I purchased a power adapter so that I could put a different plug on it, but when I cut the wire and stripped it, it didn't have a colored jacket on it. The brick does not have a diagram on it, so I have no way of knowing which is positive, and which is negative.
I have a multimeter, and set it to AC Voltage, and touched the red lead to one wire, and the black to the other. it was a positive voltage reading. I switched the leads and wires, and I got a postive voltage again. This is the power adapter I used:
This is the multimeter I'm using: