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Cisco 12006 and Cisco 12406 Router Installation and Configuration Guide
OL-11497-03
Chapter 4 Troubleshooting the Installation
Problem Solving with Subsystems
Troubleshooting the Power Subsystem
The power subsystem in the Cisco 12006 and Cisco 12406 Routers consists of the
following components:
• An AC PDU or a DC PDU
• One or two AC-DC power supplies, or one or two DC-input PEMs
• Backplane
• DC-DC converters
• MBus modules
The power modules provide DC output to the system via the backplane. DC output
from the alarm card powers the MBus modules on each card in the system. The
MBus modules, in turn, control the DC-DC converters also present on each card
in the system. The DC-DC converter takes DC power from the backplane and
converts it into +2.5, +3.3, and +5 VDC, which is distributed to the card circuitry.
Begin checking the power subsystem by looking at the power module LEDs:
• For DC-input PEMs, see the “Troubleshooting the DC-Input Power Entry
Module” section on page 4-26.
• For AC-input power supplies, see the following section.

Troubleshooting the AC-Input Power Subsystem

Begin checking the AC-input power subsystem by first looking at the LEDs on the
AC-input power supplies (see the “AC-Input Power Supply LEDs” section on
page 4-17). When you start up the system by turning on facility power to the
system, the following should occur:
• The green LED labeled AC should go on immediately. It should remain on as
long as the system is receiving satisfactory AC power levels from the facility
AC power source.
• The green LED labeled DC indicates the status of the power module DC
output power and internal DC voltages. This LED stays on when all the
following conditions are met:
–
The power supply is fully seated in its bay.
–
The power supply power standby switch is on.