never seen one of these, but it isn't blowing mains fuses, so SMPS main circuit working ok, and it's a "trivial" problem on one dc output. If you can't find it yourself, then you really shouldn't be attempting this type of repair. There's 350v dc around the mains transformer, and it can kill you !!!!!
That said, possibilities are:
1) Is there a 12v regulator ic, 7812 or similar? If so, and 15v dc going in but nothing out, then replace. If on heatsink, careful about replacing insulating washer! If this blows again, suspect leaky decoupling caps elsewhere on main board, it'll run hot a while then just expire.
2) Or could be 12v rectifying diode, gone open circuit. Safest to check when depowered, but probably impossible when in circuit, in which case check for dc volts either side, if not getting through then replace. Again, if this blows again, probably the rectifying cap leaky, good idea to rplace this anyway!
3) Or that transformer winding gone open, extremely unlikely but possible, check for ac volts, if none then transformer needs replacing.
Also check wiring and connectors, if a dc fuse present and blown then needs replacing, but another fault also present, etc.
