TM 11-5840-281-35/1
resistance of tube V1601 is corrected continuously,
sweep gate input from the sweep generator is inverted
maintaining a regulated +300v output.
by transistor Q2701 and applied through a differentiator
network to the cursor gate multivibrator. The output of
the multivibrator is a negative 500-sec gate which is
2-9.
Cursor Generator Circuit Description
(fig. 7-12)
applied to the reference and cursor sawtooth generator
circuits. When the cursor ends, the collector of transistor
a. General. The cursor generator circuits
Q2702 returns from a positive voltage to 0 volt.
function as part of the control-indicator section to
Transistor Q2713, and diodes CR2707, CR2708
produce the cursor pulse which is mixed with the
conduct, and the sawtooth comparator, the cursor trigger
touchdown markers and range marks before being
generator (transistors Q2707 and Q2708), and the cutoff
routed to Control-Indicator C-6988/TPN-18 for display as
generator (transistors Q2711 and Q2712) are inhibited
markers on the crt. In doing so, these circuits utilize the
until the next sweep gate arrives.
sawtooth generator, sawtooth comparator, and part of
c. Reference Sawtooth Generator Circuit (fig
the cursor control and cursor generator subassemblies.
7-12 and 7-55). The input to the circuit is the cursor
(1) The sweep gate from the sweep
sawtooth gate from the sawtooth comparator circuit.
generator subassembly triggers amplifier Q1 of the
(1) The reference sawtooth generator
cursor gate circuit. The cursor gate circuit produces a
consists of gate transistor Q2601; clamp transistor
500-esec gate to initiate the cursor pulse generator
Q2602; sawtooth generator transistors Q2603, Q2604,
output.
The reference sawtooth generator circuit
and Q2605; and emitter-follower transistor Q2606 on the
generates a fixed slope sawtooth for comparison with
sawtooth generator subassembly.
Gate transistor
variable level sawtooth signals developed in the cursor
Q2601 and clamp transistor Q2602 produce a gate for
trigger generator and fill-in sawtooth generator circuit.
the reference sawtooth generator which consists of
The cursor sawtooth generator circuit generates a
current-adder transistor Q2603,
temperature-
sawtooth signal whose slope is determined by the sum of
compensating
transistor Q2604, emitter-follower
cursor angle no. 1 and cursor angle no. 2 currents. The
transistor Q2605, and associated components.
(2) In the quiescent state of the reference
cursor sawtooth slope proportional to the instantaneous
sawtooth generator, transistor Q2602 conducts lightly
antenna scan angle with respect to the courseline or
and clamps the junction of resistor R2610 and capacitor
glideslope cursor to be generated.
C2602 at approximately + 1.4 to 1.5 volts. Transistor
(2) The cursor trigger generator circuit
Q2601 cuts off when the negative 500-psec cursor
compares the fixed-slope reference sawtooth signal with
sawtooth gate is applied to its base. This allows the
the variable-slope cursor sawtooth signal to develop a
base of clamp transistor Q2602 to go positive and Q2602
cursor trigger pulse. The fill-in sawtooth generator circuit
cuts off. Normally, capacitor C2602 would now charge
is basically the same as the cursor sawtooth generator
positive through resistor R2610 up to the +E reference
circuit except that cursor pulse termination data, rather
voltage (approximately 30 volts); however, current adder
than start information, is generated. The cursor trigger
transistor Q2603 conducts relatively heavy through
cutoff generator circuit develops a variable timeshifted
resistor R2610 and drops the voltage at the junction of
pulse used as fill-in for the cursor trigger pulse and is
resistor R2610 and capacitor C2602 to a value of a few
displayed a solid cursor on the crt. The cursor pulse
tenths of a volt. The exact amount of current transistor
generator circuit supplies a positive cursor pulse to the
Q2603 conducts through resistor R2610 for a given
mixer amplifier on Control-Indicator C-6988/TPN-18.
emitterbase bias is determined by REF SAW SLOPE
The cursor pulse is terminated by the negative cursor
control R2609. When clamp transistor Q2602 is cut off
trigger cutoff pulse from the cursor trigger cutoff
by the cursor sawtooth gate, capacitor C2602 begins to
generator circuit.
charge exponentially to the voltage at the junction of
b. Cursor Gate Circuit (fig. 7-12 and 7-56)
resistor R2610 and C2602. The positive charge across
The cursor gate consists of amplifier transistor Q2701,
capacitor C2602 is coupled to the base of emitter-
and monostable multivibrator transistors Q2702 and
follower transistor Q2605,
Q2703 on the sawtooth comparator assembly. The
2-43
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