No Electrical Power from the aft Master Control Unit (MCU)

TASK 25-21-00-810-869-A
No Electrical Power from the aft Master Control Unit (MCU)

1. Possible Causes

MASTER CONTROL UNIT - SEAT POWER SUPPLY [55HP2]
wiring

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
TSM TASK 24-00-00-810-803-A	Circuit Breaker Tripped and/or C/B TRIPPED Warning
ASM 252100
AMM 25-21-00-740-001	BITE Test of the Master Control Unit (MCU)
AWM 252132
AMM 25-21-34-000-001	Removal of the Master Control Unit (MCU)
AMM 25-21-34-400-001	Installation of the Master Control Unit (MCU)

3. Fault Confirmation
Subtask 25-21-00-740-052-A ** ON A/C NOT FOR ALL

A. Do the BITE Test of the aft Master Control Unit (MCU) (55HP2) AMM 25-21-00-740-001.

4. Fault Isolation
Subtask 25-21-00-810-243-D ** ON A/C NOT FOR ALL

A. If the test confirms the fault, refer to the MCU indication panel:
(1) If the POWER STATE LED is OFF:
(a) Make sure that the PAX SYS switch is in the ON position.
(b) If the fault continues:
(c) Do a check of the circuit breaker 59HP on the panel 2000VU:
1 If it is closed, make sure that the busbar 220XP is energized.
2 If it is open, do a check of the wiring between the circuit breaker panel and the MCU (Ref. TSM TASK 24-00-00-810-803) AWM 252132.
(2) If the GENERAL BITE LED is OFF:
(a) Replace the MASTER CONTROL UNIT - SEAT POWER SUPPLY [55HP2] AMM 25-21-34-000-001 and AMM 25-21-34-400-001.
(3) If the GENERAL BITE and the PORT BITE LEDs are OFF:
(a) Do a check and repair the wiring (Ref. TSM TASK 24-00-00-810-803) ASM 252100.
(4) If the PORT POWER STATUS LEDs are OFF:
(a) Replace the MCU (55HP2) AMM 25-21-34-000-001 and AMM 25-21-34-400-001.

Subtask 25-21-00-710-105-A ** ON A/C NOT FOR ALL

B. Do the test given in Para. 3.

[Rev.8 from Aug 2018] 2026.04.04 04:27:01 UTC