C1, TM 11-6625-821-45
The CONTROL TEST switch selects each of
the aircraft installation. The remaining im-
the control unit circuits and connects them,
pedance is simulated in Cable Assembly,
one at a time, to the CONTROL TEST ter-
Special Purpose, Electrical CX-11570/ARM-
minals. An external multimeter is connected
93, which connects the test set LOOP AN-
to the CONTROL TEST terminals to measure
TENNA connector J9 to the receiver.
the resistance of the selected control unit cir-
(1) The control information and power
cuit.
from the control unit in the test is
(1) To check the performance of the
applied to the receiver through RE-
tunning synchro in the control unit,
CEIVER-CONTROL switch S4.
switch S4D connects the synchro to
(2) An external power source supplies
the BEARING INDICATOR. The
27.5-volt direct current (de) to the
position of the tunning synchro can
test set. DC indicator lamp DS1
then be read directly from the BEAR-
lights when the dc voltage is present.
ING INDICATOR.
The 27.5 volts dc is applied to the in-
(2) When checking the control unit, the
verter, which converts the de voltage
into 26 volts, 400 cycles per second
inverter supplies the required alter-
(cps). The inverter applies its out-
nating current (ac) power. Since the
put to the control unit, which routes
control unit is checked without a
receiver, switch S4B switches in the
the 26 volts, 400 cps to the receiver
inverter load to replace the load the
through switch S4. Ac indicator con-
receiver normally places on the in-
trol Q1 receives the 26 volts, 400 cps
verter.
from the control unit and lights AC
indicator lamp DS2.
d. Inverter. When checking the performance
(3) Switch S4D connects the output sig-
of the inverter, the test set supplies the same
nal of the receiver to the BEARING
de voltage and load that is applied during
INDICATOR on the test set. This in-
normal operation of the inverter. The perform-
dicator indicates the receiver's re-
ance of the inverter is then checked with the
sponse to the simulated signals from
external test equipment.
the test set.
e. Loop Test Fixture. The loop test fixture
c. Control Unit. The test set checks the
is used as an aid to measure the Q of the two
performance of the control unit by providing
pairs of coils in the fixed loop antenna. When
resistance checks and indicating the position
in use, the loop test fixture is installed between
of the tuning synchro. Switch S4B applies
the fixed loop antenna and a Q-meter. Each
ground to one-half of the circuitry in the con-
pair of coils in the fixed loop antenna is applied
trol unit. The other half of the circuitry is
to the input of the loop test fixture. The loop
connected through the RECEIVER-CON-
test fixture selects one of the pairs of coils and
TROL switch to CONTROL TEST switch S3.
connects it to the Q-meter.
Section II. Detailed Function of Test Set, Direction Finder Set
AN/ARM-93
check the receiver, and the control unit section
13. General
is used to check the control unit. RECEIVER-
The functional portion of the test set is
CONTROL switch S4 selecs the section of the
divided into a receiver section and a control
unit section. The receiver section is used to
test.
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