Failure of the VHF 3 Transceiver

TASK 23-12-00-810-803-A
Failure of the VHF 3 Transceiver

1. Possible Causes

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 23-12-00-740-001	BITE Test of the VHF System
ASM 231203
AMM 23-12-33-000-001	Removal of the VHF Transceiver
AMM 23-12-33-400-001	Installation of the VHF Transceiver

3. Fault Confirmation
Subtask 23-12-00-740-054-A

A. Test
Do the BITE test of the VHF system AMM 23-12-00-740-001.

NOTE: Do this test for the VHF 3 only.

4. Fault Isolation
Subtask 23-12-00-865-063-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 NOT FOR ALL
121VU	COM/VHF/3	2RC3	L05

Subtask 23-12-00-810-052-C

B. If the test gives the maintenance message VHF3 (1RC3):

(1) If the circuit breaker is closed:

(a) If there is 28DC:

(b) If there is no 28DC:

do a check for a ground signal at pin AB/3D of the VHF 3 transceiver (1RC3) ASM 231203.

1 If there is no ground signal:

repair the wiring between the VHF 3 transceiver pin AB/3D and the ground terminal ASM 231203.

2 If there is a ground signal:

do a check of the wiring between the VHF 3 transceiver pin AC/2 and the circuit breaker 2RC3 ASM 231203.

a If there is no continuity:

b If there is continuity:

(2) If the circuit breaker is open:

(a) If it opens again:

1 If the fault continues:

do a check for a short-to-ground at the wiring between the VHF 3 transceiver pin AC/2 and the circuit breaker 2RC3 ASM 231203.

a If there is a short-to-ground:

b If there is no short-to-ground:

(b) If the circuit breaker stays closed and the fault continues:

Subtask 23-12-00-740-055-A

C. Do the test given in Para. 3.

[Rev.8 from Aug 2018] 2026.04.04 04:25:36 UTC