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Cisco MGX 8950 Hardware Installation Guide
Release 3, Part Number 78-14147-02 Rev. A0, November 2002
Chapter 4 Maintaining the Cisco MGX 8950 Switch
Swap a Primary or Redundant DC PEM with Power On
Step 1 Connect a grounding strap to the ESD grounding jack or to the equipment rack.
Step 2 Turn off the circuit breaker only on the DC PEM that you intend to replace.
Step 3 Turn off the branch circuit at the DC source (the distribution box, for example) for the correct branch.
Step 4 If your terminal block has a plastic cover, complete the following steps to disconnect the DC source
wiring:
a. Use a Phillips-head screwdriver to remove the plastic terminal block cover on the DC PEM that you
intend to replace (see
Figure 4-1).
Figure 4-1 DC PEM Faceplate
b. Disconnect DC source wires at the wiring terminal blocks on the DC PEM.
Step 5 If your terminal block does not have a plastic cover, complete the following steps to disconnect the DC
source wiring:
Caution The cable connector must be disconnected at the backplane first, when inserting or removing the PEM
with power on. If you disconnect the cable at the PEM first when power is on, the cable contacts will be
energized. If the energized cable contacts touch the surface of the chassis or any metal connected to the
chassis, the –48 VDC will be shorted to the chassis, and the circuit breaker on the still-active PEM will
open, shutting down the system.
a. Locate the backplane end of the system power cable for the DC PEM that you intend to replace.
b. At the backplane end of the system power cable, loosen the captive screws on the cable bracket.
c. Pull the cable bracket out approximately one inch to disconnect the cable.
1 Two-position circuit breaker. The positions
are Off and On.
4 Plastic cover.
2 J1 output connector. 5 Terminal block 1 (DC input).
3 LED showing status of the DC PEM.
J1
-48V
OFF
ON
RTN
DC OK
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