I am shopping for an AC/DC power adapter for an external hard drive, and I've noticed that the power supply required for the couple of the external hard drives I looked at is always with positive polarity. This made me wonder: Do all external hard drives require a power supply with positive polarity? In other words, if I buy AC/DC power adapter for an external hard drive, should its output always have positive polarity, or does that depend on the external hard drive?
