DellPoweredge 2900 Tower Hard Drive Bays 4-7 Not online

Hi all,

Ive worked with these servers for ages and this one is throwing me right out.. Its the tower model, in its factory default configuration and specification... 

Perc 5/i RAID Card installed..

Drives 0-3 working fine,

Drives 4-7 not online, No LEDS, nothing.

Ive checked everything and have noticed that, there is a 6 pin mains plus thats not plugged into anything. Ideally I want all drives working as I want to use it for my home design and development server but, can't seem to get these online. Have checked the cabling, the Raid card, and nothing.Ive also ran, different sized SAS drives and they are recognised fine...    

Am I missing something here?  Do you need to enable these in the BIOS or configuration somewhere?  Is it the RAID card not being able to support more than 4 drives?  

Its properly doing my head in!!!!