Replacing A T640 Three-Input 240-A Dc Power Supply; Removing A T640 Three-Input 240-A Dc Power Supply - Juniper T640 Hardware Manual

T640 Core Router Hardware Guide

Replacing a T640 Three-Input 240-A DC Power Supply

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The T640 router has either one nonredundant power supply or two redundant,
load-sharing power supplies. Each redundant power supply is hot-insertable and
hot-removable. When a redundant power supply is powered down or removed, the other
power supply automatically assumes the entire electrical load for the router. If you have
only one power supply, you must power off the system before removing the power supply.
Removing a T640 Three-Input 240-A DC Power Supply on page 314
1.
Setting the Input Mode Switch on a Three-Input 240-A DC Power Supply for a T640
2.
Router on page 316
Installing a T640 Three-Input 240-A DC Power Supply on page 317
3.
Replacing the T640 Cable Restraint on a Three-Input 240-A DC Power
4.
Supply on page 318
Connecting DC Power to a Three-Input 240-A DC Power Supply in a T640
5.
Router on page 320
Powering On a T640 Replacement Three-Input 240-A DC Power Supply on page 322
6.

Removing a T640 Three-Input 240-A DC Power Supply

To remove a three-input 240-A DC power supply:
Switch off the external circuit breakers to the power supply being removed. Make sure
1.
that the voltage across the DC power source cable leads is 0 V and that there is no
chance that the cables might become active during the removal process.
Attach an electrostatic discharge (ESD) grounding strap to your bare wrist, and connect
2.
the strap to one of the ESD points on the chassis.
Switch the circuit breakers on the power supply faceplate to the off position (
3.
NOTE: After powering off a power supply, wait at least 60 seconds before
turning it back on.
Remove the clear plastic cover protecting the terminal studs on the faceplate.
4.
Using a 7/16-in. (11 mm) nut driver or wrench, remove the nuts and washers from the
5.
terminal studs (see Figure 179 on page
CAUTION: You must ensure that power connections maintain the proper
polarity. The power source cables might be labeled
their polarity. There is no standard color coding for DC power cables. The
color coding used by the external DC power source at your site determines
the color coding for the leads on the power cables that attach to the
terminal studs on each power supply.
315).
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