(d)
Hysteresis
Adjustment. The hysteresis adjust-
ment
(R2245) sets the
difference
in the trigger threshold
and the
arm threshold. The closer the levels
are to
each
other,
the more susceptible the circuit
will be
to
triggering
on noise.
If
the
levels are
too
far apart, the
circuit will re-
quire
excessive input signal amplitude
to
generate
a
sweep
gate.
(e) Trigger View Pickoff.
A sample of the
trigger
input signal is supplied to pins
10
and
1 1 of
U2260.
This
paraphase signal passes through emitter followers Q2350
and Q2356
to
the TRIG
VIEW
switch
(S4380). When the
TRIG
VIEW
switch is pushed, the signal
from the Delay
Line Driver
is
disconnected from the
Delay Line and the
trigger view signal is connected in its
place.
(3)
B Trigger
Generator.
The B Trigger
Generator
operates in the
same manner
as the A
Trigger
Generator
ex-
cept in the STARTS AFTER
DELAY
position
of the
HORIZ
DISPLAY
switch. In the
STARTS AFTER
DE-
LAY
mode,
^5
volts is
connected
to pin
2
of
U2160
through
S2100 and
S2650 (see Figure
4-5).
This discon-
nects the trigger
signal from
point
B, sets
point D LO,
and
sets point
C
HI.
At
the
end
of holdoff,
point E
goes
LO causing point F
to go
HI.
This
sets point
K LO and,
because of the
HI always
present
on point
C,
causes
a
sweep
gate
to
be
generated.
(4)
A Sweep Generator.
A
sweep generator con-
sists of U2790
and
associated circuitry.
Figure FO-6 shows
a complete
schematic
diagram of the circuit.
Figure
4-6
shows
a
simplified diagram of the
circuit.
Figure
4-7
shows
the
waveforms produced during A sweep generation.
(a) Sweep
Generator Integrated
Circuits. Both the
A
and
B Sweep Generator
integrated
circuits (U2790 and
U2690 respectively)
are
the
same. However,
the functions
of some
of the pins are different.
The following
lists the pin
numbers
and their
functions:
1
Pin
1 is the input for
the DELAY TIME
POS
control.
This pin is
only used
in the A
Sweep
Gener-
ator.
When
the A ramp on pin
2 is equal
to
the voltage
on pin
1,
a
delayed
gate is produced
at
pin
16.
2
^
Pin
2 is the input for
the ramp
voltage from
the
output
Miller circuit.
This voltage
is internally
con-
nected
to pin
5
when
pin 7 is
LO.
^Pin
3 sets
internal
current
levels.
2
Pin
4 sets
the Miller
null and
retrace
currents
for
the
A
Sweep
Generator
only.
This function
is per-
formed
by
another
circuit
in the
B Sweep
Generator.
AIR
FORCE
T033A1-13-496-1
NAVELEX
0969-LP-170-0010
Operation
Instructions
5
Pin
5 is
the sweep ramp
output. The
ramp
at
pin
5
is connected
to
the Horizontal Preamplifier.
Pin
5
is switched on or off
by
the voltage on pin
7.
»
^
Pin
6
sets the internal current
levels
which,
along with R2682 or R2782, determine
the sweep
start
voltage.
2
Pin
7 controls the sweep
ramp output
at
pin
5. When pin 7
is LO
the sweep
ramp
at
pin
2 is internally
connected
to pin
5.
When pin
7 is HI, the sweep
ramp
at
pin
2 is
disconnected
from pin
5
and pin
5
is set
to
—5
volts.
^Pin
8 is the connection for
the
—5
volt
supply.
_9
Pin
9 is the ground
connection.
10 In the A sweep Generator,
pin
10
produces
an
output which
initiates holdoff. In the
B Sweep
Gener-
ator,
pin
10
produces an output
which is supplied
to
the
-i-B
GATE
OUT Amplifier
in the Main
Module.
1
1
The voltage
connected
to pin 1
1 sets the
amplitude
of the unblanking
signal
at pin 12.
_12
The
signal
at
pin
12 is
supplied
to the Z
Axis Amplifier in
the Main Module
to
unblank
the
crt.
The
amplitude
of this signal,
and therefore
the
brightness
of
the
crt display,
is controlled
by the
voltage on
pin
11.
13 Pins
13 and 14 work
together.
A
HI
on
either pin
prevents
sweep generation.
Both must
be
LO to
start sweep generation.
In
the
A
Sweep
Generator,
pin
13
is held
LO through
a
resistor
to
ground
and only
pin
14
controls sweep
generation.
In
the B
Sweep
Generator
pin
14
goes
LO when the
A Sweep
Generator
starts
but pin
13
doesn't
go LO until
the B Trigger
Generator
produces
a
sweep
gate. In
the STARTS
AFTER
DELAY
position
of
the
B SOURCE switch,
a B sweep
gate
is produced
as soon
as pin
16 of
U2790
produces
a delayed
gate.
In
other
settings,
a B sweep
gate
is
produced
when the
first
ade-
quate trigger
signal
occurs after
a
delayed
gate
is
produced
at pin
16 of
U2790.
14 Pin
14
works
with pin
13.
See the
pin
13
discussion.
1
5
Pin
15 is the
connection
for the
-t-5
volt
supply.
16
Pin
16
of
the A Sweep Generator produces
a
delayed gate to remove the holdoff condition from
the B
Trigger Generator. This
output
is produced when
the A
ramp voltage on pin 2 reaches
the
dc
level
on pin
1.
4-13
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