"Hey (to Matt) You don’t need to worry about any danger as long as there is a power pack between you and the wall socket.

In other words, if there is a separate power pack which plugs into the wall (you know the sort of things I mean – AKA ‘wall wart’) and if this power pack feeds the main circuitry via a power lead, then there’s no actual mains anywhere in the main circuit at all and you can’t get hurt. The worst that can happen is something goes POP. ;-)

Dave J."

This is a very old thread, but I thought it would be best to point out that the wall wart for the NES is an AC step down transformer with no additional circuitry. That means that this device is most certainly connected to mains at the power supply circuit inside the system. Additionally there is no "earth" or casing ground prong. Be safe and stay away from the psu unless power is disconnected!