Troubleshooting The Dc Power Subsystem - Cisco 12404 Installation And Configuration Manual

Troubleshooting the Power Subsystem

Troubleshooting the DC Power Subsystem

Cisco 12404 Internet Router Installation and Configuration Guide
4-20
The DC PEMs and PDUs provide DC power to the router which is distributed to
the card circuitry.
Begin checking the power subsystem by first looking at the three LEDs on the
power supply faceplate. The INPUT OK LED on an DC PEM goes on when DC
power is applied, The OUTPUT OK LED goes on when the PEM power switch is
turned on.
The amber OUTPUT FAIL LED is normally off, but goes On if the PEM detects
a fault.
The DC PEMs are monitored by the MBus module and the RP for over- or
undervoltage and over- or undercurrent conditions.
Continue by checking the following to help isolate the problem with the power
subsystem.
Are the power supply INPUT OK and OUTPUT OK LEDs on?
•
If yes, the power source is good, and the power supplies are functional.
–
If no, but the fan tray assembly is operating, suspect a faulty PEM LED.
–
If the fan tray assembly is operating, all internal DC voltages are within
tolerance. Use the show environment command to check the voltages on
each card. The fan tray assembly uses –48 VDC.
If no and there is not other obvious activity, first suspect that the PEM,
–
power switch is not in the ON position. Ensure the PEM power switch is
On.
If the PEM power switch is On and the INPUT OK LED remains off,
–
suspect the DC power source, or the power cable.
Turn the PEM power switch Off and check the DC power source at the
•
DC PDU terminal block.
Verify that the DC power source circuit breaker is On and has not tripped.
•
Verify that the DC power source circuit breaker has the proper current rating.
•
Verify each DC PEM in the Cisco 12404 router chassis is attached to a
•
separate power source.
Check that the uninterruptable power supply (UPS) is functioning correctly.
•
Systems powered by a DC power source, might have a UPS for each DC PDU
in the system.
Chapter 4 Troubleshooting the Installation
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