No power on USB port.

Hi,

My macbook air (A1304) has no power on it's only USB port. But the rest of the port is fully functional, so if a device is powered externally, they work just fine (same for externally powered usb hub's).

I've done some digging into machine and here's what i got. Instead of standard 5V, the power line has only 1.25V (just as the signal line). The port hatch is in good shape and the plug and sockets connecting it to the logic board are clean and have been refitted. The connector tape running from logic board to the port seems ok (tested with multimeter for conductivity and short-circuit). Resetting PRAM and SMC did not help.

Question 1: Any suggestions?

Question 2: Any ideas where else the logic board provides 5V I could use to power the USB?

Thanks for for Your time!