Hi,

If the case is cracked there, it may also be that the audio socket has come loose from the systemboard.

Do you get “stereo” audio or only “mono” audio output for the headphones?

Try adjusting the audio to left and right speaker to check if there is audio for both channels.

If only for one channel here’s a link to the service manual for the laptop. Scroll to p.54 to view the necessary pre-requisite steps and then the procedure to remove the systemboard.

You may not have to do all this, just do enough so that you can inspect the socket to check if it is loose or not or if there is any damage to the systemboard around the area of the crack.

If all appears to be OK it still could be a problem with the socket itself. As it is directly mounted onto the systemboard you’ll need smd soldering skills and tools to replace it. Unfortunately i have not been able to locate a replacement socket (if it is the problem). You may have better luck.