Just because a few lights turn on doesn't mean the power supply is good. The power supply generates +3.3v, +5v, +12v, -12v and +5vsb.
The +5vsb is +5v standby. As in, this is the power for the lights while the computer is turned off or standing by.
The +5vsb is +5v standby. As in, this is the power for the lights while the computer is turned off or standing by.