A serious power surge will usually blow the varistor right next to the line
filter in solid state machines and protect the electronics of the machine.
If the varistor blows it will short and blow the fuse next to it. That fuse
will appear to violently blow, splattering the inside of the glass tube
with molten metal. You can easily test if a shorted varistor is the problem
on most solid state machines by unplugging the transformer and see if the
fuse still blows when the power cord is plugged in.
Note that since the varistor normally does not conduct, so you can
temporarily clip out the shorted varistor, replace the blown fuse and the
machine should work fine from there. CAUTION: Do not do this as a
permanent solution, since this leaves the electronics of the machine exposed
and vulnerable to power surges. I recommend you only do this to verify that
the rest of the machine is okay.