Still searching for a faulty component in the power circuit, and
nothing seems to be wrong?
Search for a (very) little transformer on the printed circuit board (or
nearby) and for a fuse attached to it. Should one of these two fails,
the whole thing stops working, because this sub-circuit is user for
detecting when the mains power is on. Probably, this transformer has a
built-in thermal fuse that trips when it reaches 110Cº, so check
resistance (its about 50 Ohm for 230 volt mains). The other part to
check is a fuse in series with this transformer, but maybe you have a
hard time trying to identify it, because its encapsulate is sometimes
very similar to a diode bridge, and others seems to be a resistor in a
yellow or green body, but with very strange or no markings at all.
Manufacturers tend to be very creative when choosing this fuse, and its
my believe they do it on purpose.

Hope you can "bring it back to life".
Greetings
Louis.