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You've most likely got a shorted switching fet. This may be a standalone fet, or the fet integrated in the power supply IC. If you probe across the pins of the main filter cap (probably a 400V at around 47uF) and find a short this is almost certainly the case.
If it's an IC with an integrated fet they usually don't take anything else with them when they short other than the fusible resistor. If it's a discrete FET with an IC controlling it they can take the IC with them. When they short there will be 300+ VDC on the gate in the brief period before the fuse blows. There are usually diodes/resistors bewteen the output of the IC and gate pin and often they go saving the IC.
Pictures of the board will help if you're still lost.
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