NEC Express5800/R120b-1 User Manual page 379

Upgrading Your Server 9-23
NOTE:
If one of the two power supply units of the server is replaced,
the AC POWER LED of the new power supply unit goes on amber until
the AC power cord is connected. It turns on green when the AC power
cord is connected. (If it is replaced while the power is off, the LED
flashes green. The LED goes on green when the power is turned on.)