The secondary has a lot of hi rated quick rectifier diodes, a bunch of low ESR capacitors and the feedback side has 1 controller chip, possibly along with a TL494 chip and it will be hooked up to an optocoupler wired to the switching elements on the primary. If the opto dies, the supply wont work, same as with the controller chips. Since u have the fuse intact, power up the smps and check for 5 volts on the VSB line (purple wire), then check all caps on side near from where the wire bunches are soldered. That is the secondary side. remove caps from pcb before testing. on circuit will show a false closed ckt due to the transformer's secondary impedance. Also beware that the huge caps on the primary can hold a lethal charge even after u disconnect the supply from mains, check with a multimeter and discharge with a ac bulb if necessary.