I had the exact same problem on my Siren 4GB MP3 player and I decided to give it a shot at fixing it myself. I figured - if I messed up something internally while I tried to solve the issue, it wouldn't be any worse than an MP3 player that only played in one ear. As it turned out, it wasn't that difficult to fix (only took 30 minutes) and I learned a little something about the inside of my Siren. There were only four tiny screws that I had to remove in order to access the inside of the player to take a look at the headphone jack. I took two screws out from the inside of the battery compartment, then I was able to unsnap the cover off of the player. I removed two additional screws from the bottom of the board inside, which allowed me to remove the plastic backing. Once I was able to examine the headphone jack, I noticed that there were six spots in which the jack connects to the board. For me and my player, at one of those six points, there was a very tiny crack that needed to be repaired. I heated up a soldering iron, one with a fine pointed tip, then carefully mended the crack. With my Siren, I was still able to insert a battery (hold it in place) and play music with the player disassembled. This helped me identify where the headphone jack was malfunctioning, and in the end, I was able to check if the soldering had solved the issue. In my case, it did, and I was surprised how easy it was. I put the player back together and haven't had any problems since. I hope this helps you, good luck with yours.
Jackson, September 2007
