Loss of the Power Supply of the MCDU 1

TASK 22-82-00-810-801-A
Loss of the Power Supply of the MCDU 1

1. Possible Causes

MCDU-1 [3CA1]
wiring of the 115VAC signal from the circuit breaker 11CA1 to the MCDU 1 (3CA1)
wiring of the ground signal at MCDU 1 (3CA1)
C/B-AUTO FLT/MCDU/1 [11CA1]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 22-70-00-710-001	Operational Test of the Multipurpose Control and Display Unit (MCDU)
AMM 22-82-12-000-001	Removal of the MCDU
AMM 22-82-12-400-002	Installation of the MCDU
ASM 228402

3. Fault Confirmation
Subtask 22-82-00-865-061-A

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

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C ALL
49VU	AUTO FLT/MCDU/1	11CA1	B01

Subtask 22-82-00-710-050-A

B. Test
(1) Do the operational test of the multipurpose control and display unit (MCDU) AMM 22-70-00-710-001.
(a) If the circuit breaker 11CA1 is open, refer to Para. 4.B.

4. Fault Isolation
Subtask 22-82-00-810-050-A

A. If the circuit breaker 11CA1 is closed and if the MCDU MENU page is not in view on the MCDU 1:

do a check for 115VAC at MCDU 1 (3CA1).

(1) If there is 115VAC:

replace the MCDU-1 [3CA1] , AMM 22-82-12-000-001 and AMM 22-82-12-400-002.

(2) If there is no 115VAC:

do a check of the wiring of the 115VAC signal from the circuit breaker 11CA1 to the MCDU 1 (3CA1)
do a check of the wiring of the ground signal at MCDU 1 (3CA1) pin A/41.
ASM 228402.

(a) If there is no continuity:

repair the above wirings.

(b) If there is continuity:

replace the C/B-AUTO FLT/MCDU/1 [11CA1] .

Subtask 22-82-00-810-051-A

B. If the circuit breaker 11CA1 is open:

close the circuit breaker.

(1) If the circuit breaker is open again:

replace the MCDU-1 [3CA1] , AMM 22-82-12-000-001 and AMM 22-82-12-400-002.

(a) If the fault continues:

do a check for a short to ground between the circuit breaker (11CA1) to the MCDU 1 (3CA1) ASM 228402.

1 If there is a short to ground:

repair the above wiring.

2 If there is no short to ground:

replace the C/B-AUTO FLT/MCDU/1 [11CA1] .

Subtask 22-82-00-710-051-A

C. Do the test given in Para. 3.

[Rev.8 from Aug 2018] 2026.04.04 04:25:26 UTC