Most power supplies also have a polarity marking on them in close proximity to the input and output ratings information. The one on mine is so small that scanning it made no sense, but here's my quick hand drawing of the thing:
This indicates that for this power supply the center contact is the positive contact and the outside contact is the negative contact.
I have yet to see a laptop (or similar) power supply that isn't AC input and DC output, so the correct polarity is critical.
Edited by britechguy, 12 November 2017 - 10:34 AM.
Brian AKA Bri the Tech Guy (website in my user profile) - Windows 10 Home, 64-Bit, Version 1803, Build 17134
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