Service manual

Power Cabinet Component Removal and Replacement 5-31
Removal
1. Open the front door of the power cabinet.
2. Locate the power supply that needs to be replaced:
1. Use the color codes to associate a power subrack with the QBB with the
power problem. At least one of the power supplies on this subrack
should be replaced.
2. If the system box has redundant power, the associated subrack will have
three power supplies. The power supply with its 48V LED off is the one
to replace. (The failed supply may have both the 48V LED and the Vaux
LED off.)
3. If, on the other hand, the system box does not have redundant power,
the subrack will have two power supplies and both will have the 48V
LED off. If one of the two also has its Vaux LED off, it is the power
supply to replace. But if both have their Vaux LEDs lit, do the
following:
1. At the Pnn>>> prompt use the reset command to power on the
failing QBB. (A power supply can power up a QBB but not run it.)
2. The power supply with its 48V LED off is the supply to replace.
3. Loosen the two captive screws
that hold the target power supply in place.
4. Grasp the power supply handle
and firmly pull it from the subrack.
Replacement
If the power supplies are not properly load/phase balanced, the circuit breakers
will trip. To avoid this nuisance, return power supplies to the location from
which they came. See Section 1.22.3. Reverse the steps outlined in the removal
procedure.
Verification
Power on the system and make sure the LEDs on the new power supply come
on.