If you have headphones that are not working properly, you may be inclined to simply get rid of them and go purchase another set. However, before you completely abandon your old Sony headphones, there are a few troubleshooting steps you can take to try to fix them.
Plug another pair of headphones into the device you are trying to use, to make sure it is indeed the headphones that are malfunctioning. Many times, it is the device that is not working, so it is a good idea to double-check the malfunction before continuing.
Look over the entire length of the headphone cord and check for exposed wire. If you find any, inspect it to see if it is frayed. If it is, you will need to replace the headphones. If not, you can simply wrap electric tape tightly around the exposed wire to restore functionality.
If the headphones are wireless, make sure they are still synced. As with other wireless devices, if headphones are not used for an extended period of time, their wireless power will diminish and the connection will need to be reestablished. Consult your user's manual for exact directions on how to re-sync your headphones.
Take a look at the headphone jack. If it has been severely scratched or bent, you will need to replace the jack. This will cost some money, so if you bought a cheap pair of headphones, it may not be worth it. But if you do want to proceed with the repair, do so by purchasing an appropriately sized jack (most headphones use the 35mm standard) and then using a pair of electronics scissors to cut the original one off at the wire. Then solder on the new jack with some plain audio wire and wrap the new cords in electric tape.