[mikethedruid]

Were it my radio, I would check using an ohm meter to see which of the two "prongs" was connected to the chassis. I would connect this prong to the wide blade lead, (neutral, or 'gounded') and the lead from the narrower blade (hot) to the "prong that did not connect to the chassis. This would ensure that the chassis was connected to the grounded side of AC. In U. S. electrical distribution, for the 120V receptacles, the wider blade is supposed to be at the same potential as the ground (U shaped) blade. They both connect back to the ground bar at the fuse or breaker box, the wide blade through the white wire in the house wiring to the receptacle, the U shaped blade through the bare, or the green wire in the house wiring.