Voltage conversion from 220V to 110V.

Jea48...Polarity of the AC power should be of no concern because the rectifier makes it into DC anyway. Power transformers that I have worked with don't even identify the primary and secondary winding wires as to polarity, so, short of running a test on every transformer as the equipment was being built, it is not always the same from unit to unit.

I remember when there were cheap table radios (and some other stuff) that had no transformer, and the metal chassis would be hot if the plug was in one way. Furthermore, the 2-prong plugs were not polarized either. These devices relied on their plastic cases to protect the user, but sometimes an exposed screw would be hot. The occasional tingle kept us alert!

El...tingle? I remember working on an old ( tuber back as a teen in the mid sixties, dutifully keeping one arm behind my back to ensure not closing a loop. Two hours later I woke up 10 feet away on the floor, with a bump on my head.
Later I noticed a red scratch on my neck.
Next day I returned to my basement lair and saw a piece of 16 gauge dangling at head height from a waterpipe as my "convenient" ground. But recently I taught my daughter (17) how to replace a duplex while still "hot"; jeez, ya think I have a subconscious motivation to avoid all those tuition bills? PHEW!

A schoolmate of mine nearly killed himself (really) with a Heathkit Geiger counter. Although the construction manual warned about the high voltages he figured "four D cells...how dangerous can it be?" Well those D cells fed a chopper and voltage step up circuitry whch produced I don't know how many thousand volts, with substantial charge stored in capacitors.