If you have headphones with one earphone that doesn't work, you may be tempted to throw them in the trash. Often, though, you can repair them yourself with an ordinary soldering iron. Before you get started, make sure it's actually the headphone and not the device you have them plugged into that has the problem. If you're not familiar with soldering, ask a friend for help or stop by a makerspace or similar place for assistance.
Fix Headphones or Device?
If your headphones lose sound in one ear while you're listening to your favorite music or podcast, you might assume that it's a problem with the headphones themselves. It may well be, but it could also be a problem with the phone, computer or another device you use with the headphones.
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Before you reach for your tools, try using the headphones with another device or plugging another set of headphones or earbuds into your device's headphone jack. If the "broken" headphones work fine with another device, and a replacement set of headphones has the same problem with the original device, the problem is likely with the jack, not the headphones.
You may be able to solve the problem by cleaning dust out of the headphone jack with a can of compressed air or a cotton swap. Be gentle so you don't cause damage. If that doesn't work, research whether your device can have its headphone jack repaired or replaced at home or if you need to contact the manufacturer for help.
Fixing the Broken Earpiece
With one side of the headphones not working, the problem may be with the earpiece itself where electricity isn't flowing properly.
You can usually fix this with a soldering iron and a bit of solder. Gather a soldering iron, flathead screwdriver, desoldering braid and some solder in a place where you are comfortable working. Also, grab a wet sponge to wipe excess solder off the iron. Work in a well-ventilated area, especially if you're using solder with lead in it, and be careful not to burn yourself with the soldering iron. Don't be shy about asking for help or a spotter if you're not used to soldering.
Then, open the broken earpiece. You may need to pry it open with the screwdriver. Heat the soldering iron.
Look for a wire that's disconnected. If you find one, use the soldering iron and desoldering braid to remove any existing solder from the wire and its connection. Then, resolder it with new solder.
When the solder has cooled, reassemble the earpiece. You may need to glue it back together if it doesn't cleanly snap into one piece.
Fixing a Broken Plug
If the problem isn't in the earpiece itself, it may be in the plug. Grab a soldering iron and solder, wire strippers, scissors, a desoldering braid and a wet sponge to make this repair.
Snip the headphone wires a bit above the plug and remove any casing from the plug itself. Heat the soldering iron. Remove any existing bits of wire from the contacts on the plug using the desoldering braid and the soldering iron, taking note of which color-coded segments of wire connect where. Strip the insulation from the ends of the newly cut wire.
Reconnect the appropriate color-coded sections of the wire to the corresponding parts of the plug using the soldering iron. Wait for the solder to cool and replace the casing on the plug. Test your newly repaired headphones.