Self created problem

[rocky28965]

I am having a tidy up with the wiring behind my radio stack.
In doing so I shortened the cable on a USB hub.
I have crimped fresh terminals on the cables but didn't take note of the polarities.
Both wires are black, so there is no way to tell one from the other.
Short of breaking the unit apart, is there any way to identify negative and positive.
The unit is "mbeat MB-USBC480 4-Port 40W rapid car charger"

 

[jtwalker]

The black wire is positive, and the other is negative.

 

[mmckenna]

Short of breaking the unit apart, is there any way to identify negative and positive.
The unit is "mbeat MB-USBC480 4-Port 40W rapid car charger"

Oops, you are in NZ, had to redo this.

Here in the states, we have Harbor Freight. They sell discounted tools. Up here, they sell a basic multimeter for about $8USD.

I know there's similar shops down there. You'll do yourself a favor by having one, it has many uses in the hobby and you'll thank yourself in the long run. It'll pay for itself.

 

[KB4MSZ]

The black wire is positive, and the other is negative.

That sounds like something I would say.

 

[rocky28965]

Interesting replies, but no great solutions.
I do have a multimeter but how would that help to find the polarity.

 

[VK4PJF]

Interesting replies, but no great solutions.
I do have a multimeter but how would that help to find the polarity.

I'm unclear on whether this cable is attached to the hub, to the power supply or is a cable that's detachable at both ends.

If it's attached to the power supply, remove the other end from any other equipment, power it up, and use the multimeter to measure the output.

If it's a fully detached cable, test continuity on one wire. Test continuity on the other. Ensure both match the expected layout at both ends, e.g. they're not crossed over in the connector.

 

[rocky28965]

If you google the description of the device, you will see what it looks like.
The cigar lighter plug has been removed.
Everything else is still intact.
Both wires are the same color.

 

[wtp]

have you tried to contact the maker ?
their website has a contact us button.

 

[rocky28965]

No, hadn't considered that.

 

[mmckenna]

Interesting replies, but no great solutions.
I do have a multimeter but how would that help to find the polarity.

The multimeter will have a negative test lead and a positive test lead. If you put the black lead on one of the black wires and the red lead on the other black wire, it should show the voltage.
If the voltage shows positive value, like 5.32, then you know you have the red lead on the positive and the black lead on the negative.
If the voltage shows negative value, like -5.32, then you know you have the red lead on the negative and the black lead on positive.

 

[rocky28965]

Thanks for the help guys.
I got it sorted finally.
I cracked open the case and traced which wire went to the earth track on the circuit board.

 

[IC-R20]

Thanks for the help guys.
I got it sorted finally.
I cracked open the case and traced which wire went to the earth track on the circuit board.

Self created increased difficulty.

 

[rocky28965]

Sure was, I should of marked the cables before I cut off the plug.
I'll blame it on old age and oncoming dementia.

 

[RoninJoliet]

Your not alone buddy ☹️

 

[es93546]

Your not alone buddy ☹️

Ditto!