Wall warts,
least here in USA must be fused internally or have a thermal
interupter (usually the blow open). I've forcably opened a number of
warts to replace protective devices.
I've opened up many wall warts over here and found the the transformer
primary winge goes straigh to the tags on the transformer (no obvious
connections to a fuse or thermal fuse) and those tags are wired straight
to the mains plug pins. And yes, said wall wards have various approvals
written on them.
I was told that the transfromer primary is supposed to fuse safely in the
event of a fault. My experience is that it doesn't (I've had shorts on
the output side cause the plastic case to deform and much magic smoke to
come out, but the transformer primary was still continuos after I turned
the power off. I did not feel like seeing if it would ever fail).
-tony
Actually, fire came close for mine. :O
I had DSL modem's big ceramic capacitor short out across the 16V AC
input and fry the wall wart transformer. Cut it open, interior all
smelly and softened, primary winding opened where wires attached to
blades. Exterior is mint.
Fixed this with a junk VCR gutted except for transformer with a fuse
& new ceramic capacitor in DSL modem. Been this way for 3 years.
Cheers, Wizard