May contain traces of nut
Yes, because a 2½" drive doesn't need 12V so can be driven from the USB port as an external drive. It's not particularly relevant whether the internal power could run it, my aim is to find out why it's not running a standard drive.I wonder if you'll get meaningful results with a 2.5 (laptop) drive? I thought I had read previously some people use a 2.5 drive when the motherboard can't support a 3.5 drive.
What I need to do now, with replacement parts on such long lead time, is (with courage) swap U52 with one from a working unit and see whether the problem switches place (at risk of busting both of them). There are several other parts on the main board with the same TO252-5 package,