TM 11-5840-281-35/1
of operated relay K4501, control R4520, resistor R4517,
loop. The phase-lag network serves to stabilize the loop
and diode CR4505. The reduced series resistance
and prevent oscillations. The positive signal at the plate
allows the integrating capacitor to charge more quickly to
of tube V1605A is coupled through capacitor C1611 to
the potential which creates the sweep feedback voltage
the grid of cathode follower tube V1605B. The cathode
necessary to fire the gate shutoff circuit. Consequently,
of tube V1605B is dc-coupled to the grids of power
in the 20-mile precision mode, the sawtooth terminates
amplifier tubes V1606 and V1607; consequently, the
at approximately 300 sec, rather than at 600 sec as in
quiescent current flow through V1606B establishes the
bias on the power amplifiers. If the between-sweep bias
the search mode. Control R4520 controls the slope of
on the power amplifiers was at some point above cutoff,
the sawtooth waveform and is adjusted so that the 20-
current would flow through the deflection coils between
mile range mark appears approximately one-inch in from
sweeps and result in the time-base sweep originating
the right edge of the crt in the 20-mile range.
slightly off-center on the crt. This would appear as a hole
(10) In the 5and 10-mile ranges of precision
in the center of the ppi display; however, if the between-
operation, the charging path consisting of diode CR4506,
sweep bias on the power amplifiers was below cutoff, the
first portion of the sweep sawtooth would be lost. The
CR4505 is inserted in series with the integrating
result would be a shortened time-base sweep. Zener
capacitors by means of RANGE MILES switch S1101.
diode CR1603 establishes the bias on tube V1605B,
Also, the sweep feedback voltage coupled through
which in turn sets the bias on tubes V1606 and V1607
capacitor C4503 is disconnected, producing an
right at cutoff. Clamp diode CR1602 prevents the grid of
exponentially-curved sawtooth waveform.
The
tube V1605B from going more negative than the bias
exponentially-curved sawtooth results in a display that
established by diode CR1603
has the form of an expanded time-base sweep at the
(2) Parallel connected power amplifier
start (left) of the presentation and a compressed time-
tubes V1606 and V1607 have the rotating deflection coil
base sweep near the end (right). The range marks are
as a common plate load. When the positive sawtooth
therefore spaced logarithmically and the more critical
sweep voltage appears at the grids, the power amplifiers
close ranges occupy a greater distance along the sweep.
conduct and a sawtooth current through the deflection
Control R4521 is adjusted so the 10-mile range mark
coil is produced. The sawtooth current through the
appears approximately one-half inch in from the right
deflection coil produces a linearly increasing magnetic
edge of the crt in the 10-mile range. The output of the
field which pulls the electron beam across the face of the
sawtooth generator is taken at terminal F of connector
crt. The feedback loop between tubes V1606, V1607,
P1450 and applied to the grid of tube V1604 on the
and V1604 causes the current waveform through the
rotating coil amplifier subassembly in the indicator
deflection coils to have the same shape as the time-base
subsection.
sweep voltage waveform at the input of tube V1604.
d. Rotating Coil Amplifier Circuit (fig. 7-11 and
This compensates for any distortion introduced by any
7-47). The rotating coil amplifier operates as a linear
nonlinear circuit components The positive sawtooth
sweep amplifier that performs two functions: first, it
voltage developed across parallel cathode resistors
amplifies the step-sawtooth sweep signal from the sweep
R1626 and R1634 is tapped off as the sweep feedback
generator in the sweep generating circuit and converts it
voltage. Unregulated +450 volts is applied to series
to a current waveform of sufficient amplitude to drive the
regulator tube V1601 which supplies a regulated + 300
deflection coils on the indicator crt, and second, it
volts at the cathode output. With an increase in the plate
provides a sweep feedback voltage.
voltage of tube V1602B, cathode voltage of tube V1601
(1) The positive step-sawtooth from the
will tend to increase. Reference tube V1603 establishes
sweep generator subassembly is applied to the grid of
the grid bias for amplifier tube V1602B. Any increase in
amplifier tube V1604. A negative signal is developed at
the plate voltage of tube V1602B is applied to the grid of
the plate and coupled through capacitor C1609 to the
tube V1602A and causes the plate voltage of tube
input of amplifier tube V1605A. Capacitor C1610 and
V1602A and the grid voltage of tube V1602A and the grid
resistor R1632, and the parallel resistance of resistor
voltage of V1601 to decrease. In this manner, the
R1616 and tube V1604, form a phase-lag network.
internal
Since negative feedback is applied to the cathode of
tube V1604, the rotating coil amplifier acts as a closed
2-42
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