HELP - My phone is bricked - cannot load recovery mode... ;(

Hello,

I loaded my SM-G900F with a custom rom and it suddenly died... There is no way to switch it on and when I connect it to my laptop it shows QHSUSB_BULK under device manager. I read a lot of posts and I understand that I need an unbrick image to boot from an sd card. Is that the right thing to do?

I would really appreciate is somebody could help.

Thanks in advance!
buralbe