Replace TPA and GMT Fuses in the PDU

For information about the Power Distribution Unit (PDU), refer to Power Management.

The following fuse types are included with your system:

• two TPA fuses for each shelf, one for A feed and one for B feed and a spare (48V, 40A rated  fuse, Ribbon Part Number 160Q003110)
• three GMT fuses for alarm panel (0.75A, 60VDC per each fuse, Ribbon Part Number  160Q003210)

Each TPA fuse location in the PDU has an individual fuse alarm LED (red) that is lit if there is a problem with the respective load (or the fuse itself). However, the GMT fuses have only one fuse alarm LED (red) that is lit. You can identify which of the GMT fuses need to be replaced by examining each GMT fuse. The indicator on the failed fuse springs forward and should be visible on the bottom side of the fuse.

The following figure is an illustration of a typical GMT fuse.

GMT Fuse

The TPA module comprises a fuse and holder and is intended to create a power disconnect condition to the equipment to which it is connected downstream. This module creates the power disconnect by burning out in the event of an over-current condition in the downstream equipment. The fuse is only to be replaced with the power to the unit turned off and the fault condition cleared and it is not to be used as the on and off switch for the equipment to which it is connected downstream. Reconnecting a TPA module with the PDU under power with an enabled load may damage the TPA module. It is recommended that the load devices (power supplies) are switched off (or removed) before replacing a TPA fuse.

Mapping of TPA Fuses to Power Modules

The following figure shows the mapping of TPA fuses to the DSC Platform power modules in each shelf.  For information about removing a power module, refer to Replace a Faulty Power Module (PM) .

Mapping of TPA Fuses to Power Modules

The following figure shows the power module locations.

Power Module Locations

Replace TPA Fuses

Start

1. Obtain the fuse of the recommended size. 

   Tip

   The current rating of the fuse (in Amps) is indicated on the fuse.

            

2. Unseat all Power Modules (PMs) in the shelf as required (see the preceding figures).
3. Extract the fuse holder from the PDU by pulling this holder outward until it is completely removed from the PDU.
4. Remove the TPA fuse by gently prying it out with a small flat-head screwdriver, or pulling it out with small needle nose plier.
5. Use a small screwdriver to push the plastic spring slip aside while pulling on the wire/terminal from the back of the connector.

6. Insert the new fuse into the fuse holder, as shown in the following figure.
   Fuse Holder

   

7. Insert the fuse holder with the new TPA fuse into the PDU.

   Tip

   Press firmly on the fuse holder to make sure that it is properly seated.

                       

8. Verify that the fuse alarm LED on the front of the fuse holder is off.

9. Reinsert the power supply in the shelf and use a multimeter, as required, to verify that the output voltage of the equipment is a nominal -48 VDC and the polarity of the negative and  positive wires is correct.

Replace GMT Fuses

Start

1. Obtain the fuse of the recommended size.

   Tip

   The current rating of the fuse (in Amps) is indicated on the fuse. The color of the indicator also corresponds to the fuse size. Use the color code chart provided with the fuse to confirm that you are using the appropriate fuse.

                  

2. Using a fuse puller as shown in the following figure, remove the faulty fuse from the PDU.

   Tip

   It is recommended that you use a fuse puller to extract a GMT fuse: otherwise, you may break the fuse in its slot.

   Fuse Puller

   
3. Orient the fuse so that the indicator is on the bottom.

4. Insert the new fuse into the appropriate fuse slot.

   Tip

    The fuse alarm indicator on the PDU faceplate should be off.