Removing and Replacing a PSU
172 7750 SR-a4 and SR-a8 Installation Guide
Removing and Replacing a PSU
This section includes information about:
• Warnings and Notes on page 172
• Removing an AC PSU on page 173
• Replacing an AC PSU on page 175
• Removing a –48 VDC PSU on page 178
• Replacing a –48 VDC PSU on page 181
Warnings and Notes
Danger: 
• Make the ground connections first.
• Only trained and qualified personnel should install or replace this equipment and 
connect the power cables.
• External power must be disconnected at the power source. Disconnect and unplug the 
power cables before you remove and replace a PSU module.
• You must use power cables that meet local electrical code requirements.
Warning: 
• Do not install equipment that appears to be damaged.
• Impedance panels are required in all empty slots to prevent excess dust accumulation 
and to help control airflow and electromagnetic interference. Impedance panels do not 
have board components or connector pins. 
• Electrostatic discharge (ESD) damage can occur if components are mishandled. 
Always wear an ESD-preventive wrist or ankle strap and always connect an ESD strap 
to the grounding plug on the front of the chassis.