If none of the CPUs are working with CPU socket 2, I'd be looking at the motherboard as a potential failure. If the old CPUs continue to work with CPU socket 2, you could test the new CPUs on a different motherboard.  Updating the BIOS and iDRAC shouldn't impact the PSU at all, but you can perform a power drain, just to be safe. This would be done by shutting the server down, unplugging it, then holding the power button down for 30 seconds. You can then bring it back up as normal.
Hi to all, I have bought 2 new CPU (E5-2660 v2) for my R620 with 2x E5-2603). After the change of the CPUs the server recognize only 1, the CPU1 and not the CPU2. I have passed all the day to updgrade BIOS and Idrac firmware (1 by 1 from the oldest to the newest) but always the same problem. The server start, the fan start at max speed and remain in this state, esxi 5.5 start but before the final screen the system reboot.   Thanks for the help  
R620 problem with new CPU