Loss of the VDR3 Data Detected by the ATSU

TASK 46-21-00-810-815-A
Loss of the VDR3 Data Detected by the ATSU

1. Possible Causes

XCVR-VHF, 3 [1RC3]
ATSU [1TX1]
wiring of the VHF3 DATA 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 462105
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 46-21-00-865-050-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 46-21-00-740-076-A

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

4. Fault Isolation
Subtask 46-21-00-810-063-A

A. If the test gives the maintenance message VDR3(1RC3)/ATSU1(1TX1):
(1) make sure that the circuit breakers 2RC3, 3TX1 and 5TX1 are closed.
(a) If the fault continues:

open and close the circuit breaker 2RC3 to reset the VHF3.

1 If the fault continues:

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

(2) If the fault continues:

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

(a) If the fault continues:

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

1 If the fault continues:

remove the VDR 3 (VHF3 transceiver) and the ATSU
do a check and repair the wiring of the VHF3 DATA BUS : between pins AB/10C,10D of the VDR 3 (VHF3 transceiver) and pins AA/4J,4K of the ATSU ASM 462105
install the VDR 3 (VHF3 transceiver) and the ATSU.

Subtask 46-21-00-740-077-A

B. Do the test given in Para. 3.

[Rev.8 from Aug 2018] 2026.04.04 04:34:18 UTC