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:

Power Adapter

This is the multimeter I'm using:


Thank you


1 Answer 1


This adapter is just a fused transformer in a box. It gives an isolated ac voltage output. There is no polarity in such a system. One wire will have a sinusoidally varying voltage around the other, sometimes positive, sometimes negative. Therefore you may connect the wires either way.

If you want a dc output, with one wire having a constantly positive voltage above the other, you bought the wrong item.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.