The capacitors on these power supplies are notorious for leaking acid as the 5v. There are two capacitors to the lower right of the heat sink I'd be removing these.
If it stinks when you heat up the solder your caps are stuffed
+1 to Daniels advice, just replace them
I had the same issue with a Jurassic Park i restored some time ago, ie not booting.. replacing all the caps to do with the 5v regulator circuit fixed it
Just about ALL of the electrolytic caps on the board had that smell when the leads were heated up.
My old boss used to call that smell the 'cat piss' smell
