The DPS5005 is a programmable power supply that takes power from a big AC to DC wall wart and turns it into a tiny bench-top power supply. You can pick one of these things up for about thirty ...

In the shack, [Helge] powers it with a bench power supply of his own design to provide ... This steps up the 12-volt input to 280 volts AC, which is then rectified, filtered, and regulated to ...

Capacitors with unique construction and failure modes are placed on the AC line to manage EMI modes and ensure user safety.