EFFECTIVITY
GJ ALL EXCEPT B-2501 thru
B-2503, B-2509 thru 
B-2510, and B-2524

 Selcal System Schematic  5C8 
23-28-0  Figure 2 (Sheet 3)  Jun 20/88 
Page 6 

SELCAL SYSTEM - TROUBLE SHOOTING
1.  General
A.  Since both SELCAL decoder units are housed in a single case, failure of either SELCAL system requires the entire decoder to be replaced in electronic equipment rack E2. The SELCAL tones may be monitored with the flight interphone system headphones and associated HF and VHF systems to verify whether the decoder is receiving the tones. The SELCAL indicator light comes on and the chime sounds when a SELCAL transmission is received. If the chime sounds but the light does not come on, replace the control panel. If the light comes on but the chime does not sound, replace the aural warning unit. If the light does not come on and the chime does not sound when SELCAL tones are received, replace the decoder.
5C8
Jun 20/85 23-28-0 Page 101
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.

SELCAL SYSTEM - ADJUSTMENT/TEST
1.  Test Selcal System
A.  General
(1)  
The following test is in tended to check for proper operation of the selcal decoders and connected lights and chime whenever a coded signal is received over the respective HF or VHF system.

(2)  
The airplane shall be located with respect to the ground station such that there are no buildings or other obstacles in the transmission path between ground station and airplane.

B.  Equipment Required
(1)  
Selcal Ground Station Encoder - Motorola N-1001A/NA128 (rack-mounted) or N-1000A/NA127 (Console)

(2)  
VHF transmitter

(3)  
HF transmitter

C.  Prepare to Test
(1)  
Connect external power to the airplane.

(2)  
Ensure power is available to load control centers P6 and P18, and both master radio switches are closed.

(3)  
Ensure Selcal, Interphone, HF and VHF circuit breakers are closed.

(4)  
Turn on HF and VHF systems and confirm all systems are operable.

(5)  
Make arrangements for ground operator to transmit selected code signals as necessary. Transmissions shall be made only on authorized frequencies.

D.  Test Selcal System (GJ B-2501 thru B-2503 and B-2509 thru B-2510 and B-2524)
(1)  
Select an authorized test frequency on VHF-1 control panel.

(2)  
Contact ground station and have operator transmit code signal on the desired test frequency.

NOTE:  Airplane selcal code is marked on a placard located on the main instrument panel. Voice communication shall not be made during code transmissions.
(a)  
The selcal No. 1 light should illuminate.

(b)  
The chime shall emit a repetitive tone.

5C8 
Jun 20/88  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  23-28-0 Page 501 

(3)  
Press the RESET button on the control panel. The light should go out and the chimes stop.

(4)  
Repeat steps D.(1) thru D.(3) using HF-1 system. Results should be similar.

(5)  
Repeat steps D.(1) thru D.(3) using VHF-2 system. Results should be similar except that selcal No. 2 light should come on.

(6)  
Repeat steps D.(1) thru D.(3) using HF-2 system. Results should be similar except that selcal No. 2 light should come on.

(7)  
Secure HF and VHF systems.

(8)  
Determine whether there is any further need for electrical power on the airplane; if not, remove external power.

E.  Test Selcal System (GJ ALL EXCEPT B-2501 thru B-2503, B-2509 thru B-2510 and B-2524)
(1)  
Select on authorized test frequency on VHF-1 control panel.

(2)  
Select VHF-1 on SELCAL-1 and SELCAL-2 selector switch.

(3)  
Contact ground station and have operator transmit code signal on the desired test frequency.

NOTE:  Airplane selcal code is marked on a placard located on the main instrument panel. Voice communication shall not be made during code transmissions.
(a)  
Verify selcal No. 1 and No. 2 illuminates.

(b)  
Verify repetitive tone from the aural warning unit.

(4)  
Press the selcal reset buttons and verify the lights go out and tone stops.

(5)  
Repeat steps E.(1) thru E.(4) using VHF-2 system. Results should be similar.

(6)  
Repeat steps E.(1) thru E.(4) using HF-1 system. Results should be similar.

(7)  
Repeat steps E.(1) thru E.(4) using HF-2 system. Results should be similar.
　
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