SB = Stand By, or "always on"
Every power-supply provides 5V to the board on a single pin in the 24pin ATX connector. the 5VSB pin.
This rail is always on, as long as the psu is physically switched on and connected to the mains. This rail is essential for the board since all the logic and components needed for the board to turn on the PSU is powered somehow from that rail.
And yes, in case you can figure out what broke, you can most likely fix it with reasonable effort.
But if it isn't your fault, i'd RMA it.
Every power-supply provides 5V to the board on a single pin in the 24pin ATX connector. the 5VSB pin.
This rail is always on, as long as the psu is physically switched on and connected to the mains. This rail is essential for the board since all the logic and components needed for the board to turn on the PSU is powered somehow from that rail.
And yes, in case you can figure out what broke, you can most likely fix it with reasonable effort.
But if it isn't your fault, i'd RMA it.