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My friend accidently stepped on a wire for his light and the tension broke the adapter's connector - I told him I'd try to fix it. I've already cut the connector off and have readied my replacement. I plan to use solderless connectors but as the original connector colors are unfamiliar I want to check with this site about how to check for which wire is power and which is ground.

Can I use my multimeter to check which wire is power and which is ground? If so what setting do I need to use?

The adapter: AC adapter

The new connector: enter image description here

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  • \$\begingroup\$ In the first picture we can't see the insulation of one of the wires to identify it. Hold back the outer cordage layer and take another picture. The connector is DC. The easiest method of figuring this out may be to meter the device to verify which is + and which is -, then use continuity to see which color connects to the inner and outer parts of the barrel connector, then meter your new connector and match them up. If you want a nicer looking result you can probably find a solder on barrel connector that you can have the cordage layer go right into. \$\endgroup\$ – K H Sep 12 '18 at 1:46
  • \$\begingroup\$ Just looked that up. If it is, indeed, a $350 desk toy, you should get a better looking connector. \$\endgroup\$ – K H Sep 12 '18 at 3:25
  • \$\begingroup\$ @KH Not to mention thicker wires \$\endgroup\$ – Maple Sep 12 '18 at 9:04
  • \$\begingroup\$ @Maple good point. It's only an amp, but those look a bit anorexic. \$\endgroup\$ – K H Sep 12 '18 at 23:28
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The power supply has the output label. Center positive for the barrel connector, 15V DC.

Yes, you would/could use your multimeter to measure the two wires, and determine which one is positive using the voltmeter feature (In DC mode if it has both AC and DC). Also use your multimeter's continuity test or ohmmeter feature to confirm which wire on the replacement connector goes to the center pin and outside of the replacement connector.

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Yes red =+ , Blk=- or 0V. Measure the positive voltage and match to Red.

Connect and use strong (packing?) tape to mechanically secure the pair of connectors. A common test is a 5lb pull test for reliability.

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If you do not want to solder, at least use something more reliable than that flimsy plug with tiny internal contacts. Something like this, for example. Extremely easy to connect and has polarity markings for center-positive connection (same as your AC adapter).

To find output polarity put multimeter in DC voltage mode, measure adapter output. If the reading is positive (should be around 15V) then the wire connected to multimeter's red input is "+". If the reading is negative, then the wire connected to red wire is "-".

enter image description here

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