Recently R640 stopped booting, can access iDRAC but not showing any error or a relevant log. Once plugged in, both the power supplies are green, but not getting any response to the power on button. 

Fans briefly spin for 30 seconds slowly once plugged in and then stop.  Nothing shows on the screen connected to the VGA port. Drained flea power, cleared NVRAM and tried booting with minimum config, but no luck

Any suggestions?