Cisco Catalyst 9404R Switch Hardware Installation Manual page 101

Removing and Replacing FRUs
Removing the Power Supply
Caution Do not leave any power supply slot open for any amount of time while the system is powered up.
Prior to inserting a new power supply unit, for instance, when replacing the unit, ensure there are
no foreign, conductive or other objects, or debris in the slot.
Cisco Catalyst 9400 Series Switches Hardware Installation Guide
95