240-12v adaptor, Which wire is positive?

[gardeners26]

I have a standard mains adaptor switchable from 3 to 12v. One wire is black and the other is black with a white stripe. Which of these is +ve ?

 

[plugwash]

probablly the one with the stripe but best to test it.

 

[Steve]

doesn't it have a polarity switch on it anyway? A lot of these multi-adaptors do, because some items have centre-positive input and some have centre-negative input. Use your multimeter

 

[ban-all-sheds]

I have a standard mains adaptor

There is no such thing...

 

[Nickthedentist]

Yep, get a multimeter or you could end up frying whatever you connect it to (or the adaptor itself if the device has a protection diode wired "backwards" across its input).

A really cheap one would do for this - well under a fiver if you look around.

Cheers,
Nick.

 

[gardeners26]

Thanks to everyone-borrowed a mulimeter-the black and white wire was positive and the appliance is working fine. Thanks again. ROY