Fault Message:

ESS TRU 2 FAILED/WRG/ESS TRU 2 FEED

Fault Code:

2460473DCP

Associated CAS:

ELEC SYS FAULT
(Advisory)

DC Power Center (DCPC) has detected a Essential Transformer Rectifier Unit (ESS TRU) 2 failure.

• Essential Transformer Rectifier Unit (ESS TRU) 2 (A76)
• DC Power Center (DCPC) DC Power Quality Monitor (DCPQM) Card 2
• Alternate DC Power Distribution (ADCPD) 2
• DC Power Center (DCPC) Electronic Module (EM4)
• DC Power Center (DCPC) Primary Logic Cards
• DC Power Center (DCPC) (A63)
• 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 ESS TRU 2 with TRU 2.

   1. If system checks are good, replace ESS TRU 2 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 4).

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

4. Check for 24 VDC at the DCPC input (stud T14) 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 24 VDC, continue with next step.

5. Perform wiring checks between DCPC and the ESS TRU including the ADCPD 2.

   1. If wiring checks are good, repair defective wiring as required and do close out.
   2. If wiring checks are good, continue with next step.

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

   1. If system checks are good, replace DCPQM card 2 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 2 and disconnect connector P407 of Electronic Module 4.
8. Perform an EMI filter check by performing a continuity check as follows:

   From	To	Result
   P407-8	Ground
   P407-10	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
   J407-8	J407-9	2 KOhms
   J407-9	J407-10	1.5 KOhms

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

10. Replace EM 4.

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

11. Replace DCPC.
12. Do close out.