If. Amplifier PCB Test Procedure

TM 11-5825-270-23

4-24. If. Amplifier PCB Test Procedure

(12) Reduce the signal generator output level by

the threshold set by CARRIER control A2R22 (-2 to -10

a. Test Equipment and Material.

dB).

(13) The voltage at A2TP5 should be 0 Vdc.

(1) Multimeter AN/USM-223

Adjust CARRIER control A2R22 clockwise until the

(2) Test Set SG-1128/U

b. Test Connections and Conditions.

voltage at A2TP5 switches to +12 Vdc. Then adjust

clockwise or counterclockwise to the position where the

(1) Set the POWER switch to OFF.

voltage is 0 Vdc, but any further clockwise movement

(2) Connect the signal generator to J1 of the

switches the voltage to +12 Vdc.

monitor receiver. Set the signal generator frequency to

(14) Increase the signal generator output by 0.5

the receiver frequency with an unmodulated rf output of

dB. The voltage at A2TP5 will switch to +12 Vdc.

100 mV.

(15) Set the signal generator output to 100 mV.

(3) Check that TP2, TP5 and TP8 have the

(16) Set TIME DELAY control A2R32 (fig. 2-1) to

correct connections (fig. 2-1). For carrier alarm only

the delay required (0-60).

connect TP5 to TP8. For carrier and modulation alarm

(17) Press the ALARM TEST switch. Within

only connect TP5 to TP8.

20% of the time set by TIME DELAY control A2R32,

(4) The equipment should have all other

the ALARM indicator will go on and the NORM alarm will

connections as for its operational condition.

c. Procedure.

go off.

(18) Release the ALARM TEST switch. The

(1) Set the POWER switch to ON, then

ALARM indicator will go off and the NORM indicator will

momentarily press the ALARM SIL switch.

go on immediately.

(2) Set the RF ATTEN control (fig. 2-1) to 60.

(19) Set the signal generator to 15% modulation

(3) Adjust the signal generator frequency to get

at 1 kHz.

the maximum CARRIER LEVEL meter reading.

(20) Simulate keying by switching the signal

(4) Adjust SENSITIVITY control A3R7 (fig. 2-1)

generator modulation control on and off. The period

to get a reading of approximately 0 db on the CARRIER

between key-off and key-on must be less than the time

LEVEL meter.

delay set by TIME DELAY control A2R32. The receiver

(5) Adjust RF TUNE control (fig. 2-1) to get a

will generate an alarm.

maximum reading on the CARRIER LEVEL meter.

(21) Switch the signal generator modulation off.

(6) Adjust A2C2, A2C3 and A2C10 (fig. 2-1) in

Within 20% of the time set by TIME DELAY control

turn, starting with C2, to maximize the CARRIER LEVEL

A2R32, the ALARM indicator will go on and the NORM

meter reading. If the meter reading exceeds +10 dB

indicator will go off.

adjust SENSITIVITY control A3R7 counterclockwise to

(22) Simulate keying by switching the signal

get a reading of 0 dB, and complete the adjustment

generator modulation control on and off. The NORM

procedure of A2C2, A2C3 and A2C10.

indicator will come on and the ALARM indicator will go

(7) Set CARRIER control A2R22 (fig. 2-1) fully

off.

counterclockwise.

(23) Set the signal generator modulation control

(8) Connect the oscilloscope between A2TP5

to on. Within 20% of the time set by TIME DELAY

(+) and A2TP9 (-) (fig. 2-1). The voltage will be +12 Vdc.

control A2R32, the ALARM indicator will go on and the

(9) Adjust

SENSITIVITY

control

A3R7

NORM indicator will go off

counterclockwise until the voltage at A2TP5 switches to

(24) Carefully adjust the RF TUNE control to get

0 Vdc.

a maximum reading on the CARRIER LEVEL meter.

(10) Adjust SENSITIVITY control A3R7 clockwise

(25) Adjust SENSITIVITY control A3R7 to get a

or counterclockwise so that the voltage at A2TP5

CARRIER LEVEL meter reading of 0 dB.

switches to +12 Vdc.

Adjust so that any further

(26) With TB1 terminals 1 and 2 at the back of

counterclockwise movement switches the voltage at

the monitor receiver terminated in an external 600 ohm

A2TP5 to 0 Vdc.

line or a 600 ohm, 1 watt resistor, connect the rms

(11) The CARRIER LEVEL meter should read 0

voltmeter between TB1 terminals 1 and 2. The voltmeter

dB. If necessary, readjust SENSITIVITY control A3R7

will read 12.25 V 0.1 V. If the reading is not correct

for a 0 dB CARRIER LEVEL meter reading. Then adjust

adjust AUDIO LEVEL control A2R14 (fig. 2-1) to get

A2R52 (fig. 2-1) to get a +12 Vdc reading at A2TP5, to

12.25 V 0.1 V.

the point where any further counterclockwise movement

(27) Perform

the

maintenance

turn

of A2R52 switches the voltage at A2TP5 to 0 Vdc.

procedures of table 4-2.

4-11