How to find polarity of a power supply that's lacking the customary markings

Posted by Nosredna on Super User See other posts from Super User or by Nosredna
Published on 2009-07-15T18:09:34Z Indexed on 2010/04/11 4:33 UTC
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power-supply

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polarity

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electricity

If I have a power supply (not a computer power supply, just a battery-replacing wall wart) and it doesn't have the usual polarity marking, how to I know if the tip is positive or negative?

Update: I couldn't find my multimeter. I did find a model number on the power supply and typed it into Google. Some guy selling a bunch of power supplies on eBay had checked it and found that it was tip positive, which is what I needed!

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