board not powering on

[hariharan_srm]

i have connected usb type(b) to j3 and kept the switch to usb but no advertsing happens and i have also connected external supply 3v to p21 the board is not on . only while connecting usb with j2 and keeping the switch on the vdd mode board works . whetherany jumper has be connected or any solderings to be made between any things. i have also kept the nrf only to default siwtch in both ways but no board powersup. i wan to step by step procedure to connect the external supply to p21 i have connected the volateg and gnd to p21 but no boot happening

[Elfving]

Hi,

ave also kept the nrf only to default siwtch in both ways but no board powersup.

So the nRF Only switch should not be necessary here. 

This older post by a coworker explains the difference between these power settings better than I could.

On my side, if I power a nRF52840DK here with the USB on the side, and with the "nRF Power Source" switch set to "USB", I do still see advertisement, as well as seeing a faint light from the LEDs, given that you are running something on the nRF that are supposed to use these. Note that the LEDs would be more faint as the USB side connector would power set VDD to 1.8V. 

Does it work for you as soon as you switch the nRF Power source to VDD?

I've tested this on my side with the LBS sample and the nRF Connect app, could you try the same thing, just to compare?

Regards,

Elfving