Hello Nestico27, I would say you are correct that your motherboard is needing to be replaced since you are not able to get to the bios & the system doesn’t complete post. Please let us know if you have any other questions.
Hello, I know this thing is VERY old, but I have a PowerVault 725N I use for IP camera storage, recently it will POST but hangs just after POST saying "System Health OK!" in the event that it does pass this screen it hangs at a black screen where it should be displaying the screen just before the boot cycle where it displays device info and such. I'm lost on what could be wrong, clearing CMOS does not help even to the slightest. Before I go and spend $20 on a new board for it, I was wondering if I can get it to work as is.    A little extra info, all 4 drives work as they did before the system started doing this, it does it regardless if drives are present. I have tried different RAM and CPU's aswell as a power supply. I have attached a photo for reference.   [IMAGE]  
PowerVault 725n