Operating instructions

Gate Generator
The Gate Generator stage provides
an auto enable gate to
the Logic circuits (diagram 3), and a sweep start gate and
Z-axis gate (unblanking) to the Sweep Generator circuit
(diagram 4) . Refer to Figure 3-4 for a timing diagram of the
Gate Generator functions .
When an adequate trigger signal is applied to U85-pins 13
and 14, a HI level is produced at U85-pin 3 and a LO level
is produced at U85-pin 4 .
The HI level from U85-pin 3 is coupled through emitter
follower Q88 and J200-2 into the Logic circuit (diagram 3)
to indicate that a triggering signal has been received . The
Logic circuit (diagram 3) sets the auto sense at J200-3 H I,
turning off Q98 . Simultaneously, the LO level at U85-pin 4
gates comparator Q96-Q92 . The collector of Q92 rises HI
to provide a sweep start gate at J200-5 and the collector of
Q96 falls LO to provide a Z-axis gate (unblanking) at
J200-4 .
GATE
U85 PIN 3
GATE
U85 PIN 4
AUTO MODE OPERATION
WITH TRIGGER SIGNAL
u
AUTOMODE OPERATION
WITHOUT TRIGGER SIGNAL
1986-63
Sweep Modes
Fig . 3-4 . Timing diagram for Gate Generator stage (092, Q96,
098) .
LOGIC
O3
Theory of Operation-71380
In the absense of a trigger output at U85-pins 13 and 14,
pin 3 is set LO and pin 4 is set HI . The LO level from U85-
pin 3 is coupled through J200-2 to the Logic circuit (dia-
gram 3) to indicate the lack of a triggering signal . The Logic
circuit provides a LO-level auto sense pulse through J200-3
to
the
base of Q98 . This LO level gates the comparator
(Q98 and
Q96) .
The
collector of Q98 rises high to provide a
sweep start gate and the collector of 096 falls LO to pro-
vide
a Z-axis gate (unblanking) at J200-4 .
The Logic circuit
controls the sweep modes and associated
functions
of
the
time-base unit (e .g ., sweep display, hold
off,
auto
sweep,
single sweep, etc .) . The Logic circuit also
generates
control signals for the mainframe . A block dia-
gram for the
Logic circuit is shown in Figure 3-5 .
Integrated
circuit U220 controls the NORM, AUTO, and
SINGLE SWEEP MODES
and also generates control signals
used in the 71380 . P-P AUTO
operation is described in the
Trigger Generator circuit description (diagram 2) .
3- 9
AUTO ENABLE
GATE
J200-2
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AUTO
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J200-3
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Z-AXIS GATE
J200-4
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SWEEPSTART
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GATE
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J200-5
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0
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