I have a pair of Koss over-the-ear headphones that the dog has chewed the ⅛" stereo miniplug off of, and I would like to replace it. I bought a new plug at Radio Shack, and trimmed the three wires on the headphones, but I don’t which ones go where. There is a blue wire, a red wire, and a copper-colored (clear insulator?) wire.
Which ones are the right-left, and which one is the common? I am not so worried about getting the right and left reversed. I have tried looking at the plug that was chewed off, but it is molded around the wires, and my attempt to open it failed and removed all the wire connections. I have also tried plugging in the new miniplug and touching the wires, but I am getting no output.
The copper-colored wire is likely the common. It connects to the sleeve of the plug (the “contacts” on a plug, starting at the pointy end, are called tip - ring - sleeve). Could only guess which of the other two is which. You could attach the copper wire to the sleeve, one of the others to the tip or ring, then plug it in and see what you have (this is the dirty little secret of troubleshooting - trial-and-error).
If you can pop open the earpieces, then you can see exactly how its wired.
Get yourself a AA battery holder from RS (and a battery, too, of course). That copper-colored wire is most likely insulated with a clear enamel coating; you can burn it off with a match or lighter, then shine up the end with fine steel wool or emery paper. Then, starting with the assumption that the bare wire is common, twist the black wire from the battery hold to it, and while wearing the headphones, brush the other battery wire against one of the remaining wires. You’ll hear a pop or click in the side the wire goes to.