CHAPTER 4 REPAIRS AND ALIGNMENT

TM 11-6625-667-45/NAVAIR 16-30APM123-2/TO 33A1-3-367-22

CHAPTER 4

REPAIRS AND ALIGNMENT

4-1. General Parts Replacement

soldering gun; damaging voltages can be induced

Techniques

in components.

e. When soldering transistor leads, solder

Most of the parts of Test Set, Transponder

quickly wherever wiring permits, use a heat sink

AN/APM-123V are readily accessible since they

(such as a pair of long nosed pliers between the

are located on pullout circuit boards. Access to

s o l d e r e d joint and the transistor. Use ap-

parts in the transmitter and 28-volt power

p r o x i m a t e l y the same length and dress of

supply, h o w e v e r , requires removal of its

transistor leads as used originally.

respective chassis from the test set for removal

and replacement. All front panel switches require

4-2. Adjustment

removal of one or more subassemblies for access

NOTE

to repair or replace them. After repairing the

4-6 when

See para

using

equipment, the adjustments in paragraph 4-2

AN/TPM-25A.

should be performed. The precautions in a

through e below apply specifically to this test set.

After a circuit in a fictional section is repaired,

a. Do not disturb the adjustment of preselector

the functional section should be adjusted to

A15Z1 (fig. 3-6). It was adjusted at the factory.

insure proper equipment operation. Two ad

This adjustment is extremely critital, and special

justment procedures are provided for the tran-

test equipment is required to test it or to perform

smitter, receiver and decoder functional sections

an adjustment. Adjustment of this preselector

to use either conventional test equipment and the

will void the entire calibration of the unit. If this

Radar Test Set AN/UPM-98 or the Radar Test

part appears faulty, it should be replaced with a

Set AN/UPM-137A. The functional sections are

new one.

listed below together with the reference to the

b. Do not disturb the settings of controls A5R1

paragraph containing the adjustment procedures.

through A5R6 and A7R1 through A7R14 (fig.

a. Power supply section (para 4-3).

3-7). These adjustments were performed at the

b. Transmitter section (para 4-4 and para

factory a n d are extremely critical. Any

4-4.1).

movement of one or more controls will void the

c. Receiver and decoder section (para 4-5 and

entire calibration of the unit.

4-5.1)

CAUTION

4-3. Power Supply Adjustments

If control A16A2R1 of the transmitter

a. Test Equipment Required. Multimeter

voltage regulator is adjusted to a

ME-26B/U is required.

v o l t a g e greater than specified it will

b. Test Setup. The test setup is shown in figure

degrade and shorten the transmitter

3-1. The ME-26B/U is connected as specified in c

electron tube performance and life.

below. Refer to figure 3-6 for test point location

c. Do not adjust control A16A2R1 (fig, 8-25) of

and figure 3-7 for adjustment control location.

the transmitter voltage regulator without first

c. Procedure

r e f e r r i n g to the instructions o u t l i n e d in

(1) Set the ME-26B/U SELECTOR control

paragraph 4-4c. This adjustment can void the

to(+) and RANGE control to 300V.

calibration of this equipment.

(2) Connect the ME-26B/U common lead to

d. Use a pencil type soldering iron with a 25-

test point A13TP2 (ground and the dc probe to

watt maximum capacity. This test set is tran-

test point A14TP3.

sistorized. If the soldering iron must be used with

(3) Apply power to the test set.

alternating current (ac, use an isolating trans-

(4) Adjust A14R8 until the meter indicates

former between it and the line. Do not use a

+ 150 2 volts.

Change 5 4-1