EPSU - Emergency Power-Supply Unit Fault

TASK 33-51-00-810-801-A
EPSU - Emergency Power-Supply Unit Fault

1. Possible Causes

POWER-EMERGENCY SUPPLY [10WL]
signs and lights
wiring
EPSU [11WL]
EPSU [12WL]
EPSU [13WL]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 33-51-00-710-001	Operational Test of the Emergency Lights
ASM 335101
ASM 335102
ASM 335104
AMM 33-51-38-000-001	Removal of the Emergency Power-Supply Unit (EPSU)
AMM 33-51-38-400-001	Installation of the Emergency Power-Supply Unit (EPSU)

3. Fault Confirmation

CAUTION: DO NOT USE THE TEACH-IN PROCEDURE AS AN ALTERNATIVE FOR TROUBLESHOOTING. A TEACH-IN PROCEDURE IS NOT A RESET PROCEDURE. BEFORE YOU DO A TEACH-IN PROCEDURE, MAKE SURE THAT YOU CORRECTED ALL FAILURES. IF YOU DO NOT OBEY THIS, FAILURES CAN CAUSE A MALFUNCTION OF THE CABIN EMERGENCY LIGHTING SYSTEM.

Subtask 33-51-00-710-050-A ** ON A/C NOT FOR ALL

A. Do the operational test of the emergency lighting system AMM 33-51-00-710-001.

4. Fault Isolation
Subtask 33-51-00-810-067-A ** ON A/C NOT FOR ALL

A. If the test gives a different maintenance message, do the trouble shooting procedure related to the maintenance message.

Subtask 33-51-00-810-050-A ** ON A/C NOT FOR ALL

B. If the operational test gives the maintenance message:
(1) EPSU UNIT FWD L:

replace the POWER-EMERGENCY SUPPLY [10WL] AMM 33-51-38-000-001 and AMM 33-51-38-400-001.

(a) If the fault continues:

check all connected signs and lights for a short-circuit and replace if necessary ASM 335101 and ASM 335104,
if you find one or more defective signs and lights, replace the POWER-EMERGENCY SUPPLY [10WL] AMM 33-51-38-000-001 and AMM 33-51-38-400-001.

(b) If the fault continues:

do a check for a short to ground and repair the wiring if necessary ASM 335101 and ASM 335104:
from EPSU (10WL) pin E to the connector(s) of the related signs and lights,
from EPSU (10WL) pin F to the connector(s) of the related signs and lights,
from EPSU (10WL) pin G to the connector(s) of the related signs and lights,
from EPSU (10WL) pin N to the connector(s) of the related signs and lights,
from EPSU (10WL) pin R to the connector(s) of the related signs and lights,
from EPSU (10WL) pin T to the connector(s) of the related signs and lights,
from EPSU (10WL) pin -B to the connector(s) of the related signs and lights,
from EPSU (10WL) pin -J to the connector(s) of the related signs and lights,
if you find a short to ground in the wiring, replace the POWER-EMERGENCY SUPPLY [10WL] AMM 33-51-38-000-001 and AMM 33-51-38-400-001.

do a check and repair the wiring if necessary ASM 335101:
from EPSU (10WL) pin -P to DEU-B (300RH1) pin B/17,
from EPSU (10WL) pin X to DEU-B (300RH1) pin B/16,
from EPSU (10WL) pin L to GND,
from EPSU (10WL) pin M to GND,
from EPSU (10WL) pin U to GND,
from EPSU (10WL) pin -R to GND,
from EPSU (10WL) pin -M to GND.

(2) EPSU UNIT EMER L:

replace the EPSU [11WL] AMM 33-51-38-000-001 and AMM 33-51-38-400-001.

(a) If the fault continues:

check all connected signs and lights for a short-circuit and replace if necessary ASM 335102 and ASM 335104,
if you find one or more defective signs and lights, replace the EPSU [11WL] AMM 33-51-38-000-001 and AMM 33-51-38-400-001.

