at first I thought it was due to the PDB not being properly connected.
now with the proper 12v rails connected i still get the same ticking noise
i put my ears as close as possible and waited for the noise and 1 of them seems to be coming from the ethernet port (with the PCB)
i cant be sure as the whole aluminum case echoes the noise so cant really tell where the noise is coming from.
edit: now i know where the ticking noise is from. the damn fan and maybe the ethernet port's pcb?
i placed my phone's sound meter near the ethernet port for as long as i could (side panel open) and it registered some spike in noise.
but for the fan, my phone couldnt register the ticking noise on the meter despite hearing the ticking noise so i decided to use the vibration meter and placed it on the fan.
lucky for me, the fan gave 3 ticking noises soon after and registered nicely on the meter and my hands too (felt it through the phone)
yes there are apps for everything these days