Just to add.. i had 1 machine come through my hands that was lethal. I was repairing it for someone else and ended up buying it.
But when i got it, you would get a shock from the door and lockdown bar.. it was mains voltage.
Now this game came from a very well known dealer fully working and overhauled. The leaf switches on the door had been altered so coin switch would activate just before the start button.. so in essence, the two switches had been combined.
Game was a 60's WMS machine and these have mains through the loom behind the door also... wiring on one side of the AC cycle had worn through and caused the door and any subsequent metal attached to be live with half AC cycle.

Its important to earth and have trip switches installed... all my machine to machine cabling is on RCD devices... and then further up the line i have the main earth trip. Thats 2 RCD devices just in case 1 decides not to work