Fault Message:

ESS TRU 1 FAILED/WRG/ESS TRU 1 FEED

Fault Code:

2460471DCP

Associated CAS:

ELEC SYS FAULT
(Advisory)

The DC Power Center (DCPC) has detected an Essential Transformer Rectifier Unit (ESS TRU) 1 failure.

• Essential Transformer Rectifier Unit (ESS TRU) 1 (A75)
• DC Power Center (DCPC) DC Power Quality Monitor (DCPQM) Card 1
• Alternate DC Power Distribution (ADCPD) 1
• DC Power Center (DCPC) Electronic Module (EM3)
• DC Power Center (DCPC) Primary Logic Cards
• DC Power Center (DCPC) (A63)
• Associated Wiring

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

NOTE: 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. With power ON, cycle the DC override switch to actuate relays K53 and K52.

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

2. Swap ESS TRU 1 with TRU 1.

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

3. Check the 3 TRU input phases and make sure you read 115 VAC on each phase.

   1. If system checks are good, go to step 5.
   2. If one or more of the phases are less than 115 VAC, continue with next step.

4. Troubleshoot the power input from the ACPC (AC BUS 1).

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

5. Perform a voltage check at the DCPC input (stud T3) with load on the system. Use an oscilloscope to take the measurement in order to make sure there is no fluctuation of the DC signal.

   1. If you read greater than 22 Volts, go to step 7.
   2. If you read less than 22 Volts, continue with next step.

6. Perform a wiring check between the DCPC and the ESS TRU including the ADCPD 1.

   1. If wiring checks are good, suspect relay K53 inside ADCPD 1 and do close out.
   2. If wiring checks are not good, continue with next step.

7. In the DCPC, swap the DCPQM card 1 and the DCPQM card 2.

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

8. In the DCPC, remove the three Primary Logic Cards, the DCPQM card 1 and disconnect connector P305 of Electronic Module 3.
9. Perform an EMI filter check by performing a continuity check as follows:

   From	To	Result
   P305-8	Ground
   P305-10	Ground

   1. If there is continuity, go to step 12.
   2. If there is no continuity, continue with next step.

10. Verify the resistances of the Electronic Module 3 and perform a resistance check as follows:

    From	To	Expected Result	Result
    J305-8	J305-9	2 KOhms
    J305-9	J305-10	1.5 KOhms

    1. If resistance is within range, go to step 12.
    2. If resistance is out of range, continue with next step.

11. Replace the EM 3.

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

12. Replace the DCPC.
13. Do close out.