Well wait a minute. Just because it's crap, doesn't mean it has the right to exist. My yaxun made me a ton of money back in 2014. Back then there was flip phones, nokias, and very few iphones. It is still useful. I still use it to charge stuff.
First thing you do is check that transformer gives you power.
Then you check all the caps -- desolder and check ESR... You should have ESR meter. Here is a link to one --
click -- trust me, it's a money maker! If no ESR meter, replace all caps, but beware, new comes sometimes are bad.
Then, if that don't help. We'll look and see further.