Help identifying positive and negative please. (1 Viewer)

Badknee

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bought a freeview recorder at the weekend so that we can load it up here and watch when away. I was expecting it to be 230volts which is ok but delighted to find its 12v.

Now the question, I want to cut the transformer off the power cable but wondering which might be the positive and which the negative?

Any ideas please as its not colour coded?

image.jpeg
 

Chris

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eeny, meeny, miney mo....


Works for me.

Well, roughly half the time it does.
 
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Apr 22, 2013
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Isn't there a little diagram on the unit, near the connector?
Or else in the manual.
 

tonka

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The centre pin is 99% of the time the +ve.
Do you have a multimeter ?? If so you can use that the find out..

Also as said above, it's often shown near the socket the plug connections. Once the wire is cut you can use the multimeter to establish which wire goes to the center and which is the outer -ve..
 

Techno

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Yes Andy I thought of that but will it tell me which is - and which +?
If you put your red probe on the centre and black on the outer it will either read a voltage or a minus voltage -12V if it reads minus it is reversed.

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Or open the box up and see where the wires go. The live one may have a little glass fuse
 

Techno

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Once you know which is the positive for sure you can then do a continuity test after cutting it off
 
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Badknee

Badknee

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Or open the box up and see where the wires go. The live one may have a little glass fuse
The box and the plug are sealed that's why I me stumped :(
I'll dig out my multimeter. (y)
 
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The box and the plug are sealed that's why I me stumped :(
I'll dig out my multimeter. (y)

Aye. Stick a pin through the one with the tracer and see if you are getting 12v running up it. I think the units case should work as a ground unless plastic.

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Badknee

Badknee

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If you put your red probe on the centre and black on the outer it will either read a voltage or a minus voltage -12V if it reads minus it is reversed.

Yes bang on as usual Andy. The wire with the long dashes on it is + so I can get on with wiring it in now.

Thanks for all your replies and help lads, brilliant as usual.....





Well exept that @eddievanbitz when he's on a bender........

:whistle2::rofl::rofl::rofl:

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movan

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Don't know why you wasted your time with this lot ... should have asked a blonde in the first instance.
 
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Badknee

Badknee

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Don't know why you wasted your time with this lot ... should have asked a blonde in the first instance.
Errrrrrrrrrrrr, some would say I was having a blonde moment. :blush: :whistle2:

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scotjimland

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I think every schoolboy / girl has done this at one time or another in science class. . .. to test the polarity of a battery..

attach a wire to both +pos and -neg. cut a potato in half, push both ends of the bare wire into it , quite close together.. the negative wire will get froth around it.. this is due to the Hydrogen gas being produced.. wait long enough and the positive wire will turn the potato green as Copper Chloride is formed.

please don't try this with AC mains.. it boils the potato ..

buy would also prove that AC has no polarity .. both wires fizz
 
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