Maintaining Power Supplies

To verify that the power system is functioning normally, perform the following procedures regularly:

• Check the LEDs on the faceplate of both power supplies. A power supply is functioning correctly when the green LED labeled CB ON is lit steadily (indicating that the circuit breaker is switched on) and the blue LED labeled OUTPUT OK is lit steadily (indicating that the supply is receiving power from the DC source).

  If these LEDs are blinking or other LEDs are lit, there could be an error condition. For a summary of LED states, see Power Supply.

• Issue the following CLI command to check the status of the power supplies. The following example specifies a slot number (0), which is optional. As shown in the sample output, the value Online in the State column indicates that the power supply is operating normally:
  user@host> show chassis environment pem 0

  PEM 0 status:
    State                           Online
    Temperature                     OK
    DC input                        OK
    DC Output                       OK
    Load                            Less than 40 percent
    Voltage:
      48.0 V input            55059 mV
      48.0 V fan supply       50181 mV
      5.0 V bias               5032 mV
      8.0 V bias               8224 mV
   

  The messages in the craft interface LCD and the output from CLI show commands refer to the power supply on the right as PEM 0 and the power supply on the left as PEM 1.

  For further description of the output from the command, see the JUNOS Internet Software Operational Mode Command Reference: Protocols, Class of Service, Chassis, and Management.

• Check the red and yellow alarm LEDs and the LCD on the craft interface. Power supply failure or removal triggers an alarm that causes one or both of the LEDs to light and an error message to appear on the LCD. You can display the associated error messages by issuing the following CLI command:
  user@host> show chassis alarms

  For a list of possible alarm messages, see Chassis and Interface Alarm Messages.

• Verify that the power source has the proper current rating and that each power supply is connected to a separate power source.
• Verify that the cable or cord connecting the power supply to the external power source is securely in place and that there is no moisture accumulating near the router.
• Verify that the cable or cord from the power source to the router is not damaged. If the insulation is cracked or broken, replace the cable or cord immediately.
• Verify that the power cables or cord do not touch or obstruct access to other router components, and that they do not drape where people could trip on them.
• Verify that the air flow in and out of cooling system components is not obstructed.