This article provides information on how to set the dip switch, which is found on the back of the high capacity AC/DC PEMs being used in MX960 routers.

Incorrect setting of this DIP switch will raise alarms in the chassis.

For more information, refer to the following link:

www.juniper.net/techpubs/en_US/release-independent/junos/topics/task/installation/power-supply-mx960-high-capacity-ac-connecting.html

Each High Capacity AC/DC PEM will accept two AC/DC feeds in two unique AC/DC receptacles. It is possible to operate with one feed as well, but with lower power output from that PEM. This DIP switch should be set according to the number of AC/DC feeds that are present for the PEM.

• Position – 0 indicates that only one AC/DC feed is provided.
  
• Position – 1 indicates that two AC/DC feeds are provided.

The same can be verified by issuing the show chassis power command. In this example, PEM 0 has the DIP switch set to Position 1 , as two AC feeds are present. PEM 1 has the DIP switch set to Position 0 , as only one AC feed is present. Also, notice the reduction in the capacity of the PEM, when any one of the AC feeds is removed:

# run show chassis power
PEM 0:
State: Online
AC input: OK (2 feed expected, 2 feed connected) Capacity: 4100 W (maximum 4100 W)
DC output: 855 W (zone 0, 15 A at 57 V, 20% of capacity)

PEM 1:
State: Online
AC input: OK (1 feed expected, 1 feed connected) Capacity: 1700 W (maximum 4100 W)
DC output: 969 W (zone 1, 17 A at 57 V, 57% of capacity)

For more information on the DIP Switch position, corresponding PEM LEDs, and power capacity, refer to the following links:

• www.juniper.net/techpubs/en_US/release-independent/junos/topics/task/installation/power-supply-mx960-high-capacity-dc-connecting.html
  
• www.juniper.net/techpubs/en_US/release-independent/junos/topics/task/installation/power-supply-mx960-high-capacity-ac-connecting.html
  
• http://www.juniper.net/techpubs/en_US/junos/topics/reference/command-summary/show-chassis-power.html

> show chassis alarms
4 alarms currently active
Alarm time Class Description
2013-01-11 14:48:26 UTC Minor PEM 0 Dipswitch 0 Feed Connection 2

And when the show chassis power command is issued, the PEM in question should have the following output:

PEM 0:
State: Online
AC input: OK ( 1 feed expected, 2 feed connected ) Capacity: 4100 W (maximum 4100 W)
DC output: 855 W (zone 0, 15 A at 57 V, 20% of capacity)

When you see the above output, check the dip switch. If it is in the wrong position, flip it to the correct one and this should clear the alarm.

NOTE: Flipping the dip switch will not impact traffic. However, it is always recommended to do so in a maintenance window to guard against unforseen circumstances.

• show chassis power