TM 9-6625-1753-14
C1
X10 amplifier, and the stages are bypassed. In the PULL X10 position of the switch, emitter follower Q207 with common
directly to the cathode of the CRT.
emitter amplifiers Q209 and Q211 (B12) compromise one series of amplifiers. Q208, Q210, and Q212 comprise a second
series which completes the push-pull amplifier. The outputs from the X10 amplifier or the bypass signal, as selected, are
3-11.3. Common Amplifier Section and CRT Termination Network
coupled to the switching amplifier through emitter followers Q801 and Q802.
a. General. At the output of the switching amplifiers, the signal from channel 2 joins the signal from channel 1 for
e. Channel 2. Channel 2 has an almost identical arrangement to channel 1. The CH2 input signal, attenuated by
amplification by one channel 1 for amplification by one channel of push-pull amplification by one channel of push-pull
attenuators which are selected by VOLTS/DIV switch S912 (D2) is push-pull amplified by two series of amplifiers (D7). With
amplification. This push-pull arrangement is continued through the CRT termination network, in the main frame, to the CRT.
the NORMAL-INVERT switch set to NORMAL and the PULL X10 switch closed, one series of amplifiers consists of V941,
The circuits include a delay circuit, a series of normal amplifiers, a differential amplifier, and the CRT termination network, as
Q401, Q404, and Q406, Q408, Q410, Q412, and Q902. The other series consists of V942, Q402, Q403, Q405, Q407, Q409,
discussed in b through e below.
Q411, and Q901. The NORMAL-INVERT and PULL X10 switches operate in the same manner as noted in c and d above.
DC BAL, VARIABLE, GAIN ADJ, and INVERT BAL controls are provided in the same circuit arrangement as was previously
b. Delay Circuit. Th selected signal (CH1, CH2, or both) is amplified by delay line drivers Q501 and Q502 (common
discussed. A channel 2 output signal (D11), and a signal used for channel 2 trigger separation, are taken from the output of
emitter amplifiers) and applied to delay line DL501. Delay line DL501 introduces a 185 nanosecond delay in the signal. This
the channel 2 preamplifier.
delay is provided so that the horizontal sweep may start before the applied signal, thus allowing the leading edge of signals to
be displayed. The signal is then applied through impedance Z501 to the following amplifier section; Z501 acts as an
impedance matching device to match the delay line to the following amplifier circuits. Since the delay line can introduce minor
3-11.2. Mode Selection
transients into the signal line, capacitor C501 and resistor R511 (both adjustable) are provided to minimize the effect of these
a. General. The mode selection circuits consist of emitter follower Q703 (a trigger coupling stage), oscillator Q704,
transients. R511 is normally adjusted to eliminate a dc shift, while C501 is adjusted to reduce any bumps which occur at the
switching multivibrator Q701 and Q702, switching amplifiers Q803, Q804, Q903, and Q904, MODE selection switch S709 and
end of the initial delay line operation.
the blanking pulse amplifier and trigger circuits. There are five possible modes (CH1, CH2, ALT, CHOP, and ADDED). These
modes are discussed in b through f below.
c. Amplifiers. A series of dc amplifiers consisting of common emitter amplifiers Q503 and Q505, with emitter follower
Q507, are balanced by Q504, Q506, and Q508. These two series of amplifiers comprise a push-pull amplifier group.
