Ever have an Airport Express (AE) that will not power up anymore? Most likely it is from a broken power supply unit. The cause is usually from a bad 3.3v regulator and/or bad capacitors. This guide will show you how to bypass Airport Express PSU and power it with USB power. This will great if you want to use an 5v USB A/C adapter, power it off your computer, or use any other USB power source.
Here is a list of suggested tools and materials you might need:
Soldering Iron, Solder
USB Compact Flash card reader, $2 online (slightly smaller than the AE so it fits inside)
3 wires (2-3inch in length), one for ground, one for 5v and one for 3.3v.
Update: I changed the blue tape to white tape on the reassembly of the housing.
Step 1: How to Open the Airport Express Case
Use the hand saw and cut along the case seam of the Airport Express. The seam is where the two pieces of the case is joined together. The depth you need to saw is 1/8 of an inch. You should stop right when the plastic breaks through and you can see the insides. Go slowly as you do not want to damage anything inside.
Step 2: Disconnect the Power Cable
Once open, disconnect the power cable from the power supply. There should be three ground wires (black), one 5v wire (red), and two 3.3v wires (orange).
Step 3: Test the CF Memory Card Reader
Use your multimeter and find the locations of the ground, 5v and 3.3v on your CF Memory Card reader. I am using the CF memory card reader for two reasons. One, it provides me with an existing USB port. And, two, a CF card reader provides a 3.3v output. AE runs on both 5v and 3.3v. You can create your own 3.3v stepdown if you want.
You can use your multimeter and test your power supply too. A word of warning, there is a risk of electric shock if you do decide to tinker with your broken AE power supply.