I have tried to solder on this cable but have failed. Its an extremely difficult solder job. The most Ive gotten was that I could turn the ipod on and one of the volume buttons worked. The ipod would not turn off and the other volume button was unresponsive. The reason this is so difficult to do is because there are 4 solder points on the cable. I assume one for each of the functions of the cable. If either: 1) you dont get the solder through the tiny hole, 2) any of the 2 solder points connect through solder either on top or under the cable, or 3) the cable has a tear in it..... if any of those occur something will not work. You might get 1 or 2 out of 4 but not all 4. The holes are just so small and they are so close together that you need to be precise 4 times in a row because once you mess up you need to start all over.
Good luck! Very very difficult fix.