TM
11-6625-928-35
CHAPTER 2
CIRCUIT FUNCTIONING
2-1. General
quency (RF) load. The RF antenna connector of
the radio set under teat should be connected through
The MK-994/AR, in conjunction with standard test
cable W12 to T/R ANTENNA connector J11 to
equipments, provides the capability for testing and
properly load the antenna circuit when transmit-
performing checkout and/or repair of the electronic
receive (tr) relay K1 is energized. With tr relay K1
equipment that constitutes the SLAE and the ARC-
164(V). In addition to this equipment, Test Facilities
deenergized, the test signal, which is applied through
Kit MK-994A/AR provides the capability to test the
cable W15 to SIGNAL INPUT connector J12, is
RT-1300/ARC-186(V),
RT-1354/ARC-186(V),
connected through connector P4, coaxial adapters
C-10604(V)/ARC-186(V), C-10606(V)/ARC-186(V),
CP1 (9.5 decibels (db)), CP6, CP7, attenuator AT5
CM-482/ARC-186(V), and CM-492/ARC-186(V).
(12 db), connector P5, closed contacts B3 and B2 of
Communication System Control C-6533/ARC and
tr relay K1, T/R ANTENNA connector J11, and
Heading-Radio Bearing Indicator ID- 135 l/A are
cable W12 to the radio set under test (fig. 2-1 and
major units of the maintenance kit. For detailed infor-
3-9). RADIO ANTENNA FUNCTION switch S1
mation on these two major units, refer to the appli-
cable technical manual (app. A). The direct current
homing capability of the radio set under test is being
(dc) power distribution is common to all test circuits
checked. RADIO TEST switch S2 provides selection
and is discussed in paragraph 2-2.
of the circuit function to be tested.
2-2. Dc Power Distribution
TEST INPUT connector J17 (E, fig. 5-2), provides
The dc power (+28-volt) distribution within the
audio signals. With RADIO TEST switch S2 set to
maintenance kit is shown in figure 5-1. The dc power
4, the audio signals are applied to the audio circuits
is applied to the maintenance kit at front panel DC
in the radio set under test through RADIO TEST
POWER connector J28-A. The +28 volts is then
INPUT connector J17, switch S2A and RADIO
applied through 10.0-ampere DC POWER circuit
SET NO. 1 connector J1-Y. Audio from the radio
breaker CB2 to terminal board TB2-4. Jumpers on
set under test is applied to maintenance kit Com-
terminal board TB2 connect the +28 volts at
munication System Control C-6533/ARC (COMM
TB2-4 to TB2-1, 2, 3, and 5 for application to points
CONT NO. 1) through RADIO SET NO. 1 con-
within the maintenance kit. The +28 volts at
nector J1-d (C, fig. 52), terminal board TB1-4,
terminal board TB2-4 is also applied to DC POWER
TBI-5 and COMM CONT NO. 1 connectors J1-
indicator light DS3 as a front panel indication of dc
KK, MM, PP, SS, and UU, The audio signal is
power presence. The +28-volt return at DC POWER
controlled by COMM CONT NO. 1 switching cir-
connector J28-B is connected to terminal board
cuits and amplified by the headset amplifier. The
TB3-1. Jumpers at terminal boards TB3-1 through
amplified audio is applied through COMM CONT
TB3-6 provide ground points for maintenance kit
NO. 1 connectors J1-TT and XX, HEADSETS 1
connectors J15-B and D, and cable W20 or W21 to
Headset-Microphone H-101A/U to provide aural
2-3. Radio Test Circuit Analysis
monitoring of audio signal.
a. Radio tests are perfO rmed with the
radio set
to TRANSMIT, a ground at COMM CONT No. 1
being tested connected to RADIO SET NO. 1 con-
connector J1-K is applied to terminal X2 of trans-
mit-receive (tr) relay K1. With RADIO ANTENNA
FUNCTION switch S1 set to XCVR, +28 volts is
kit. A selected am or fm generator, connected
applied through switch S1, energizing relay K1.
through cable W15 to SIGNAL INPUT connector
With RADIO TEST switch S2 set to 4, relay K1 can
J12 provides a test signal. A wattmeter connected
also be energized by application of a ground (retrans-
between POWER METER OUTPUT connector
mit control input) through switch S2. When relay
J9 and POWER METER INPUT connector J10
K1 is energized, a ground is applied from TB3-3
provides for measuring transmitter power. Electrical
through terminals Al and A2 of relay K1 to TB4-4.
51-ohm dummy load AT1 provides the radiofre-
This ground is applied to RADIO SET NO. 1 con-
2-1
Change 8
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