FWIW my serious is advice is do not work on your game with the power on, and preferably unplug it as well (you can get shocked by some (most?) EM's even with the power switch off...)
And reading about someone blowing up their ACDC by having a tool (or the mini playfield?) fall on the transformer and make something "go boom" has had me since advice noobs to unplug the game...
Not that veterans are immune from doing stupid stuff, it is just that most of us have "broken" something by working on a powered on game so even the slow learners have this one sorted out after a decade or two