I use a caliper and run it up and down large electrolytic caps looking for bulges that my eye may miss.
Until a fusible link is connected across a blown fuse, not much of anything can be diagnosed.
Da nose can sweep across the board and da nose knows. Personally I would sweep the opened unit with IR especially across resistors if the unit progresses to a checkout stage under load.
I treat mine as a 13.6 volt fixed 55-amp power supply. Nothing less, nothing more. Totally open frame and getting blasted with two fans can't hurt.
Realize your "converter's" weak points and deal with it. Going from a "Doesn't Work" to an "Almost Works" for 200+ dollars just does not cut it with me. Oh I see a few of you demand the obligatory caveat. For Off Grid Boondocking Use.
Don't think I'd need the BORG nor the LIFELINE if I should check into the St Francis Hotel in SF or The Coronado Inn in San Diego, either.