Failure of the DC supply 401PP

TASK 32-43-00-810-832-A
Failure of the DC supply 401PP

1. Possible Causes

ABCU [95GG]
wiring from ABCU (95GG) pin A/B to the ground terminal
C/B-ABCU &/Y BRK/PRESS IND [61GG]
IND-BRK YELLOW PRESS TRIPLE [60GG]
PRESS XDCR-BRK, YELLOW R [100GG]
PRESS XDCR-BRK, YELLOW L [101GG]
HYDR. PRESSURE TRANSMITTER [3068GN]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
TSM TASK 32-43-00-810-822-A	Loss of left alternate braking or right alternate braking detected by the ABCU
AMM 29-32-11-000-001	Removal of the Hydraulic Pressure Transducer
AMM 29-32-11-400-001	Installation of the Hydraulic Pressure Transducer
ASM 324301
ASM 324303
AMM 32-43-34-000-001	Removal of the Alternate Braking Control Unit (ABCU)
AMM 32-43-34-400-001	Installation of the Alternate Braking Control Unit (ABCU)
ASM 324401
AMM 32-44-19-000-001	Removal of the Pressure Transducer
AMM 32-44-19-400-001	Installation of the Pressure Transducer
AMM 32-44-21-000-001	Removal of the Brake Yellow Pressure Triple Indicator
AMM 32-44-21-400-001	Installation of the Brake Yellow Pressure Triple Indicator
ASM 324501
AMM 32-46-00-740-001	BITE Test of the BSCU
AMM 32-46-00-740-002	BITE Test of the BSCU - Ground Scanning

3. Fault Confirmation
Subtask 32-43-00-740-078-A ** ON A/C NOT FOR ALL

A. Test
(1) Do the BITE test of the BSCU (GROUND SCANNING) with the parking brake ON AMM 32-46-00-740-002.
(2) If the BITE test (GROUND SCANNING) gives the maintenance message ABCU(95GG)/BRK ALTN PEDAL XMTR (103GG):

Do the related trouble shooting procedure (Ref. TSM TASK 32-43-00-810-822).

(3) Do the BITE test of the BSCU (GROUND SCANNING) with the parking brake OFF AMM 32-46-00-740-002.
(4) If the BITE test (GROUND SCANNING) gives the maintenance message ABCU(95GG) DC SPLY 401PP:

Go to the Para. Fault Isolation

4. Fault Isolation
Subtask 32-43-00-865-050-A ** ON A/C NOT FOR ALL

A. Make sure that this(these) circuit breaker(s) is(are) closed:

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C NOT FOR ALL
49VU	ABCU &/Y BRK/PRESS IND	61GG	C10

Subtask 32-43-00-810-081-A ** ON A/C NOT FOR ALL

B. Test
(1) Do a reset of the BSCU with the A/SKID AND NOSE WHEEL switch (5GG).
(2) Do the BITE test of the BSCU AMM 32-46-00-740-001
(3) Do a check of the status of the circuit breaker (61GG).

Subtask 32-43-00-810-083-A ** ON A/C NOT FOR ALL

C. If the circuit breaker (61GG) is closed:
(1) If there is 28VDC:
(a) Do a check for a ground signal at pin A/B of the ABCU (95GG)
1 If there is a ground signal:

Replace the ABCU [95GG] AMM 32-43-34-000-001 AMM 32-43-34-400-001

2 If there is no ground signal:

Repair the wiring from the pin A/B of the ABCU (95GG) to the ground terminal ASM 324303.

(2) If there is no 28VDC:

Do a check for a ground signal at pin A/B of the ABCU (95GG) ASM 324303

(a) If there is no ground signal:

Repair the wiring from ABCU (95GG) pin A/B to the ground terminal ASM 324303

(b) If there is a ground signal:

Replace the C/B-ABCU &/Y BRK/PRESS IND [61GG] ASM 324303

Replace the ABCU [95GG] AMM 32-43-34-000-001 and AMM 32-43-34-400-001.

Subtask 32-43-00-810-084-A ** ON A/C NOT FOR ALL

D. If the circuit breaker (61GG) is open:
(1) Remove the ABCU (95GG) AMM 32-43-34-000-001.
(2) Disconnect the connector A of this unit:

INDICATOR (60GG).

(3) Disconnect the connector A of this unit:

PRESS XDCR (101GG).

(4) Disconnect the connector A of this unit:

PRESS XDCR (100GG).

(5) Disconnect the connector A of this unit:

PRESS XDCR (3068GN).

(6) Do a check for short circuit of the wiring between the ABCU (95GG) and INDICATOR (60GG) and PRESS XDCR (101GG, 100GG, 3068GN).
(a) If there is a short circuit:
1 Repair the wiring.
2 Connect the connector A of this unit:

INDICATOR (60GG).

3 Connect the connector A of this unit:

PRESS XDCR (101GG).

4 Connect the connector A of this unit:

PRESS XDCR (100GG).

5 Connect the connector A of this unit:

PRESS XDCR (3068GN).

6 Install the ABCU (95GG) AMM 32-43-34-400-001.
(b) If there is no short circuit:

Close the circuit breaker (61GG).

(7) If the circuit breaker (61GG) stays closed:
(a) Connect the units one after the other until the circuit breaker (61GG) trips again, replace the related unit:

For the ABCU [95GG] AMM 32-43-34-000-001 AMM 32-43-34-400-001
For the IND-BRK YELLOW PRESS TRIPLE [60GG] AMM 32-44-21-000-001 AMM 32-44-21-400-001
For the PRESS XDCR-BRK, YELLOW R [100GG] and for PRESS XDCR-BRK, YELLOW L [101GG] AMM 32-44-19-000-001 AMM 32-44-19-400-001
For the HYDR. PRESSURE TRANSMITTER [3068GN] AMM 29-32-11-000-001 AMM 29-32-11-400-001.

(b) Connect all the units.
(8) If the circuit breaker (61GG) trips again:

Do a check for a short circuit to ground at wiring between the circuit breaker (61GG) and the five units ASM 324301 ASM 324401 ASM 324501.

(a) If there is a short circuit to ground:

Repair the related wiring.
Replace the C/B-ABCU &/Y BRK/PRESS IND [61GG] ASM 324301.

Subtask 32-43-00-740-087-A ** ON A/C NOT FOR ALL

E. If the BITE test (GROUND SCANNING) gives the maintenance message ABCU (95GG)/DC SUPPLY 401PP:

Replace the ABCU [95GG] AMM 32-43-34-000-001 AMM 32-43-34-400-001.

Subtask 32-43-00-740-079-A ** ON A/C NOT FOR ALL

F. After the subsequent flight, make sure that the fault does not continue.

[Rev.8 from Aug 2018] 2026.04.04 04:31:42 UTC