Juniper MX480 Hardware Manual page 443

If a DC power supply is correctly installed and functioning normally, the PWR_OK, INPUT OK, and
BREAKER ON LED's light steadily.
Issue the CLI show chassis environment pem command to check the status of installed power supply
modules. As shown in the sample output, the value Online in the rows labeled State indicates that each
power supply is functioning normally:
user@host> show chassis environment pem
PEM 0 status:
State
Temperature
DC output
PEM 1 status:
State
Temperature
DC output
If a power supply is not functioning normally, perform the following steps to diagnose and correct the
problem:
If a red alarm condition occurs, issue the show chassis alarms command to determine the source of the
problem.
Check that the AC input switch (—) or DC circuit breaker (|) is in the on position and that the power
supply is receiving power.
Verify that the source circuit breaker has the proper current rating. Each power supply must be connected
to a separate source circuit breaker.
Verify that the AC power cord or DC power cables from the power source to the router are not damaged.
If the insulation is cracked or broken, immediately replace the cord or cable.
Connect the power supply to a different power source with a new power cord or power cables. If the
power supply status LEDs indicate that the power supply is not operating normally, the power supply
is the source of the problem. Replace the power supply with a spare.
If all power supplies have failed, the system temperature might have exceeded the threshold, causing
the system to shut down.
NOTE: If the system temperature exceeds the threshold, the Junos OS shuts down all power
supplies so that no status is displayed.
The Junos OS also can shut down one of the power supplies for other reasons. In this case,
the remaining power supplies provide power to the router, and you can still view the system
status through the CLI or display.
Online
OK
OK
Online
OK
OK
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