UNIT/CIRCUIT CARD REPLACEMENT PROCEDURE

6.Fuse Replacement

The system uses the fuses shown in Figure 4-28as a protection against an overload resulting from a short cir- cuit.

1.5A

25A

12.5V

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.

If a fuse is blown, this area turns white.

A normal fuse

A blown fuse

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 4-30and 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.)

CHAPTER 4

NDA-24300

Page 304

Issue 1

Page 331
Image 331
NEC NDA-24300 manual Fuse Replacement, Fuses Used by System