Ang psu pwede i power on test na walang main board sa pamamagitan battery, at dun malalaman kung gumagana ang power On triggering na mag ppa oscillate sa chopper.pwede rin gamitan ng standby 5 volts kung available sa board.
the battery serves as a supply to Power On, because there's no motherboard, And the positive ot battery connect to power On pin in power supply to oscillate the entire secondary section