Quoted from Friengineer:???? You should never use wd-40 on or near your pinball machine with exception only to the leg bolts, maybe. Replace the rusty components. Wipe up any extra WD-40 before you turn the game on again & probably should keep it off for a bit...
Just read on the AC/DC thread someone using WD-40 on the ramps. Personally I would think this would get all over the balls and then all over the playfield, etc.