Replacing an M320 DC Power Supply Cable

To replace a power cable for a DC power supply:

1. Locate a replacement power cable that meets the specifications defined in M320 DC Power Cable Specifications.

   Caution: A licensed electrician must attach a cable lug to the power cable that you supply. A cable with an incorrectly attached lug can damage the router (for example, by causing a short circuit).

2. 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 the removal process.

   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 each power supply.

3. Attach an electrostatic discharge (ESD) grounding strap to your bare wrist, and connect the strap to one of the ESD points on the chassis.
4. Switch the circuit breaker on the DC power supply faceplate to the off position (O).
5. Remove the power cable from the DC power source.
6. Remove the clear plastic cover protecting the terminal studs on the faceplate.
7. Remove the nuts and washers from the terminal studs (see Figure 1). (Use a 7/16-in. (11 mm) nut driver.)
8. Remove the cable lug from the terminal studs.
9. Loosen the captive screw on the cable restraint on the right edge of the power supply faceplate.
10. Carefully move the power cable out of the way.
11. Attach the lug on the replacement power cable to the terminal studs, making sure the cable is not touching or in the way of any router components.
12. Attach the lugs on the DC source power cables to the terminal studs.
    1. Attach the lugs on the positive (+) DC source power cables to the terminal studs.
    2. Attach the lugs on the negative (–) DC source power cables to the terminal studs.

    Secure each cable lug to the terminal stud, first with a washer, then with a nut. Use a 7/16-in. (11 mm) nut driver or socket wrench to tighten the nut. Apply between 23 lb-in. (2.6 Nm) and 25 lb-in. (2.8 Nm) of torque to each nut.

    Note: The DC power supplies in slots PEM0 and PEM1 must be powered by dedicated power feeds derived from feed A, and the DC power supplies in slots PEM2 and PEM3 must be powered by dedicated power feeds derived from feed B. This configuration provides the commonly deployed A/B feed redundancy for the system.

13. Route the power cable through the cable restraint.
14. Tighten the cable restraint captive screw to hold the power cable in place.
15. Replace the clear plastic cover over the terminal studs on the faceplate.
16. Attach the power cable to the DC power source.
17. Verify that the DC source power cabling and grounding cabling are correct, that they are not touching or blocking access to router components, and that they do not drape where people could trip on them.
18. Switch the circuit breaker on the DC power supply faceplate to the on position (|). Verify that the OUTPUT OK status LED on the power supply faceplate blinks, then lights steadily approximately 1 minute after you switch the power supply circuit breaker on.

Figure 1: Disconnecting or Connecting a Power Cable from a DC Power Supply