[scudder]

Most of the replacement headphone ribbon cables come wired incorrectly. This give the 'headphones' mode when they are not pugged in and vice versa. The solution as touched on earlier in the thread is as follows:-
Before you fit the cable (or if you have already fitted it - open the case again - should be easier second time around) take a flat head screwdriver - watchmaker type is perfect.
Hold the headphone socket so that you are looking into the end with the brass fitting which goes around the top and right hand edge. Gently prise this away from the right hand side so that it clears the internal contact breaker. Now that piece is out of the way, use the screwdriver to push the internal part of the breaker towards the left hand side of the socket. It will bend with a bit of effort. This should leave the internal breaker sitting in the centre of the socket. Now, relocate the brass outer contact and put a dab of superglue there to keep it in place as it will be under a slight stress when you insert your headphones. First couple of times you push in the jack it will feel tight, but this gets easier with use. Wait until the superglue has dried before testing. You can test without screwing everything back together, just connect to the motherboard and push in the jack. Be careful, you can easily break the ribbon cable as it is fragile.
Job done!