AT&T System 25 - Manual (Page 246)

MAINTENANCE
Power Supply Replacement
To replace the power supply, follow these steps:
Danger: Hazardous voltages are present on some backplane
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pins. Unplug power cord from the outlet, and wait at
least 5 minutes before removing rear cover or power
supply.
Remove the front cover of the cabinet.
Remove the four No. 6-32 screws at the corners of the fan
assembly.
Unplug the fan assembly from system power by removing the two
modular plugs on the left side of the assembly.
Set the fan assembly aside in a safe place.
Unplug the 3-prong ac power connector that supplies building power
to the power supply. This connector is located at the bottom front of
the power supply.
Reach into the cabinet, between the power supply and the port
carrier. At the rear of this narrow space is the multipin dc power
connector that connects the power supply to the backplane.
Remove this connector by squeezing the tabs on the top and bottom
of the plug and pulling the plug up and away from its receptacle.
Remove the four No. 10-24 screws on the left side of the cabinet
(viewed from the front). These screws secure the power supply in
position.
Pull up on the top lip of the power supply and carefully slide it out of
the cabinet. The power supply rests on the cabinet floor. There are
no additional anchors or guides. The power supply weighs about 4
pounds.
To reinstall a new power supply, follow the preceding steps in
reverse order.
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