The input signal is attenuated through R617 and the input
R672 (Vert Gain adjustment) in series with R671, to the
impedance to Q620, so that an approximate 5 division dis-
emitter of Q660. Gain of the amplifier is a function of the
play in the LIN position will provide approximately the
ratio Rf/ Rin. Rf is controlled by the Vert Gain adjustment.
same signal amplitude when the switch is changed to either
POSITION control R665, sets the input DC level to the
of the other two positions.
operational amplifier which is reflected as a DC shift in
In the SQ LAW position the signal is applied through two
the output level to the vertical output amplifiers. Diodes
D670 and D671 do not normally conduct They limit the
germanium diodes, D612-D613, to the base of Q620. The
overdrive and speed up the recovery of the amplifier.
diodes are connected back to back to form a square-law
voltage divider. Signal voltage to the amplifier Q260 in the
The low impedance signal output from the operational
SQ LAW mode becomes a function of the diode's dynomic
amplifier drives the vertical amplifier output stage. The
resistance as shown in Fig. 3-11.
output amplifier is connected as a paraphase amplifier to
convert the single-ended input signal to a push-pull drive
Note that diode resistance exceeds 100 k - for very low
for the vertical deflection plates of the CRT, The common
(mV) input signals. The divider ratio is approximately 200:1
emitters of the output amplifer are connected to a constant
so 0.5% of the signal will be applied to Q620. With a 150
current source Q690, which supplies approximately 2.5 mA
mV signal the dynamic resistance of the diode decreases to
to each output side of the amplifier (or 5 MA total).
approximately 5 k , so approximately 10% of the signal
will be applied to Q620. The circuit will normally have about
70 mV signal for full screen display so the diodes operate
along the steep portion of the dynamic resistance curve.
Trigger Generator, Sweep Generator and
This no-linear dynamic resistance of the divider produces
Horizontal Amplifier
a display which emphasizes small signal level differences
between signals. The vertical response for the SQ LAW
The sweep generator will free run or it may be triggered
display is approximately proportional to the signal power.
by the internal video signal, the line frequency or an external-
ly applied triggering signal.
Q620 is a high gain amplifier driving the complementary
Sweep rates in a 1-2-5 sequence may be selected for
amplifier Q630-Q631. The complementary amplifier provides
the drive for the step-up transformer T640. This provides
0.5 s/div to 10 s/div. The sweep voltage generated by the
sweep generator is amplified by the horizontal amplifier and
the voltage gain required to drive the LIN detector, the log
circuit, the recorder and the intensifier circuit. The signal
applied as a push-pull sawtooth to the horizontal deflection
to the RECORDER output connector is a linear signal in the
plates of the CRT.
LIN and LOG positions of the VERTICAL DISPLAY switch,
If the sweep generator
triggered, the selected trigger
IS
and square law in the SQ LAW position.
signal is amplified and shaped by a trigger amplifier then
The video detector diodes D640 and D641 are connected
applied to the trigger generator. Trigger signal level and
as a voltage doubler for maximum efficiency The output
slope can be adjusted and selected.
video signal is then amplified through the emitter followers
The trigger pulse from the trigger generator switches
Q640 and Q641 and applied through the VERTICAL DIS-
a sweep gating multivibrator to generate the unblinking gate
PLAY switch SW600 to the vertical amplifier. Q641 is long-
for the CRT during sweep time and initiates the operation of
tailed through R657 to the -10 V supply to provide a constant
the sweep generating circuit.
DC output level to drive the vertical amplifier, the baseline
suppress circuit and the RECORDER output connector. This
The sweep generator supplies a linear and timed ramp
provides minimum baseline shift when the VERTICAL DIS-
signal to the horizontal amplifier plus a feed-back signal
PLAY selector is switched between positions.
to the trigger generator. This feed-back signal locks out
or holds off the trigger signals to the sweep gating multi-
The logarithmic circuit consisting of R650, R651, R653, D650
vibrator until the sweep has run and the circuit is ready
and D652 provides a logarithmic display when the VERTICAL
again to be triggered.
DISPLAY switch is in the LOG position.
Trigger Generator. The selected trigger signals from the
Low amplitude video signal voltages appear across D650
SOURCE siwtch are AC coupled through C701 to an opera-
with little or no attenuation. As the amplitude increases,
tional amplifier Q700, Q710 and Q720. The output of this
the current through the diode becomes an exponential
operational amplifier is a low impedance signal that drives
function of the voltage across the diode, R650 becomes the
one side of a comparator amplifier Q730-Q731.
current source for the diode, so the voltage out becomes a
logarithmic function. As the signal amplitude incrases the
The input DC level to the operational amplifier is set
diode current approaches the linear region of the voltage-
by the trigger LEVEL control R702, and the Trig Level Center
current characteristic curve; however, this current through
adjustment R724. This input DC level to the operational
R653 develops sufficient voltage across D652 to turn this
amplifier also governs the output DC level of the amplifier
diode on and the two diodes operate in series to extend the
which is the input level to the comparator Q730-Q731,
logarithmic range of the circuit.
One side of the comparator is referenced through the
SLOPE switch SW720 to ground, while the other side is
Vertical Amplifier.
The vertical amplifier consists of
connected through the SLOPE switch to the output of the
an operational amplifier driving a paraphase output am-
operational amplifier. The Trigger LEVEL control adjust the
plifier. The operational amplifier consists of the grounded
DC level, on the signal side of the comparator, to a voltage
base amplifier Q660, driving the emitter follower Q670 and
potential above or below ground. The input trigger signal
the inverter amplifier Q680. Output signal from the collector
must overcome this unbalance to trigger the trigger generator
of Q680 is fed back to the input of the amplifier, through
3-12
