How do I know if my guitar jack is bad?
Humming or Buzzing
If, when you insert your cable lead into the input, there is a deep humming tone or loud buzzing sound, it may be an indication that the input ground wire may have come loose. The buzzing or humming is similar to when you touch the end of the lead to a metal object.
Why is my guitar jack not working?
Assuming that you don't see any loose wires, the first thing to do is make sure the socket is holding your jack plug securely. ... Test-fit your cable and see how secure its plug is in the socket. If the plug wiggles around or falls out then that long metal clip will need to be adjusted.