Juniper QFX10016, Hardware Manual

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5. Remove the plastic cable cover from the power input terminals by using the Phillips (+) screwdriver,
number 2, to loosen the screws (see
Figure 154 on page 305 ).
Figure 154: Removing the Plastic Cable Cover on a JNP10K-PWR-DC2 Power Supply
6. Remove the nuts from each DC power input terminal, using the 13/32 in. (10 mm) nut driver or
socket wrench to loosen the nuts.
7. Ensure that the power source circuit breaker is open so that the voltage across the DC power
source cable leads is 0 V and that the cable leads do not become active while you are connecting
DC power.
8. Verify that the DC power cables are correctly labeled before making connections to the power
supply. In a typical power distribution scheme where the return is connected to chassis ground at
the battery plant, you can use a multimeter to verify the resistance of the –48V and RTN DC cables
to chassis ground:
• The cable with very high resistance (indicating an open circuit) to chassis ground is negative (–)
and will be installed on the –48V (input) DC power input terminal.
• The cable with very low resistance (indicating a closed circuit) to chassis ground is positive (+)
and will be installed on the RTN (return) DC power input terminal.
305