Here is another puzzle.
I replaced the USB Port because it made a bad connection and checked continuity between the plug of a cable and the components on the port. All seems ok with the USB port.
U1, D23 and the trace near U1p3 were all scorched. I replaced U1, D23 and ran a jumper from p3 to L2. The board works ok with batteries, but has no power with USB.
I can measure 5V at C7, but nothing at pin3. On a good board I get 3V there. I did this repair on 3 boards with the same problem, but it worked only on one board. What could it be? Is it a bad U1 chip?
These are from a job lot for repairs, but turned out it was a box of junk where the seller assembles the devices with components that he couldn't repair.. I managed to fix most of them so far but they were incredibly hard to fix. Good thing is I learned so much from trying to fix these