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.
(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.
(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.
(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
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
(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
NORM indicator will go off
counterclockwise until the voltage at A2TP5 switches to
(24) Carefully adjust the RF TUNE control to get
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
of A2R52 switches the voltage at A2TP5 to 0 Vdc.
procedures of table 4-2.