Replacing an M120 AC Power Supply

In the AC power configuration, the router has two AC power supplies (see AC Power Supply), located at the rear of the chassis in slots PEM0 and PEM1 (left to right). Each AC power supply provides power to all components in the router. The AC power supplies are fully redundant and current is shared almost equally in a fully configured system. In a fully configured router, if one power supply fails or is removed, the remaining power supply instantly assumes the entire electrical load.

Each power supply (AC or DC) is hot-insertable and hot-removable.

Note: To maintain proper cooling and prevent thermal shutdown of the operating power supply unit, each power supply slot must contain either a power supply or a blank panel. If you remove a power supply, you must install a replacement power supply or a blank panel shortly after the removal.

Removing an M120 AC Power Supply

The power supplies are located at the rear of the chassis to the right of the CB1. Each power supply weighs approximately 8.4 lb (3.8 kg).

Caution: Do not leave a power supply slot empty for more than 30 minutes while the router is operational. For proper airflow, the power supply must remain in the chassis, or a blank panel must be used in an empty slot.

Note: After powering off a power supply, wait at least 60 seconds before turning it back on.

To remove an AC power supply (see Figure 1):

1. Attach an electrostatic discharge (ESD) grounding strap to your bare wrist, and connect the strap to one of the ESD points on the chassis.
2. Move the power switch on the power supply faceplate to the standby position.
3. Unplug the power cords from the power source receptacles.
4. Remove the cable restraint from the lower edge of the power supply faceplate by removing its retainer screw.
5. Unplug the power cord from the appliance inlet on the power supply faceplate.
6. Loosen the captive screw on each flange at the top and bottom of the power supply faceplate completely.
7. Grasp the handle on the power supply faceplate and pull firmly. Slide it halfway out of the chassis.
8. Place one hand underneath the power supply to support it and slide it completely out of the chassis.

   Warning: Do not touch the power connectors on the rear of the power supply (see Figure 2). They can contain dangerous voltages.

Figure 1: Removing an M120 AC Power Supply

Figure 2: Rear of the M120 Power Supply Showing Midplane Connector

Installing an M120 AC Power Supply

To install an AC power supply (see Figure 3):

1. Attach an electrostatic discharge (ESD) grounding strap to your bare wrist, and connect the strap to one of the ESD points on the chassis.
2. Move the power switch on the power supply faceplate to the standby position.
3. Using both hands, slide the power supply into the chassis until you feel resistance.
4. 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.
5. Tighten the captive screws on the top and bottom flanges of the power supply faceplate to secure the power supply in the chassis.
6. Insert the appliance coupler end of each power cord into the appliance inlet on the power supply faceplate.
7. Remove the cable restraint from the lower edge of the power supply faceplate by removing its retainer screw.
8. Wrap the cable restraint around the power cord, then slide it along the power cord to a position that enables you to reinstall it in the power supply faceplate.
9. Reinstall the cable restraint by tightening its retainer screw part of the way into the power supply faceplate.
10. Carefully pull the AC power cords through the cable restraint until you have the desired amount of slack in the power cord.
11. Tighten the cable restraint retainer screw to hold the power cords in place.
12. Insert the power cord plugs into an AC power source receptacle. Verify that the power cord does not block access to router components or drape where people could trip on it.

    Note: Each AC power supply has two AC appliance inlets. Each power supply must be connected to a dedicated AC power feed. For 100-120 VAC, both inlets are used. For 200-240 VAC, only the top inlet is used. For information about site power preparations, see M120 Router Power Requirements. For information about connecting the router to power and ground, see Connecting Power to an AC-Powered M120 Router.

13. 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.

Figure 3: Installing an M120 AC Power Supply