Hi i just install a new relay with a rb600. On it i put one XR5 , one XR2 and a XR9. I used a industrial 48V 2AMP Power supply not on pppoe because i got some problem on pppoe. But the guy who responsible to install the stuff on the tower told me that the board make a strange noise... So i dont know what can cause this or is a sign of something goes wrong. Its not reboot. the 5ghz and 2.4 look like running fine. I have some trouble with the 900 mhz band but is my first try of use this band. And is my first rb600. I ever used rb532 in my other installation and i never get this kind of problem.