Help us improve your experience.

Let us know what you think.

Do you have time for a two-minute survey?


Replacing an M120 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 M120 DC Power, Connection, and 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 the power supply faceplate.

  3. Attach an 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 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 nut and washer from the terminal studs (see Disconnecting Power Cables from the DC Power Supply). (Use a 3/8–in. nut driver or pliers.)
  8. Remove the cable lug from the terminal studs.
  9. Loosen the captive screw on the cable restraint on the lower 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. 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 Connecting Power Cables to the DC Power Supply
  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 is correct, that the cables are not touching or blocking access to router components, and that they do not drape where people could trip on them.
  18. Switch the power switch on the power supply faceplate to the on position (|). Verify that the status LED on the power supply faceplate blinks, then lights steadily approximately one minute after you switch on the power switch.