I don't have the PCB in front of me but is U301 the component with the large heatsink?
I picked up a Play 3 that was dead and the digital power switch had exploded. The part number was FSQ0565R which I couldn't find anywhere without waiting over a month to be shipped from China so I bought the same component with beefier specifications FSQ0765R from everyone's favourite auction bay.
In addition to replacing this IC, the fuse was also busted. It is a tiny brown cylindrical component next to the power plug. Something like 2A 240V on the label. I just temporarily jumpered the fuse and everything started working.
Good luck!