Northern Telecom BCS35 Replacement Manual page 174

158 Power supplies
Procedure 17–1
Power supply replacement
Step Description
1 Remove the front panel of the DPP. Put it
in a safe place to avoid damage. Remove
only the top panel if you are changing the A
power supply.
Remove both the A and B front panels if
changing the B power supply.
2 Make sure the other CPU is in the ONLY
mode of operation, and the other disk is in
the ONLY mode of operation. First put the
disks to an ONLY mode.
3 Power down the faulty power supply. See
Figure 17–1.
Remove the –48 V dc C.O. power.
4 Remove the three connector plugs from the
front of the power supply.
5 Loosen the slotted–head captive screw at
the bottom of the power supply.
6 Gently pull the power supply out of the
chassis.
7 To install the replacement power supply,
make sure all cables and connectors are
out of the way of the insertion path.
8 Gently slide the power supply into position
until it is fully seated.
297-1001-536 Standard 01.03 August 1996
Notes
Loosen the four captive screws on the
left and right sides of the front panel;
carefully remove the front panel.
This allows access to the Switch and
Status Panel.
Press the A/B rocker switch to match
the processor with the good power
supply. Press the O/P switch to 0 and
turn the key switch 45
Remove the –48 V dc source for the
processor chassis at the DMS–100 fuse
panel; disk drive in this chassis is now
disabled
Pull down gently; fold the cables back
out of the way.
Make sure the three connectors (and
cables) are out of the way during
removal of the power supply unit.
Make sure the proper fuses are installed
in the replacement power supply. See
Table 17–1 and Figure 17–1.
If any resistance, remove the power
supply and check for obstructions.
Remove the obstructions and reinsert
the power supply.
(continued)
∂
clockwise.