Circuit Description—475
Pin 2. This is the negative Auto Sense Input. A fixed DC
level established by R602 and R603 is connected here.
Pin 3. This is the + auto gate terminal. In the AUTO
mode of operation, if no trigger signals are applied to pin 1
of U600 during the ^40 ms time period following the end
of holdoff, the gate level at pin 3 steps LO to turn Q574
on, which initiates a sweep.
Pin 4. This is the — auto gate terminal, not used in this
application.
Pin 5. Input terminal for negative voltage supply.
Pin 6. This is the auto gate timing terminal. R609 and
C609 determine the amount of time between the end of
holdoff and the generation of the auto gate.
Pin 7. This terminal lights the TRIG'D light when a
triggering gate has occurred.
Pin 8. This is the holdoff timing terminal. The time
between the end of a sweep and when a positive pulse is
conducted at pin 8 is determined by RC components
(selected by the TIM E/D IV Switch) in the Holdoff Timing
circuit.
Pin 9. Ground terminal.
Pin 10. Not used in this application.
Pin 11. This terminal lights the READY light when
operating in the single sweep mode.
Pin 12. This is the single sweep mode terminal. When +5
volts is connected to this terminal, the sweep operates in
the single sweep mode; when the terminal is left open or
grounded, the sweep operates in the repetitive mode.
Pin 13. Not used in this application.
Pins 14 and 15. Single sweep reset terminals. Pushing the
PUSH TO RESET button prepares the single sweep
circuitry to respond to the next one triggering event. Also
causes the READY light to be lit.
Pin 16. This is the holdoff start input terminal. The HI
sweep reset gate pulse from the Holdoff Start circuit is
applied here to initiate sweep holdoff.
Pin 17. This is the holdoff output terminal. The gate
level at this terminal is HI during holdoff and LO otherwise.
Pin 18. Sweep disable input. +5 volts applied to this
terminal disables all sweep action.
Pin 19. Auto mode terminal. Grounding this terminal
enables auto sweep operation.
Pin 20. Input terminal for positive voltage supply.
Main Gate Comparator
Q572 and Q574 form the Main Gate Comparator and are
connected as a voltage comparator, where both transistors
do not conduct at the same time. The input signal to the
stage is the positive-going trigger signal from the A Fire
Trigger TD in the A Trigger Generator circuit. The signal at
the collector of Q574 is inverted by Q588, is connected to
the Z Axis Logic Multivibrator to control CRT blanking,
and to Q584 to generate the A + GATE output signal. The
signal at the collector of Q574 connects to the base of the
Main Gate Amplifier stage (Q902) in the Sweep Generators
circuit to initiate sweep generation.
Delayed Gate Comparator
Q802 and Q804 form the Delayed Gate Comparator and
are connected as a voltage comparator where both transis
tors do not conduct at the same time. The input signal to
the stage is the positive-going trigger signal from the B Fire
Trigger TD in the B Trigger Generator circuit. The signal at
the collector of Q804 is inverted by Q826 and is connected
to the Z Axis Logic Multivibrator to control CRT blanking
and to Q824 to generate the B + GATE output signal. The
signal at the collector of Q802 connects to the base of the
Delayed Gate Amplifier stage (Q996) in the Sweep Genera
tors circuit to initiate sweep generation.
A Trigger TD Reset Circuit
Q612 and Q628 are connected as a voltage comparator
and form the A Trigger TD Reset Circuit. At the start of
holdoff, pin 17 of U600 steps HI. This turns on Q612 and
turns Q628 off. The collector signal of Q612 connects to
the Trigger Tunnel Diodes in the A Trigger Generator
circuit and resets them to their LO state. A t the end of
holdoff pin 17 of U600 steps LO, Q612 turns off, and
Q628 turns on.
Holdoff Start Circuit
Q594 and Q596 form the Holdoff Start Circuit. The
input signal to the stage is the positive-going end-of-sweep
signal from the Sweep Generators circuit or from the
3-10
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