I'm repairing owon pds5022 where the power supply is bad. The U3 chip is burn beyond any real markings. It is 5 pin smd, SOT-25 package. I've drawn the schema on paper and it looks like pin3 is input ( fed via resistor), pin2 is ground, pin1 could be feedback. Pins 4&5 are connected together and act as output, there is also connection to pin1 to connector with small condensator and inductor. The markings are so small that I cannot read them even with magnifier glass (I'm getting old:-( ) , need stereomicroscope to read them. The U3 could have markings 510B but cannot tell if that's correct. The B can also be some manufacturer logo, code could also be upside down.
I've ruled out a couple smd regulators ( Torek brand ) , any idea what component could really be ? Owon has not answered to my query.