SECTION VIII ORGANIZATIONAL AND INTERMEDIATE MAINTENANCE

T.O. 12P4-2APX-192

NAVAIR 16-35TS1843-1

TM 11-6625-1646-25

SECTION VIII

ORGANIZATIONAL AND INTERMEDIATE MAINTENANCE

a. Set BARO SET on the Altimeter/Digitizer to 29.92

8-1. GENERAL.

and read and record the altitude indicated on the altimeter.

8-2. This section contains instructions for performance of

b. Set the AN/APM-123(V) mode switch to C, and the

organizational and intermediate maintenance on Transponder

FUNCTION switch to SYSTEM.

Set, Test Set TS-1843A/APX. Organizational maintenance

c. Set the transponder control MC switch to ON, and

consists of a performance check with the equipment installed

set all mode switches to OUT.

in the aircraft and removal and replacement of the test set, if

d. Set the CODE control setting to the altitude recorded in

defective, from the aircraft.

Intermediate maintenance

step a above. Refer to the chart In paragraph 2-10e of TM 11-

consists of performing an operational bench check, and

6625-667-12 for the reply code setting. The TEST indicator

certain repair procedures authorized at field level.

light on the transponder control and the ACCEPT indicator

8-3. ORGANIZATIONAL MAINTENANCE (ARMY ONLY).

light on the AN/ APM-123(V) should illuminate indicating a go

8-4.

Organizational maintenance consists of running a

condition.

performance check utilizing the AN,"APM-123(V) with the

7. If in any of the above checks, the TEST indicator light fails

equipment installed in the aircraft and interconnected as

to Illuminate and the ACCEPT indicator illuminates, the TS-

shown In figure 6-1. Since operational procedures will vary

1843A is defective. If the TEST indicator light illuminates and

with the type of transponder being used, refer to the AN/APM-

the REJECT indicator light illuminates, both the TS-1843A and

123(V) technical manual (TM-11-6625-667-12) and the

transponder set are defective. If the TEST indicator light falls

applicable transponder maintenance manual.

to illuminate and the REJECT indicator light illuminates, the

8-5. PROCEDURE. If indications specified below are not

transponder system is defective.

obtained, check to ensure that primary power is applied to the

8. Remove the AN,/APM-123(V) from the test set-up. Place

system. Check for proper seating of the RF connectors and

the transponder set control MODE 1 switch In the TEST

the multi-pin connector.

Check the antenna cable and

position; the TEST indicator light should illuminate.

antenna since a high VSWR will cause a no-go indication. If

9. Similarly, place the MODE 2, MODE 3/'A, and MODE C (if

these checks indicate that the remainder of the system is

an altitude digitizer is used in the installation) to the TEST

functioning properly, replace the TS-1843A.

position. The TEST indicator light should illuminate.

1. Set-up the AN, APM-123(V) Test Set as instructed in

10. If the TEST indicator light fails to illuminate In steps 8 and

paragraphs 2-7 and 2-8 of TM 11-6625667-12.

9, the TS-1843A is defective.

2. Set the controls of the AN APM-123(V) to interrogate the

transponder for Mode 1 as instructed in paragraph 2-10 of TM

8-6. INTERMEDIATE MAINTENANCE.

11-6625-667-12.

3. Apply power to the transponder set and place the

transponder control MON-RAD Switch to the MON position.

8-7. This portion of section VIII contains information required

Set all other controls for normal Mode 1 operation. The TEST

by the electronics technician to ensure proper operation,

indicator light on the transponder control and the ACCEPT

repair. and adjustment of the TS1843A and to enable the

indicator light on the AN APM-123(V) should illuminate

technician to use a logical system of troubleshooting. To fully

indicating a go condition.

understand and perform the troubleshooting procedures, the

4. Set the controls of the AN APM-123(V) and the transponder

technician should understand the theory of operation given in

control for Mode 2 Interrogation. The TEST indicator light on

section V. The TS-1843A plug-in assembly locations are

the transponder control and the ACCEPT indicator light on the

shown in figure 8-1; location of components mounted on these

AN/iAPM-123(V) should Illuminate indicating a go condition.

plug-in assemblies are shown in figures 8-2 through 8-4.

Set the controls of the AN,/APM-123(V) and the

Locations of test points is shown In figure 8-5; access to these

transponder control for Mode 3 'A interrogation. The TEST

test points is gained by removing the bottom cover of the unit.

indicator light on the transponder control and the ACCEPT

indicator light on the AN/APM-123(V) should illuminate

8-8. TROUBLESHOOTING. The troubleshooting chart, figure

indicating a go condition.

8-6, is designed to provide a systematic method of locating a

6. If the aircraft is equipped with an altitude digitizer, proceed

faulty module or part within the TS-1843A/APX.

The

with the following check. If it is not so equipped proceed to

basic bench test set-up for troubleshooting the TS-1843A/'APX

step 7 below.

is shown in figure 7-1. The test point indications are listed in

table 8-1.

8-1