First of all, he does realize that the volume control is on the little metal stick on the box on the right, just inside the coindoor? (Sorry, I'm not technical enough to know the real names.) When I first got my DE and Sega games, I was looking for the volume control on the menu and couldn't find anything there except background override, and later found out about the volume control stick/knob.
If he knows the above and it still isn't working, then I'm not sure and hopefully this bump will get someone more technical to see it and help.
