You think if I polarized dad's stereo no more shocks would happen?
Depends. Manufacturers back then sometimes had bypass capacitors going from each side of the incoming power line to the chassis, in sets with power transformers. Something like 0.05uF. They were intended to reduce line sourced noise. Some sets have the power switch on one side of the line, and maybe a fuse holder on the other side of the line. With a non-polarized plug, neither side could be expected to be the neutral, and this gave the manufacturer tie points for the transformer primary leads (one on the switch, the other the fuse holder), and thus saved on having to have an extra tie point. Using a 3 prong plug, and connecting the chassis to the ground would be a good solution, but only if there is isolation provided by a power transformer.
In a "hot chassis" set, the power switch was almost always on its ground. This made the wiring dress a little easier, in that there would be no 120VAC (with respect to the local "ground" of the set) around the audio signal wiring (the power switch usually part of the volume control). Also, the switch contacts may act as a fuse of sorts, a fault current from the chassis to a real ground could burn them up and clear the fault, however the switch would never work again. In any event, a polarized plug should connect the neutral to the chassis, and the switch on the hot side. (to reduce any hum pickup from the new switch wiring, wrap some insulated wire around the hot wires, and ground that wire somewhere to the chassis. This creates a shield. Of course, a 3 prong plug is not usable here.
[This message has been edited by wa2ise (edited 12-18-2006).]