Thats a nice, beefy Unregulated power supply you got there, Perfect for CNC. The thing between the posts on the big capacitor is a bleeder resistor, it slowly takes the charge out of the capacitor after the power supply is unplugged or shut off, Usually to prevent shocking yourself, or welding a metal tool between the capacitor terminals while working on or around it after it has been unplugged.
The most efficient way of dropping the voltage would be to take a turn or 2 of wire off the secondary coil of the transformer, nearly impossible unless you wound it yourself.
Capacitors in Microwave ovens have been known to kill people months after the thing was unplugged, but they are storing many thousands of times more voltage than yours.
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