I have a solid PSU putting out 5.4VDC capable of 60amps/300watts. I have 5.4VDC going into the Pi3, but get the lightning bolt/undervoltage condition. On Pins 2 & 6 on the GPIO I'm only getting ~4.5/4.6 VDC. I am measuring with a Fluke 289, not some $5 meter. Is there some diode between the USB port and the GPIO causing the voltage drop? (I'm going to make a cable to rule that out.)
Edit: Yup was cable. (I hate making cables). Anyone got a line on micro USB power only cables with a heavier gauge? Say 22 or 24? Right angle would be killer.