This article gathers documentation related to power supply replacement for the appliances that belong to S-Series (except for S200 since it only has one PSU).
S400 Series Power Supply Unit replacement:
https://techdocs.broadcom.com/content/broadcom/techdocs/us/en/symantec-security-software/web-and-network-security/hardware-appliances/1-0/S-Series-WebGuide/S400_Welcome/S400_FRUs/S400_PSUs_AC.html
S500 Series Power Supply Unit replacement:
https://techdocs.broadcom.com/content/broadcom/techdocs/us/en/symantec-security-software/web-and-network-security/hardware-appliances/1-0/S-Series-WebGuide/S500_Welcome/S500_FRUs/S500_PSUs_AC.html