Bricked jack port [lineout anyone?]

Hey there.

A while ago my left sound went away but my earphones were working fine on other players, so I figured the problem would be the audio port. I opened up the player and soldered a wire from the three connectors up there, back through the audio port and outside the player I soldered another seperate female connector. This worked somewhat, yet it still stuttered when I move the cable too much. So, I figured it was the connection between the circuit board and the audio port.

Now I took off the port completely but it had 4 connectors whereas only 3 are needed. I am not looking forward to trial and error because I'm not all too comfortable soldering dots on a six-layered PCB. Does ayone know where the audio signals come from? Or maybe someone has a detailed lineout of the PCB? I couldn't find any.