User's Manual

CHAPTER 4 NDA-24300
Page 304
Issue 1
UNIT/CIRCUIT CARD REPLACEMENT PROCEDURE
6. Fuse Replacement
The system uses the fuses shown in Figure 4-28 as a protection against an overload resulting from a short cir-
cuit.
Figure 4-28 Fuses Used by System
When excessive current is applied to a PWR circuit card, the related fuse is blown. The blown fuse after a fault
can be confirmed as shown in Figure 4-29.
Figure 4-29 Blown Fault Example
The purpose of fuses is to let them blow before the components are damaged. If any fuse gets blown, replace
it immediately with a new one using the following procedure:
(1) Confirm the blown fuse via the system message [6-A] or MJ lamp on the top of IMG0.
(2) Replace the fuse with a new one, referring to Figure 4-30 and Figure 4-31.
(3) Determine the cause of the blown fault, referring to Figure 4-32 (case of RGU fuse) or Figure 4-33 (DC-
48V fuse.)
1.5A
12.5V
25A
If a fuse is blown,
this area turns white.
A normal fuse A blown fuse