Sounds like it would not be a good idea to be tearing apart and fixing up old pinball machines in her/your nice little apartment. Playing noisy pinball machines may make things worse if girlfriend and/or neighbors next to you are not into pinball. Perhaps work out a deal w/ a friend who has space in an extra room, basement, or workshop. No comment if she fusses about you spending a lot of free time over at your friends house messin w/ pinball.