negative-pulse output of transformer T8601 (representing the leading edge of the comparator Q8601, Q8602 output) to armed
multivibrator Q8103, Q8104. In addition, a negative-pulse output from T8601 goes to diode CR8105. Resistors R8145 and
R8135 form a voltage divider and since they are of equal value, a positive 25-volt potential at their junction is applied to diode
CR8105, reverse-biasing it. Reverse-biasing the diode prevents the negative pulse from passing through CR8105 to trigger
the delayed-sweep gate multivibrator.
(3) You will notice that there is also a voltage divider (R8146, R8147) at the pulse-input side (cathode) of diode
CR8104. However, the value of R8147 is negligible compared to R8146, and the network produces a very small positive
voltage which the negative pulse can easily overcome to trigger the armed multivibrator. Capacitor C8122 shunts any
transient pulses that may be generated.
(4) In its quiescent state, Q8103 of the armed multivibrator is cut off and Q8104 is conducting. With Q8103 cut off, a
positive voltage (gate) is applied to armed lockout diode CR8102, reverse-biasing the diode. In this state, the diode prevents
any incoming trigger signals from firing the delayed-sweep gate multivibrator. At the same time, switching transistor Q8102
(zone D7) receives the positive output from the armed multivibrator and conducts heavily. When the switching transistor
conducts, SWP READY lamp DS8101 is shunted to ground, preventing the lamp from lighting.
(5) When the negative pulse output of transformer T8601 passes through diode CR8104, it triggers the armed
multivibrator, changing the operating state of the multivibrator. In this state, Q8103 conducts and Q8104 is cut off. Now
armed lockout diode CR8102 receives a negative voltage and becomes forward-biased. Forward-biasing the armed lockout
diode opens the trigger circuit, making it possible for the next trigger signal to fire the delayed-sweep gate multivibrator and
start the delayed sweep. The delayed sweep circuit as well as the strobe circuit operate in exactly the same way as described
in a above.
(6) In addition to forward-biasing diode CR8102, the negative-voltage output of the armed multivibrator cuts off
Figure 3-11. Armed-strobe node waveforms.
switching transistor Q8102. With the transistor cutoff, the SWP READY lamp is no longer shunted to ground and it lights.
This indicates that the delayed-sweep gate multivibrator is armed and will fire upon receiving the next trigger signal.
(10) Waveform 6 shows the negative turnoff trigger pulse, representing the differentiated trailing edge of the positive
gate from the normal-sweep gate multivibrator, after it passes through a differentiator and a diode. This negative pulse
(7) When the delayed-sweep gate multivibrator i triggered, it produces a negative-gate output at Q8107. The
triggers the delayed-sweep gate multivibrator, which in turn, deactivates the delayed sawtooth generator. The ramp output of
negative-gate is then differentiated by C8118, R8143 (zone D8) and the negative pulse, representing the leading edge of the
the delayed sweep generator that goes to the horizontal amplifier is shown by waveform 7. Waveform 8 shows the output of
gate, passes through diode CR8103 to trigger the armed multivibrator. When the armed multivibrator is triggered, it reverts to
the strobe circuit, which is activated by the positive-gate output of the delayed-sweep gate multivibrator.
its original operating condition.
(8) Let's briefly summarize the detailed description of the armed-strobe mode, using the waveforms in figure 3-11.
The first waveform shows the output of the normal sawtooth generator that goes to the horizontal amplifier and the
(1) In this mode only the delayed sweep is applied to the horizontal deflection amplifier, and the bright segment of the
comparator stage in the delay trigger pick-off circuit. Waveform 2 shows the inverted-differentiated output of the differentiating
CRT display in the armed-strobe mode now covers the entire screen. In addition, the strobe circuit is deactivated, so that the
amplifier, which triggers the armed multivibrator after passing through a pulse transformer and a diode. When the armed
signal displayed on the screen will have the same brightness as when the signal is displayed in the normal sweep mode. The
multivibrator fires, it produces a negative gate, shown in waveform 3, which forward-biases- (unlocks) the armed lockout
circuitry described in c above is also used in this mode except that the strobe circuit is now deactivated.
diode. This permits the next trigger to fire the delayed-sweep gate multivibrator.
(9) When the delayed-sweep gate fires, the negative-gate output, as shown by waveform 4, goes to the delayed
sweep Miller integrator via the disconnect diodes, and to the armed multivibrator via a differentiator network and a diode. The
The horizontal deflection amplifier operates in exactly the same way for all sweep modes (including the substitution of an
negative pulse of the differentiated signal, shown by waveform 5, triggers the armed multivibrator, reverting it to its initial state.
external signal source for the internally generated sweep signal). This circuit will be described for only two modes, normal
sweep and external sweep (X amplifier input).
a. Normal Sweep Amplification.
(1) With the DISPLAY LOGIC switch at NORM, the sawtooth output from the normal sweep generator (Miller
integrator V8203, V8204) passes through the switch to emitter follower Q8301 (zone A13). POSITION control R8306, R8307,
a dual-variable resistor, determines the point at which the sweep display appears on the CRT screen by controlling the
operating level of emitter follower Q8301. Emitter follower Q8304 provides a 23-volt operating level for Q8301.
(2) After passing through Q8301, the sawtooth signal goes to paraphase amplifier Q8302, Q8303. The paraphase
amplifier (common-emitter amplifier) produces two outputs, equal in amplitude and 180 degrees out of phase, from a single-
ended input (Q8301). With PULL X10 switch S830 in its normal position (pushed in), attenuator R8329, C8309 (zone B15)
with a ratio of 10 to 1, becomes part of the common-emitter circuit of the paraphase amplifier. This circuit reduces the