Hard to diagnose these problems over the intrnet site unseen, so it may take a few posts.  Heres a few things to check:

1.  It is normal when you turn on a Gottlieb game that it goes straight to tilt until the first game is played.

2. Is the humming coming from the knocker coil?  When it hums check if it is this coil that is energised. There is a contact that makes on the credit wheel as it gives a credit that energises this coil.