Loss of the Power Supply of the MCDU 2

TASK 22-82-00-810-805-A
Loss of the Power Supply of the MCDU 2

1. Possible Causes

MCDU-2 [3CA2]
wiring of the 115VAC signal from the circuit breaker 11CA2 to the MCDU 2 (3CA2)
wiring of the ground signal at MCDU 2 (3CA2)
C/B-AUTO FLT/MCDU/2 [11CA2]

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 22-82-00-865-062-A

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

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C ALL
121VU	AUTO FLT/MCDU/2	11CA2	N20

Subtask 22-82-00-710-058-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 11CA2 is open, refer to Para. 4.B.

4. Fault Isolation
Subtask 22-82-00-810-056-A

A. If the circuit breaker 11CA2 is closed and if the MCDU MENU page is not in view on the MCDU 2:

do a check for 115VAC at MCDU 2 (3CA2).

(1) If there is 115VAC:

replace the MCDU-2 [3CA2] , 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 11CA2 to the MCDU 2 (3CA2)
do a check of the wiring of the ground signal at MCDU 2 (3CA2) 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/2 [11CA2] .

Subtask 22-82-00-810-057-A

B. If the circuit breaker 11CA2 is open:

close the circuit breaker.

(1) If the circuit breaker is open again:

replace the MCDU-2 [3CA2] , 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 (11CA2) to the MCDU 2 (3CA2) 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/2 [11CA2] .

Subtask 22-82-00-710-059-A

C. Do the test given in Para. 3.

[Rev.8 from Aug 2018] 2026.04.04 04:25:27 UTC