Hi Ric,
I have a Gottlieb 'Top score 1975' which is a similiar layout to 'Soccer 1975'. Both have the same backglass animation, kick out holes etc. Your problem could be as simple as a switch not making or a connection. Here is a part scan of a 'Top score' machine where you should be looking first. Not sure if this can help as may differ to your machine schematic, however gives you some direction. I have circled some areas where you need to check.

Greg