No Electrical Power from FWD Master Control Unit (MCU)

TASK 25-21-00-810-865-A
No Electrical Power from FWD Master Control Unit (MCU)

1. Possible Causes

MASTER CONTROL UNIT - SEAT POWER SUPPLY [55HP1]
MASTER CONTROL UNIT - SEAT POWER SUPPLY [55HP2]
wiring

2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment

REFERENCE	QTY	DESIGNATION
No specific	1	MULTIMETER - STANDARD

B. 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 252131
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 25-21-00-710-094-C ** ON A/C NOT FOR ALL

A. Make sure that these switches are in the ON position:

The PED POWER switch on the FAP (PED power is supplied through the CIDS system)

Subtask 25-21-00-740-051-A ** ON A/C NOT FOR ALL

B. Do the BITE Test of the forward Master Control Unit (MCU) (55HP1) AMM 25-21-00-740-001

4. Fault Isolation
Subtask 25-21-00-810-239-C ** ON A/C NOT FOR ALL

A. If there is no electrical power from the MCUs 55HP1 and/ or 55HP2, do the procedure as follows:
(1) At the MCU 55HP1:

Disconnect the applicable connector.
Use the MULTIMETER - STANDARD and do the check to make sure that 115V AC is available at the applicable power outlet of the MCU 55HP1.

(2) If there is no 115V AC available, replace the MASTER CONTROL UNIT - SEAT POWER SUPPLY [55HP1] AMM 25-21-34-000-001 and AMM 25-21-34-400-001.
(3) At the MCU 55HP2:

Disconnect the applicable connector.
Use the MULTIMETER - STANDARD and do the check to make sure that 115V AC is available at the applicable power outlet of the MCU 55HP2.

(4) If there is no 115V AC available, replace the MASTER CONTROL UNIT - SEAT POWER SUPPLY [55HP2] AMM 25-21-34-000-001 and AMM 25-21-34-400-001.

Subtask 25-21-00-810-239-E ** 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 58HP 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 252131.
(2) If the GENERAL BITE LED is OFF:
(a) Replace the MASTER CONTROL UNIT - SEAT POWER SUPPLY [55HP1] 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 (55HP1) AMM 25-21-34-000-001 and AMM 25-21-34-400-001.

Subtask 25-21-00-710-095-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