dell latitude e5530

I have an E5530. The left speaker does not play equally loud as the right speaker. When I go to Hardware and Sound/Sound/Configure and click the "Test" icon the left speaker is clearly not as loud as the right speaker. I have disassembled twice and see nothing wrong except that one of the wires...

My Dell Latitude E5530 came with an i3-2328m. I just upgraded to the i7-2640m. Both are at 35 TDP and are Sandy Bridge, so no problems. 16GB of RAM. Both cpu's are in the list: https://www.cpu-upgrade.com/CPUs/Intel/Core_i3_Mobile/i3-2328M.html This guy upgraded his E5530 cpu (whatever it was)...