SMPS with shorted mosfet

[trondl]

It must be said that I am comfortable with linear psu's, but SMPS repair is new to me.

I recently found that my Ensoniq DP/2 audio fx unit was completely dead.
It hadn't been used for a while.
About 5 years ago I bought this replacement wall wart psu, as I bought it 2nd hand without a psu.
The psu was sold specifically for the Ensoniq by a US synth repair site.
It provides +/-12v and +5, so a fairly common setup.
Probably not important, but it has been feeding on Norwegian 230VAC.

First thought was to measure the psu output, and it was completely dead on all rails.
I then continued to open the wart and quickly saw that heat had taken place on the pcb.
The culprit must have been the K2645 n-ch mosfet, and my humble knowledge tells me that this is the pwm on the primary side.
Diode mode and resistance on dmm told me quickly that this had shorted in all directions, also out of circuit (Finally, my first failed transistor!).
 
Before even attempting to order a K2645 or equivalent, I fear something else may have failed here.
What should I look for?
I cannot see something resembling a fuse anywhere.
Since this happened on the primary side, could ugly things have ended up on the output on the secondary?
Must the SMPS be loaded to have any output?

Thanks for any advice!

[mariush]

You'd want to look for 2sk2645 or compatible  ... add the 2s in front . here's a potential datasheet: https://pdf1.alldatasheet.com/datasheet-pdf/view/60929/FUJI/2SK2645.html

Check every diode (the bridge rectifier, the diode after secondary transformer). Check every resistor... especially if there's a resistor directly connected to the mosfet, double check that dark green film capacitor.

Ideally you'd check the ESR of secondary capacitors with an esr meter. There's a to-92 component by that capacitors that's probably the voltage reference, make sure it outputs something.