I hate to inject myself in an old thread, but it's related. I also purchased from Ebay (Sept. 2013) and just began to have issues with the left ear phone. I had noticed it prior to this, but it was very rare and I had chalked it up to a loose cable to my phone/mp3 player and or gym sweat.
Needless to say, the left phone is now nearly completely silent. If I tap it, the sound does return briefly but then returns to silence. Naturally, I suspected a connection issue on the inside, so I removed the cover to have a look.
No readily apparent contact issues - the solder joints are still solid. I tested ground & the left channel w/ a multimeter and both seemed to check out fine. I think it is dead, but if anyone has any other troubleshooting ideas, please let me know.
EDIT: Thought I'd add that I went ahead and re-soldered the joints to make sure. Same result. It seemed that pushing/tapping on the cable around the strain relief made the sound cut in/out. Next, I cut the wire below the strain relief to make sure the cable wasn't defective within. Unfortunately, again, it was the same result. There's continuity throughout both strands of cable, but sound is only produced occasionally if I tap/push the driver. I guess it's time to start anew the hunt for gym/commute headphones.
Edited by Devcon - 1/1/14 at 3:27pm