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Page Title: Control Logic Board 2A1 Detailed Functional Operation
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TM 11-5820-873-34
respectively to the correct position for minimum
of the Reflected Power Amp develops logic 0 at U6A-1
reflected power  When reflected power has been
Gate 2A1U6A then establishes logic 1 at 2A1U6B-4 and
adjusted below the threshold, control logic board 2A1
2XA1-14, which is the 50 (+) output.  Gate 2A1U6B
ends the tune cycle The COUPLER STATUS READY
generates logic 0 at 2AIU6C-9 to reset the FF If RF is
Indicator is illuminated by a ground at 2A1-N and the
not present during a tuning cycle, the FF also resets but
AN/URC-92 is ready for transmitting
is set again by 2A1Q19 and 2A1U5C. The 50 Ohm FF
2-14. Control Logic Board 2A1 Detailed
is also set, and triggers 2A1Q14 if any of the following
Functional Operation
conditions occur the Time Delay running out or variable
inductor 2L4 reaching L max will set the FF thru
(Fig FO-6 and Fig FO-33)
2A1CR15 and/or 2A1CR16 respectively.  Also, some
frequency-impedance combinations may cause the FF
Board 2A1 provides control co-ordination for the
to reset and the tuner will not tune. This situation occurs
automatic tuning cycle The logic outputs of 2A1 provide
if reflected power rises above threshold during the same
initiation, cycling, completion and fault signals The
tune cycle Then an RC network, 2A1R29 and 2A1C36,
control logic board Is divided into eight functional blocks
charges to trigger 2AlQ13 Then 2A1Q13 established a
which will he discussed Individually The eight functions
logic 0 at 2A1U6D-13 to set the FF, 2A1U6D1 1, at logic
are Tune flip-flop, 50 ohm flip-flop, Fault flip-flop, Time
1 and trigger 2A1Q14 on. With that the 3 dB attenuator
Delay, C3-C6 control, Reflected Power Amp, RF
Is again switched in to prevent transmitting into a
Detector, and Lamp Driver
possible open or short circuit.
a. Tune Flip-Flop The Tune flip-flop is comprised of
2A1Q10, 2AlQ15, 2A1U3B-C-D, 2A1U4C-D and all
c. Fault Flip-Flop. The Fault FF consists of 2A1U4A-B,
related components When the unit is first turned on,
2A1U3B-6 is at a logic 0 due to circuit loading.
corresponding circuits When power is first applied
Depressing the TUNE START pushbutton on the
(transceiver turned on), circuit loading causes 2A1U4B-6
antenna coupler control (1A2) applied + 28 VDC to
to be logic 0 and set the FF The logic 1 at 2alU4A-3 Is
2XA1-A The +28 VDC turns on 2A1Q15, causing a logic
then fed to the Lamp Driver to light the COUPLER
0 at the collector, which initiates a tune cycle The logic 0
STATUS FAULT indicator. When the mode switch is
initiate signal resets 2AIU3C-8 causing a logic 1 at
set to CPLR TUNE KW, +10V is switched to 2XA1-2
2A1U3B-6 Because of this, 2AlQ10 turned on and
thru 2K1. The + 10V is applied to an RC network and
ground the Interlock (2XA1-7) which keys the transmitter
voltage regulator, in the Fault FF to generate a single
on in am The 2AlU: 3B-6 output is also fed to the Lamp
logic 1 pulse This pulse is inverted by 2A1U5D and the
Driver to light the COUPLER STATUS TUNING
logic 0 makes 2A1U4B-6 a logic 0 The logic 0 is also fed
Indicator The same logic 0 initiate signal is used in all
to Tune FF 2A1U3D-13 to extinguish the CPLR TUNE
the other functions except the [,amp l)river It also
READY indicator The output of 2A1U4A-3 is then at
provides the 2C1 home (2XA1-13) and 2I,L4 home
logic 1 and fed to the Lamp Driver to light the
(2XA1-R) outputs The Tune FF is reset, when the tune
COUPLER STATUS FAULT indicator The Fault FF is
cycle ends, by a logic 1 at 2AlU4C-9 from the Reflected
also set by a logic 0 from 2A1U5A-11. A logic 0 from
Power Amp which produces logic 0 at 2AlU4C-8 That
2A1U5A is caused when two conditions are met First,
logic 0 resets the Fault FF and the Tune FF which
the reflected power is above threshold and Reflected
extinguishes the COUPILER STATUS TUNNG Indicator
Power Amp 2A1Q3 causes a logic 1 at 2A1U5A-13.
At the same time 2A1U41)-11 is at a logic 1 which is fed
Second, Tune FF 2A1U3C-8 produces a logic 1 at
to the Lamp Driver to light the COUPLER STATUS
2A1U5A-12, indicating tuning is not in process  This
REAI)Y indicator
ensures. the COUPLER STATUS FAULT indicator will
light any time timing is required due to antenna or
frequency change If the Time Delay runs out, the Fault
b. 50 Ohm Flip-Flop The 50 Ohm FF includes
FF will he set with a logic 0 from 2A1CR20 to 2A1U4B-
2AlQ13,  2A1Q19  1A1U6A-B  C-D,  2A1U4C  and
associated components When a tune cycle is Initiated, a
Reflected  Power
logic 0 is placed at 2AlU6C-8 and sets the FF with a
2A101.2A1Q1, 2A1Q2, 2A1Q3.
2A1Q4, 2A1Q5,
logic 1 at 2AlU6D-11 The logic 1 triggers 2A1Q14 to
2A1CR1,  2A1CR2  and  associated  resistors  and
provide a ground, for energizing 2K4, at 2XA1-15
capacitors make up the Reflected Power Amp From
Energizing 2K4 switches the 3 dB attenuator in series
2X1A-3 a DC voltage, proportionate to reflected power
with the rf transmission line When reflected power drops
on the transmission line, is fed to 2A1U1-4. This signal
below threshold or RF power is not sensed by the RF
Is referenced to + 10 VDC and 2AlU1 develops its
Detector, the 50 Ohm FF is reset This causes 2A1Q14
output from that reference. The output at 2A1U1-10,
to cease conduction and 2K4 deenergizes, taking the 3
along with a gain input (2XA1-8) from the antenna
dB attenuator out of the transmission line If the reflected
power is below threshold, 2A1Q3

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