Precision 7920 Boot Problem

Hi All,

I purchased a used 7920 to replace my current rig (7910) to move on to Windows 11. After getting the machine I put a 4xnvme card in it, installed Win11 and ran DCU to update everything which included a BIOS update. I let it go overnight and shut it down next day without checking the results (it was on the dinning room table and breakfast was being server)! It no longer boots up. Well it turns on but nothing happens, white power light but nothing else. I thought it might be a bad BIOS burn but it doesn't do the BIOS recovery 2, nothing happens when I press CTRL+ESC on power on. I replaced the button battery, still no good. I'm in the process of removing components to see which is being problematic. I removed all the memory sticks and it flashed no memory lights (2amber, 3white or vice versa) so I'm thinking the BIOS is not too coruptted!!! 

Any ideas on how to proceed before I tear it down all the way? 

TIA,