Service manual

GS80 Component Removal and Replacement 6-33
Removal
1. Open the front door.
2. Locate the power supply that needs to be replaced:
1. Associate a power subrack with the drawer with the power problem; the
upper drawer is powered by the upper subrack, the lower drawer by the
lower subrack. At least one of the power supplies on the identified
subrack should be replaced.
2. If the drawer 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 drawer 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 1.23.3. 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.