I was working on a project wherein I was soldering 2 severed USB charging cables (2 wires per cable), a micro-USB to a standard USB. But when i had linked the wires together with a generous amount of solder, which did adhere to the wires quite easily, the wires did not connect or at least did not have a low enough resistance for enough current to flow. Could this be an issue with the soldering joints, or is it a problem with the wires inside the insulation having disconnected? I did get these wires from a "broken" USB charging cable which i needed to shorten, so I'm really not sure what the problem is.

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    \$\begingroup\$ Grab a multimeter and check the connections and resistances. We really can't help you on this one. \$\endgroup\$ – Eugene Sh. Sep 15 '17 at 14:55
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    \$\begingroup\$ Did you flux the wires before soldering them? Chances are if the conductors aren't actually broken, then you have too much oxidization on the wires and the solder is only sitting around the outside. \$\endgroup\$ – DerStrom8 Sep 15 '17 at 15:00
  • \$\begingroup\$ i'm fairly certain my solder had flux in it, and when i made the connections, there was a bunch of it that flowed off and made a little puddle, so it's likely that the wires got plenty of flux on them for good contact. \$\endgroup\$ – malachik Sep 15 '17 at 15:10
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    \$\begingroup\$ Were the wires tinned properly? If they are like the wires in headphones they may look like shiny copper but they are coated with insulating varnish. This has to be burnt off and they have to be tinned (look shiny silver) before soldering. \$\endgroup\$ – Brian Drummond Sep 15 '17 at 15:14
  • \$\begingroup\$ that was my suspicion, but i thought i could melt it away with my soldering iron. i guess not; the wires looked like copper and not tinned. that was probably the problem. thanks! \$\endgroup\$ – malachik Sep 15 '17 at 15:52

Delicate cables can not only fail easily but fail in more than one place. Basic continuity should be there or discard them both and use new ones.

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  • \$\begingroup\$ yeah, i figured out that it was an issue with the cable itself or one of the plugs, neither of which i can reliably fix. I learned a lesson, though: don't try to build working things out of not-working things. \$\endgroup\$ – malachik Sep 18 '17 at 12:28

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