AIR
FORCE T033A1
-13-496-1
NAVELEX 0969-LP-1
70-0010
Operation Instructions
7
End of Retrace.
When the
retrace ramp
on
pin
2
of U2690
reaches about
+2
volts, the
emitter of
Q2636
(through
the emitter
of
Q2632)
is
pulled suffi-
ciently
positive
to
forward bias
Q2636. At the same
time,
the
emitter
of Q2629
becomes
sufficiently positive to
turn
off Q2629.
The
initial condition
(before
B
delayed
gate
generation) is
restored.
The collector of
Q2636
goes less
negative, decreasing
the forward bias on
Q2624. Now
Q2624
supplies just
enough
current
through
Q2620
and
Rt
to
hold the
inverting and
non-inverting inputs
of the
B
Miller op
amp
at
the
same voltage.
(b)
Sequence
of Events During B Sweep
Gener-
ation
in
MIXED Mode.
In the MIXED
mode, B
sweep
gen-
eration is
similar
to
that
in the
A
INTEN
or B
DLY'D
modes.
The main
difference is that the voltage
level on pin
2 of
U2690
is
controlled
by
the A sweep ramp
before a B
sweep gate
is generated. Also, a
HI is placed on pin 7 of
U2790
causing pin 5
of
U2790 to go LO
and disconnect
the
A
ramp from the
Horizontal Preamplifier.
1
Before
A Sweep
Starts. When the
MIXED
button is pushed,
the
A
sweep ramp is connected
to
the
base
of Q2636 through R2637 and R2781
.
Ideally
the
A
and
B
sweep start voltages will be about
the
same,
causing
both Q2636
and Q2632
to
conduct. The collector of
Q2636 is
connected
to
the emitter of
Q2624,
forward
biasing
Q2624. The collector of
Q2624
pulls the emitter
of
Q2620 negative enough
to
forward bias Q2620. Tran-
sistor
Q2620 supplies current through
Rt
to
hold
both
inputs of the B Miller
op
amp at the same voltage. Also, a
HI from the B trigger amplifier
(Q2602
and
Q2604)
holds
off
Q2622.
2
After
A
Sweep
Starts.
When
the A
Sweep
Generator
is
triggered,
the
negative-going
A
sweep
ramp
be-
gins to
appear at
pin 2
of U2790
which is
connected
to
the
base of
Q2636.
As
the
base
of Q2636
goes
less
positive,
Q2636
turns
on
harder
causing
its
collector
to go
less
negative.
The
collector
of Q2636
is
connected
to
the
emit-
ter of
Q2624. As
the
collector
of Q2636
goes
less
negative,
the forward
bias
on
Q2624 is
decreased,
which
decreases
its
collector
current.
Since
Q2624
supplies
the
current
through Q2620,
the
current
through
Q2620
also
decreases.
This
causes
the
inverting
input
of
the
B
Miller op
amp
to
try
to go
more
positive.
To
compensate,
the
output
of the
B
Miller op
amp
supplies
current
through
Ct
and
Rt
to
hold
both inputs at
the
same
voltage.
Ct
charges at a
rate
deter-
mined
by
the A sweep
ramp.
The
resulting
ramp at
pin 2
of
U2690
has
the same
slope as
the A
sweep
ramp
and
is
internally
connected
to
pin
5
of U2690.
This
signal is
con-
nected to the
Horizotal
Preamplifier and
provides
hori-
zontal
deflection
for both
the A
and
B
portions
of
the
display.
3 When
B Sweep Gate is
Generated.
When a
B sweep gate is
generated
by
the
B
Trigger
Generator,
the
base of Q2622 steps
negative,
turning on
Q2622
which
turns
off 02620. B
sweep
generation continues as in the
A
INTEN
or B
DLY'D
modes. See
4-3.
b.
(5)
(a) 3
through 7.
(6)
Horizontal
Preamplifier.
(a)
The Horizontal
Preampifier is contained
within
a single
integrated circuit (U2900).
The Horizontal Preamp-
lifier amplifies the sweep
ramp
outputs
from the
A
and
B
Sweep Generators
and supplies the amplified signal
to the
Horizontal
Amplifier in the Main Module. In the
X-Y
mode,
the
CH
1
Preamplifier output is supplied to the Horizontal
Peramplifier
to
provide
horizontal
(X axis)
deflection.
(b)
The following
lists the pin numbers
of U2900
and
their functions.
1 Pin
1,
Magnifier
Registration.
Used in con-
junction with pin
8 to adjust magnifier registration.
Adjust-
ment is correct when display does
not shift horizontally
when switching
between normal and
magnified
displays.
2
Pin
2,
Sweep. Output
for
the
negative-going
signal which is supplied to the
Horizontal
Amplifier in the
Main Module.
3
Pin
3,
Gain. Used
in conjunction
with pin
6.
The
resistance between pins
3 and
6 determines
the ampli-
tude
of the signal
at pins 2 and
7. Decreasing
this resistance
increases
gain. The
XI 0 Magnifier
switch, when
pushed,
de-
creases
this resistance
by
a
factor of
ten and
therefore in-
creases
the gain
by
a
factor
of ten.
4
Pin
4,
—5
Volts. Connection for the
—5
volt
supply.
^
Pin
5,
Current Source.
Sets current levels
within
U2900.
6
Pin
6,
Gain. See pin 3.
7
Pin
7,
+Sweep.
Output
for
positive-going
signal which is
supplied to
the
Horizontal
Amplifier in the
Main Module.
8
Pin
8,
Magnifier Registration. See pin
1
.
9 Pin
9,
B Sweep
Input. The output
of the
B
Sweep
Generator is connected
here. The more
positive
of the
levels connected to
pins
9
and
10
is
internally con-
nected to
the amplifier and
provides the output at
pins
2
and 7. The
more
negative level on pins 9 and 10 is
ignored.
10
Pin
10,
A Sweep
Input. The output of the A
Sweep
Generator
is
connected here. See
pin
9.
4-19
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