1. Make sure that the voltage across the DC power source cable leads is 0 V and that
there is no chance that the cables might become active during installation.
CAUTION: You must ensure that power connections maintain the proper
polarity. The power source cables might be labeled (+) and (–) to indicate
their polarity. There is no standard color coding for DC power cables. The
color coding used by the external DC power source at your site determines
the color coding for the leads on the power cables that attach to the
terminal studs on the power supply faceplate.
2. Attach an ESD grounding strap to your bare wrist and connect the strap to one of the
ESD points on the chassis.
3. Switch the circuit breaker on the power supply faceplate to the off position (O).
4. Using both hands, slide the power supply into the chassis until you feel resistance.
5. Firmly push the power supply into the chassis until it comes to a stop. The power
supply faceplate should be flush with any adjacent power supply faceplates.
6. Tighten the captive screws on the top and bottom flanges of the power supply
faceplate to secure the power supply in the chassis.
7. Remove the clear plastic cover protecting the terminal studs on the faceplate.
8. Remove the nut and washer from the terminal studs.
9. Attach the lugs on the DC source power cables to the terminal studs, making sure the
cables are not touching or in the way of any router components:
•
Attach the positive (+) DC source power cable lug to the RETURN (return) terminal.
•
Attach the negative (–) DC source power cable lug to the –48V (input) terminal.
NOTE: For information about connecting to DC power sources, see
“M120 DC Power, Connection, and Cable Specifications” on page 97.
10. Secure the power cable lugs to the terminal studs, first with the flat washer, then with
the nut. Apply between 12 lb-in. (1.4 Nm) and 15 lb-in. (1.7 Nm) of torque to each nut
(see Figure 101 on page 251).
11. Loosen the captive screw on the cable restraint on the lower edge of the power supply
faceplate.
249Copyright © 2018, Juniper Networks, Inc.
Chapter 28: Replacing Power System Components
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