My son found this arcade himself, and having recently
Gone through a divorce I thought this project to
Be a great thing for both of us to work on.  We got it completely cleaned, trackball
Mechanism cleaned, monitor replaced, and even fabricated a new door for the base of the cabinet.    
The only thing we can’t get working is the sound.  I have went into the menu and made sure it was turned up.   I tried swapping in a new speaker without any change.  I have a cheap voltometer that has a red light when it detects a charge.   Where the sound plugs in it does not light up (all other connections it lights up fine)
Anyone have any ideas, or things to try next?