A friend of mine had a power adapter for her laptop that was slowly failing. Eventually, it wouldn't power her laptop anymore so I agreed to take a look at it.
Apple created the MagSafe connector to prevent people from knocking their laptops on the floor if they accidentally tripped over the cord. It is a very sturdy little connector, but in this case, the wires had gotten loose inside the ferule end of the connector.
Since the wires were loose inside the connector, I decided to make things a little worse before I made them better. I pulled the wires out to get a better look at what I was working with. The wire inside is just a 2 wire coaxial cable.
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Step 1: Disassembly
The connector has an aluminum jacket around it that I have been calling a ferule. I clamped the ferule in a vice and used a Dremel with a cut-off wheel to cut a slot in the top and back of the ferule. I had to go very slow and be very careful that I didn't cut too deep. I used a couple pairs of needle-nose pliers to pry the loose ends of the ferule apart.
Step 2: Reassembly
I found the pinouts for the power connector on the end on pinouts.ru. I used my multimeter's continuity tester to find which side of the internal connector was which. Then I used the voltage meter to find which wire in the cable was positive and which was negative.
After I striped the outer jacket off the power wire, I saw that this wire is made like coax cable. It has a mesh of wire outside another fully-insulated wire. I pulled the wire mesh out and twisted it up to make a regular wire. I decided to heat-shrink some insulation on the bare conductor to avoid any shorts on the aluminum ferule when I put everything back together.
I tinned the wires to make it easier to solder them to the end of the connector. With the connector in a helping hand clamp, I soldered the wires to the end of the connector. I then plugged the power supply into the wall and used the voltage meter again to test the voltage. According to pinouts.ru, the voltage should show 6.86 VDC under no load, which is what I got when I touched the leads to one inner and one outer contact on the connector.
I put a little piece of electrical tape over the exposed electronics on the back of the connector and put the ferule back in place around everything. I squeezed the ferule back around everything with a set of pliers, but there was still a gap at the top and the back where I had cut away the metal.
Step 3: Clean-up
Once everything was back together and tested, I needed to patch up the missing parts of the ferule casing. I like to use epoxy putty when I need to rebuild material and I need the fix to be really strong. Epoxy putty is just like epoxy, but it comes in a roll of clay. There are 2 different colors in the roll, one on the outside, one on the inside and you mix them together in your hands to start the chemical reaction.
I used this white putty that is a little softer than the black, plumber's putty that I usually use. I figured, since it's for a Mac it should be white. Unfortunately, there was no easy way to leave the LEDs exposed.
I gave the repaired adapter back to my friend, and everything is working perfectly!
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