# Okay, stupid question time...



## Moon Dog (Oct 3, 2006)

Can anyone tell me which wire is the positive one on one of those little wall wart power adapters?

Is it the one with the white stripe, or the one without?

Yes, I'm too lazy to use my volt/ohm meter!


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## Mentalist (Sep 23, 2007)

Yes, usually the wire with the white stripe is positive.

M


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## Moon Dog (Oct 3, 2006)

Cool, a fellow Omaha haunter comes through!


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## Otaku (Dec 3, 2004)

Careful! I have a 12VDC wart with a dashed white line on one wire, and that side is negative.


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## Moon Dog (Oct 3, 2006)

Otaku said:


> Careful! I have a 12VDC wart with a dashed white line on one wire, and that side is negative.


Hmmm... that's what the adapter I have has as well...

One wire has a dashed white line and the other wire has printing on it...

Is this the case with the one you have Otaku?

Guess I better be safe and break out the old meter tonight to be sure!


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## Otaku (Dec 3, 2004)

Yes, that's what mine has, too. I always check polarity with a meter - once you cut off the adapter, that's the only way to be sure. Sometimes Harbor Freight sells cheapo meters for 5-6 bucks. Slow response, but good for checking polarity, continuity and verifying resistor values.


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## Mentalist (Sep 23, 2007)

Before you go any further, you may wish to verify that you have an AC to DC transformer. While rare, AC to AC transformers *do* exist, and are many times depicted by a dashed line (long stokes) on one of the wires (indicating polarized AC). Just take a look at the writing on the wall wart for the rating.

Although not used often, a "dashed line" (short strokes) on a DC to DC transformer are actually "-'s" (negatives).

A solid white line on DC to DC transformer wire almost always indicates positive, and usually (but not always) goes to the tip of the plug.

M


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## Moon Dog (Oct 3, 2006)

Yup, it's a true AC to DC supply... I have a few AC to AC adapters about as well.

There's always some sort of project that needs power! 

I already have a few meters around the house... I broke out my trusty Fluke 77 
and made sure of the polarity.

It never works to try and take the lazy man's way out...









Thanks fellas!


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## Mentalist (Sep 23, 2007)

Ok, good. Did not want anything to blow-up on ya!


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## gadget-evilusions (Jan 26, 2007)

Sounds like it's going to compltely depend on the manufacturer, I know all my jameco ac to dc wall warts have a dashed white line on the positive side.


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