Loss of the VDR3 Data Detected by the ATSU

TASK 46-21-00-810-862-A
Loss of the VDR3 Data Detected by the ATSU

1. Possible Causes

XCVR-VHF, 3 [1RC3]
ATSU [1TX1]
wiring of the ATSU COM2 OUTPUT BUS

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 23-12-33-000-001	Removal of the VHF Transceiver
AMM 23-12-33-400-001	Installation of the VHF Transceiver
AMM 46-21-00-740-001	BITE Test of the ATIMS
ASM 462106
AMM 46-21-34-000-001	Removal of the Air Traffic Service Unit (ATSU)
AMM 46-21-34-400-001	Installation of the Air Traffic Service Unit (ATSU)

3. Fault Confirmation
Subtask 46-21-00-875-050-A

A. Table of the circuit breakers used in this procedure:

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C NOT FOR ALL
121VU	COM NAV/VHF/3	2RC3	L05
** ON A/C ALL
121VU	ATSU 1	3TX1	L16
121VU	ATSU 1/SWTG	5TX1	L15
** ON A/C NOT FOR ALL
121VU	COM/VHF/3	2RC3	L05

Subtask 46-21-00-740-170-A

B. Test
(1) Do the BITE test of the ATIMS AMM 46-21-00-740-001.

4. Fault Isolation
Subtask 46-21-00-810-120-A

A. If the test confirms the fault:
(1) Make sure that circuit breakers 2RC3, 3TX1 and 5TX1 are closed.
(a) If the fault continues:

Open and close circuit breaker 2RC3 to reset the VDR3 (VHF3) transceiver.

1 If the fault continues:

Open and close circuit breakers 3TX1 and 5TX1 to reset the ATSU (wait for approximately one minute).

Subtask 46-21-00-810-121-A

B. If the fault continues:

Replace the XCVR-VHF, 3 [1RC3] AMM 23-12-33-000-001 and AMM 23-12-33-400-001.

(1) If the fault continues:

Replace the ATSU [1TX1] AMM 46-21-34-000-001 and AMM 46-21-34-400-001.

(a) If the fault continues:
1 Remove the VDR3 (VHF3) transceiver and the ATSU.
2 Do a check and repair the wiring of the ATSU COM2 OUTPUT BUS between:

Pins AB/1G, 1H of the ATSU and pins AB/12A, 12B of the VDR3 (VHF3) transceiver ASM 462106.

3 Install the VDR3 (VHF3) transceiver and the ATSU.

Subtask 46-21-00-740-171-A

C. Do the test given in Para. 3.

[Rev.8 from Aug 2018] 2026.04.04 04:34:22 UTC