That is all that a power supply does i.e. supply power, rectify it to DC ( in most cases ) and regulate it so that it is steady.
Judging by what you're saying, much of the "power supply" is actually inside of the transport. The parts that you mentioned will not rectify or regulate the voltages necessary for proper operation. They probably did it this way as AC isn't as lossy to feed over any given distance. On top of that, placing all of the regulators further away from the circuitry would make it slower to respond to changes in the voltage, reducing its' effectiveness. At the same time though, they moved the transformer away from the circuitry, which can DEFINITELY lower the noise floor of this type of component. Sean
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