Seeeduino Mega V1.1 ext pwr problem

I have the Seeeduino Mega V1.1 and when trying to run it on +5V ext. power board resets.

Vcc at JST connector is +5V
Vcc at U6 is +4,3V
Vout of U6 is 3,3V !!!

Reading text on U6 is: 1117-5

System will power up when Vcc at JST measures 8,54V
Vcc at U6 is 7,51V
Vout of U6 4,99V

Switching to USB power and board works again…

Not the greatest thing when this board is going to africa for datalogging soon…

It says in the specifications the minimum input voltage is 6v. It works for me with 5.6V going in through the Vin pin, although the regulator output is only 4.4V in this case. If you still want to use the JST input you could short out the diode D1 next to the JST, at the expense of losing reverse-voltage protection.