Cisco 12008, Installation And Configuration Manual, Page: 258 / 382

Troubleshooting Overview
Cisco 12008 Gigabit Switch Router Installation and Configuration Guide 5-8
If this LED does not go on, or if it goes off while system power is still applied, there
could be a problem with either the source power itself or the DC output voltages being
delivered to the backplane (+5 VDC and –48 VDC). There could also just be a problem
with the MBus controller inside the power supply.
The AC INPUT OK LED (AC-input power supply) or the INPUT OK LED (DC-input
power supply) stays on when all of the following conditions are satisfied:
— The power supplies are on and receiving normal source power.
The source power specifications for the AC-input power supply are 180 VAC to
264 VDC, 50 to 60 Hz, single phase.
The source power specifications for the DC-input power supply are –40.5 VDC to
–70 VDC.
— The power supplies are providing the n5.2 VDC and –48 VDC operating
voltages to the backplane.
If the AC or DC source power or the DC operating voltages being supplied to the
backplane fall outside the allowable tolerances, the OUTPUT FAIL LED on the power
supply goes on, because a problem with either of the DC operating voltages being
supplied to the backplane prevents the system from starting up or continuing normal
operations.
For example, if a problem occurs with the –48 VDC line that supplies power to the
router’s internal components (see Figure 1-23), the system fails during the boot
sequence.
Depending on when the OUTPUT FAIL LED goes on, proceed as follows:
— If the AC INPUT OK LED (AC-input power supply) or the INPUT OK LED (DC-
input power supply) stays off when system power is applied, there is a problem with
either the AC or the DC source power or the connection to the power supply. In this
case proceed to the section entitled “Troubleshooting the Power Subsystem.”
— If the AC INPUT OK LED (AC-input power supply) or the INPUT OK LED (DC-
input power supply) goes on temporarily and then goes off within 30 seconds, the
system is probably shutting itself down because it detected an out-of-tolerance
power or temperature condition within a power supply. In this case proceed to the
section entitled “Troubleshooting the Power Subsystem.”