Just based on your description, it is probably one of the computer components, with the computer power supply being the most likely culprit, although, it could be any number of things.
But it is not lack of phone line. A phone line or internet connection is only needed to connect to an online server, for tournaments, etc. The manufacturer (Global VR) no longer has a running server to support online play of this game. But a group of enthusiasts have managed to make there own private server. Check out the PGA Tour Golf by Global VR & EA Sports Owners Thread for more info :
http://forum.arcadecontrols.com/index.php/topic,129168.msg1701773.html#msg1701773.
They've also formed a Facebook group, if you're on FB; PGA Tour Golf by Global VR & EA Sports Owners Page - Online . They can probably help with any questions you may have, even if you're not looking to get your cabinet online.
Penbo