(b) If the fault continues:

do a check for a short to ground and repair the wiring if necessary ASM 335102 and ASM 335104:
from EPSU (11WL) pin E to the connector(s) of the related signs and lights,
from EPSU (11WL) pin F to the connector(s) of the related signs and lights,
from EPSU (11WL) pin G to the connector(s) of the related signs and lights,
from EPSU (11WL) pin N to the connector(s) of the related signs and lights,
from EPSU (11WL) pin R to the connector(s) of the related signs and lights,
from EPSU (11WL) pin T to the connector(s) of the related signs and lights,
from EPSU (11WL) pin -B to the connector(s) of the related signs and lights,
from EPSU (11WL) pin -J to the connector(s) of the related signs and lights,
if you find a short to ground in the wiring, replace the EPSU [11WL] AMM 33-51-38-000-001 and AMM 33-51-38-400-001.

do a check and repair the wiring if necessary ASM 335102:
from EPSU (11WL) pin -P to DEU-B (300RH4) pin B/17,
from EPSU (11WL) pin X to DEU-B (300RH4) pin B/16,
from EPSU (11WL) pin L to GND,
from EPSU (11WL) pin M to GND,
from EPSU (11WL) pin U to GND,
from EPSU (11WL) pin -R to GND,
from EPSU (11WL) pin -M to GND.

(3) EPSU UNIT EMER R:

replace the EPSU [12WL] AMM 33-51-38-000-001 and AMM 33-51-38-400-001.

(a) If the fault continues:

check all connected signs and lights for a short-circuit and replace if necessary ASM 335102 and ASM 335104,
if you find one or more defective signs and lights, replace the EPSU [12WL] AMM 33-51-38-000-001 and AMM 33-51-38-400-001.

(b) If the fault continues:

do a check for a short to ground and repair the wiring if necessary ASM 335102 and ASM 335104:
from EPSU (12WL) pin E to the connector(s) of the related signs and lights,
from EPSU (12WL) pin F to the connector(s) of the related signs and lights,
from EPSU (12WL) pin G to the connector(s) of the related signs and lights,
from EPSU (12WL) pin N to the connector(s) of the related signs and lights,
from EPSU (12WL) pin R to the connector(s) of the related signs and lights,
from EPSU (12WL) pin T to the connector(s) of the related signs and lights,
from EPSU (12WL) pin -B to the connector(s) of the related signs and lights,
from EPSU (12WL) pin -J to the connector(s) of the related signs and lights,
if you find a short to ground in the wiring, replace the EPSU [12WL] AMM 33-51-38-000-001 and AMM 33-51-38-400-001.

do a check and repair the wiring if necessary ASM 335102:
from EPSU (12WL) pin -P to DEU-B (300RH4) pin B/20,
from EPSU (12WL) pin X to DEU-B (300RH4) pin B/19,
from EPSU (12WL) pin L to GND,
from EPSU (12WL) pin M to GND,
from EPSU (12WL) pin U to GND,
from EPSU (12WL) pin -R to GND,
from EPSU (12WL) pin -M to GND.

(4) EPSU UNIT AFT L:

replace the EPSU [13WL] AMM 33-51-38-000-001 and AMM 33-51-38-400-001.

(a) If the fault continues:

check all connected signs and lights for a short-circuit and replace if necessary ASM 335102 and ASM 335104,
if you find one or more defective signs and lights, replace the EPSU [13WL] AMM 33-51-38-000-001 and AMM 33-51-38-400-001.

(b) If the fault continues:

do a check for a short to ground and repair the wiring if necessary ASM 335102 and ASM 335104:
from EPSU (13WL) pin E to the connector(s) of the related signs and lights,
from EPSU (13WL) pin F to the connector(s) of the related signs and lights,
from EPSU (13WL) pin G to the connector(s) of the related signs and lights,
from EPSU (13WL) pin N to the connector(s) of the related signs and lights,
from EPSU (13WL) pin R to the connector(s) of the related signs and lights,
from EPSU (13WL) pin T to the connector(s) of the related signs and lights,
from EPSU (13WL) pin -B to the connector(s) of the related signs and lights,
from EPSU (13WL) pin -J to the connector(s) of the related signs and lights,
if you find a short to ground in the wiring, replace the EPSU [13WL] AMM 33-51-38-000-001 and AMM 33-51-38-400-001.

do a check and repair the wiring if necessary ASM 335102:
from EPSU (13WL) pin -P to DEU-B (300RH5) pin B/17,
from EPSU (13WL) pin X to DEU-B (300RH5) pin B/16,
from EPSU (13WL) pin L to GND,
from EPSU (13WL) pin M to GND,
from EPSU (13WL) pin U to GND,
from EPSU (13WL) pin -R to GND,
from EPSU (13WL) pin -M to GND.

Subtask 33-51-00-710-051-A ** ON A/C NOT FOR ALL

C. Do the test as given in the Para. 3.A.

5. Close-up
Subtask 33-51-00-860-064-A ** ON A/C NOT FOR ALL

A. Put the aircraft back to its initial configuration.

[Rev.8 from Aug 2018] 2026.04.04 04:32:06 UTC