b. CH1 and CH2 Modes . In the CH1 mode, trigger oscillator Q704 (A14) is biased below cut-off by -50v applied through
S709-1F, while the input trigger to trigger amplifier Q703 is blocked by bias, due to the removal of +50v from the input network
d. Differential Amplifier. A two stage differential amplifier is provided. The input stage consists of Q512 and Q513 with
(see switch S970-1R). Forward bias is applied to Q701 through S709-1R (A16) and its conducts. With Q701 conducting
current regulator (constant current) transistor Q510. Output level adjust R545, and BEAM FINDER S950, set the normal
Q702 is cut-off (bistable multivibrator action). In this condition, diode CR801 is cut-off and switching amplifiers Q803 and
current for the input stage to the differential amplifier, and reduce this current to a very low level, respectively. If the BEAM
Q804 (C11) are allowed to conduct, while a positive voltage at the collector of Q702 is applied through CR901 to switching
FINDER switch is depressed when the CRT trace is off the screen, the trace will move to the edge of the screen. The second
amplifiers Q903 and Q904. The positive voltage (reverse bias) cuts off Q903 and Q904. Thus only the channel 1 signal is
stage (common base type) consists of Q511 and Q514 with Q509 acting as a voltage regulator to retain a constant base
amplified. In the CH2 mode, forward bias is removed from Q701 and applied to Q702 (A16). Therefore, Q702, and, in turn,
voltage for each amplifier. This differential amplifier reacts very strongly to signals of opposite polarity, while tending to null
Q903 and Q904 conduct, while Q803 and Q804 are cut off. In this state, only the channel 2 output is amplified.
out signals of the same polarity.
c. ALT Mode. In the ALT mode, the reverse bias on the input network for emitter follower Q703 (A13) is removed (see
e. CRT Termination Network . The CRT termination network acts as an impedance match between the CRT plates and
S970-1R), and the blanking trigger, applied through emitter follower Q703, reduces the bias on oscillator Q704. The oscillator
the differential amplifier. Low frequency peaking adjustment R65 and high frequency peaking adjustment C53 are provided.
operates, and the resultant trigger, coupled through T201, causes switching multivibrator Q701 and Q702 to pass through a
These controls are normally set to obtain the best possible reproduction of a square wave on the CRT.
half cycle. A second trigger completes a cycle for the switching multivibrator, and therefore the switching multivibrator, and
therefore the switching multivibrator and switching amplifiers change between channel 1 and channel 2 on alternate sweeps.
3-11.4. Internal Trigger Generation
d. Chop Mode. In the chop mode, the reverse bias for oscillator Q704 (A13) is removed (S709-1F) and the stage acts
a. General. The vertical amplifier provides facilities for developing a trigger. This trigger may be selected as the
as an oscillator. The switching rate is set at 100 kc or 1 mc by chop rate switch S971. For each cycle of oscillation from the
oscilloscope triggering source by setting the SOURCE switch on the delayed sweep plug-in unit to INT. When INT is
oscillator, a trigger is coupled tot he switching multivibrator, and the switching multivibrator controls the switching amplifiers as
selected, the composite signal (NORM) or the channel 2 (CH2 ONLY) signal may be selected by the TRIGGER switch, as
noted in b above.
indicated by b below.
e. ADDED Mode. In the ADDED mode, B+ is removed from the switching multivibrator (S709-1F-A15). With B+
b. Trigger selection and level adjustment . In the NORM position of the TRIGGER switch, the output from Q604 (D13) is
removed for the multivibrator, both sets of switching amplifiers (Q803, Q804, Q903, and Q904-A11 through D11) conduct, and
grounded by S960-2R, and only the output from Q610 appears at the base of Q606. In the CH2 ONLY position of the trigger
the output signal is the algebraic sum of the two input signals.
switch, the output from Q610 is grounded and only the signal from Q604 appears in the output. Since the input to Q610 is
grounded and only the signal from Q604 appears in the output. Since the input to Q610 is the composite signal from Q502,
f. Blanking Pulse Amplifier. To eliminate the transient which occurs when the vertical amplifier is switched from channel
while the input to Q604 appears in the output. Since the input to Q610 is the composite signal from Q502, while the input to
to channel, the CRT is blanked during trigger time. The blanking pulse developed by emitter follower Q706 (B17) is coupled
Q604 is the channel 2 signal from Q901, the composite signal or the channel 2 signal is selected. Each channel has a level
adjustment (R618 or R619) which effects the dc voltage regulator Q606 by controlling voltage regulator Q605. The
adjustments are set for a zero level dc output with no triggers applied.
3-6.1
