’t squeeze so hard that you cut right through it. You can solder the center wire instead, but don’t let it get too hot, as the plastic parts of the plug can melt, rendering it useless. Now slip a short length of heat-shrink tubing over the exposed outer wire and shrink it in place with a lighter, leaving at least 1/8 inch of the wire bare. This will prevent the outer wire from touching the inner conductor. You can use electrical tape instead of heat-shrink tubing, but the tubing is much more efficient. It doesn’t take much heat to shrink the tubing; try not to burn it.
Now it’s time to solder the outer wire to the outer part of the plug, as shown above. You might need three hands, a small vise or clamp to do this. Work neatly and don’t use too much solder, which could create a short between the inner and outer parts of the plug.
All that’s left to do is to slip a larger piece of heat-shrink tubing over the plug and its contacts and shrink it in place as shown above. The tubing should cover part of the insulation on the cord and the soldered connection on the outer part of the plug.
The tubing stiffens as it shrinks, providing some strength to the assembly. Even so, it’s a good idea to shrink another layer or two of tubing over the assembly as shown above to provide even greater strength to the repair. If you have a volt meter, you can use it to verify that the power adapter is now working properly. It should plug right into your computer and work like new.
Things You’ll Need