Strange beahviour or not

Hi, I purchased a Arduino Ethernet All-In-One with POE module and USB to serial adapter.
I connected it to PC USB - and power supplied from USB itself, I suppose.
PS I'm yet fighting with programming and serial port issues)
At power-on, Power LED are both on (Serial adapter and main board).
L9 LED on main board is sometimes on, some OFF, some other times it ripples at 50hz frequency. Behaviour changes if I move the board, or wave my hands in front of it.
Is it the normal behaviour of the board?
Thanks for reply!!!!

L9 LED on main board is sometimes on, some OFF, some other times it ripples at 50hz frequency. Behaviour changes if I move the board, or wave my hands in front of it.

Can you see an LED flashing at 50Hz, I think not.

It sounds like you have a floating input if hand movement changes what it does. This means you are missing something in the way you wire it up.

Thanks for fast reply.
I didn't wire anything, should I?
I just plugged in the USB mini adapter on the Serial2USB module....!

I make the question with different words... What is the state of th L9 led in a brand new Arduino Ethernet after pressing reset?

Resolved... I managed to program board with "blink" sketch (from another PC...) and - when programmed as output - the Pin is in stable condition.
Now I've to resolve the jam with my primary PC not working on Arduino port, but this is another thread!. :slight_smile: