Fault Message:

TRU 1 FAILED/TRU 1 FEEDER/WRG FAIL

Fault Code:

2460461DCP

Associated CAS:

ELEC SYS FAULT
(Advisory)

DC Power Center (DCPC) has detected a Transformer Rectifier Unit (TRU) 1 failure.

• Transformer Rectifier Unit (TRU) 1 (A73)
• DC Power Center (DCPC) (A63)
• DC Power Quality Monitor (DCPQM) Card 1
• DC Power Center (DCPC) Electronic Module 1
• DC Power Center (DCPC) Primary Logic Card
• Associated Wiring

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

If the TRU voltage indication on the DC synoptic page is less than 26 volts, suspect a bad or a missing input phase from the AC system (ACPC).

1. Swap the TRU 1 with ESS TRU 1.

   1. If system checks are good, replace TRU 1 and do close out.
   2. If fault remains, continue with next step.
      

2. Check for 115 VAC of TRU voltage input phases.

   1. If voltage are good, go to step 4.
   2. If one or more of the phases are less than 115 VAC, continue with next step.

3. Troubleshoot the power input from the ACPC (AC BUS 2). Repair as required.

   1. If system checks are good, do close out.
   2. If fault remains, continue with next step.

4. Check for 24 VDC at the DCPC input (stud T1) with load on the system.
   NOTE: Use an oscilloscope to take the measurement in order to make sure there is no fluctuation of the DC signal.

   1. If voltage are good, go to step 6.
   2. If one or more of the phases are less than 22 VDC, continue with next step.

5. Perform wiring checks between DCPC and the TRU 1.

   1. If wiring checks are not good, repair defective wiring as required and do close out.
   2. If wiring checks are good, continue with next step.

6. Swap DCPQM card 1 and the DCPQM card 2 in DCPC.

   1. If system checks are good, replace DCPQM card 1 in DCPC and do close out.
   2. If fault remains, continue with next step.

7. In the DCPC, remove the three Primary Logic Cards, the DCPQM card 1 and disconnect connector P105 of Electronic Module 1.
   
8. Perform an EMI filter check by performing a continuity check as follows:

   From	To	Result
   P105-8	Ground
   P105-10	Ground

   1. If there is continuity, go to step 11.
   2. If there is no continuity, continue with next step.

9. Check the resistances of the Electronic Module 1 as follows:

   From	To	Expected Result	Result
   J105-8	J105-9	2 kΩ
   J105-9	J105-10	1.5 kΩ

   1. If resistance is within range, go to step 11.
   2. If resistance is out of range, continue with next step.

10. Replace EM1.

    1. If system checks are good, do close out.
    2. If fault remains, continue with next step.

11. Replace DCPC.
12. Do close out.