Weird power issue on R720XD

Hi,

On Monday we had an R720XD shut down following a number of power errors (The system board BP1 5V PG voltage is outside of range, The system board fail-safe voltage is outside of range, PWR2402 iDRAC is unable to communicate with power managament firmware)  Following this, it would not boot up. Although the power supplies had green status indicators, I tried a known working supply which changed nothing. Today, I installed a different system board however it is still not booting, I shall describe the behaviour as follows:

Power is supplied to server, fans spin slowly then amber flashing hdd/fan led and power leds on front. Nothing out of VGA outputs and cannot access DRAC over network due to unknown IP of new board and no success in trying default IP having reset DRAC.

Please advise me as to how to continue/what the problem may be.

Many thanks in advance

James