Manual

Chapter 4 Troubleshooting the Installation
Troubleshooting an AC Power Subsystem
4-6
Cisco XR 12404 Router Installation Guide
OL-13830-02
Troubleshooting an AC Power Subsystem
AC PEMs provide –48 VDC OUTPUT. The +5 VDC OUTPUT from the CSF
powers the MBus module on each card in the system. The MBus module, in turn,
control the DC-DC converters also present on each card in the system. The
DC-DC converter takes –48 VDC from the power supply and converts it into +2.5,
+3.3 and +5 VDC, which is distributed to the card circuitry.
AC PEMs are monitored by the MBus module and the RP for over- or
u
ndervoltage and over- or undercurrent conditions.
Begin checking the power subsystem by first looking at the LEDs on the power
supply
. The INPUT OK LED on an AC PEM lights when AC power is applied;
t
he OUTPUT OK LED lights when the PEM power switch is turned on.
Figure 4-1 sho
ws the location of the LEDs on the AC PEM (item 5).
Figure 4-1 AC PEM
1 AC PEM handle 4 Power cord receptacle
2 On/Off switch 5 LEDs
3 Bail Latch 6 Captive screws
INPUT
OK
OUTPUT
FAIL
INPUT
100-240V
12A
50/80HZ
OUTPUT
OK
66289
456
1
2 3
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