Tektronix 465M User Manual

AIR FORCE
T033A1-13-496-1
NAVELEX
0969-LP-170-0010
Operation
Instructions
^
Retrace. At the
beginning of holdoff,
the
out-
put
of the Miller
op amp and pin
2 of U2790 are
at about
—2.4
volts.
This voltage is supplied
to the input
of
a
non-
inverting amplifier within
U2790.
This amplifier
tries
to
pull pin 4 of
U2780, and the inverting
input
of the Miller
op
amp,
less positive.
To compensate,
the output of
the
Miller
op amp rapidly goes positive
discharging
Ct.
The re-
sulting
positive-going ramp
provides
retrace.
(5)
B
Sweep Generator.
The
B Sweep Generator
con-
sists of
U2690
and
associated
circuitry.
The B Sweep
Gen-
erator integrated
circuit
(U2690)
is the same
as the
A
Sweep Generator
integrated
circuit
(U2790). Both
are dis-
cussed
in paragraph
4-3.
b.
(4)
(a). Figure
4-8
shows
a
simplified
diagram of
the
B Sweep
Generator.
Figure
4-9
shows
the waveforms
produced
during
B
sweep generation.
Figure
FO-6 shows
a complete
schematic
diagram
of
the B
Sweep
Generator.
(a)
Sequence of
Events During
B Sweep
Gen-
eration
in B DLY'D
or A INTEN
Mode. Refer
to
Figure
4-8
and Figure
4-9
during the
following
discussion.
Figure
FO-6
shows
a complete
schematic
diagram
of the
B Sweep
Generator.
J.
Before
B
Delayed
Gate
Generation.
In the
B
DLY'D
or A
INTEN
modes,
the
base
of
Q6236
is
set
to
about +2
volts
through
the
HORIZ
DISPLAY
switch
(S2650).
The
following
conditions
exist
before
the
gen-
eration
of
a B delayed
gate
at pin
16 of
U2790.
The
B
trigger
amplifier
(Q2602
and
02604)
supplies
a
HI
to the
base
of
Q2622
which
biases
off
Q2622.
The
B sweep
start
voltage
(about
+2
volts
from
pin
2 of
U2690)
is
applied
to
the
base of
Q2632.
Bias
resistors
set
the
base of
Q2636
to
about +2
volts
also.
Ideally
Q2632
and
Q2636
Will
conduct
equally.
The
emitter
of
Q2624
is
connected
to the
collector
of
Q2636
which
forward
biases
Q2624.
The
collector
of
Q2624
pulls
the
emitter
of
Q2620
negative
enough
(through
CR2621)
to turn
on
Q2620.
Transistor
Q2620
supplies
current
through
to hold
the
inverting
input
of
the
B
Miller
op amp
at the
same
voltage
as its
non-inverting
input
(set
by R2682).
2 At
B
Delayed
Gate
Generation.
When
the
A
Sweep
Generator
generates
a B delayed
gate
(at pin
16
of
U2790),
the
resulting
negative
step
on the
base
of
Q2672,
causes
the
B holdoff
comparator
(Q2672 and
Q2674)
to
switch
states and
remove
B holdoff
from
the
B Trigger
generator.
3 At B
Sweep Gate
Generation.
When a B
sweep gate is generated
by the B Trigger
Generator, the
B
trigger
amplifier
(Q2602 and
Q2604)
switches,
which pulls
the base of Q2622
negative.
Transistor
Q2622 turns on,
pulling the emitter of
Q2620 less
negative.
This turns
off
Q2620. This begins
generation of
a
B ramp.
When the
B
ramp
(at
pin
2
of
U2690) begins going
less positive,
it turns
off
Q2636. The
emitter of Q2624 is now
connected
to
—5
volts through R2638.
Transistor
Q2624 remains on,
sup-
plying
the collector current for
Q2622.
4 During B Ramp
Generation.
When Q2620
turns off,
Ct
begins charging
through
Rt.
As
Ct
charges, the
inverting
input of
the
B
Miller
op
amp
tries
to
go
more
positive.
To compensate,
the
output
of the
B
Miller
op
amp
supplies current
through
Ct
and
Rt
to hold the in-
verting input
at
the
same voltage
as the non-inverting
input
(set
by
R2682).
Since
the resulting
voltage
across
Rt
is
constant,
the current
through
Rt
and
Ct
is constant.
Charging
Ct
with
this constant
current
produces
a linear
negative-going
ramp
at
pin
2 of
U2690.
The slope
of
the
ramp
is determined
by the values
of
Rt
and
Ct
which
are
selected
by the
B TIME/DIV
switch
(S3200).
The
ramp
at
pin
2 of
U2690 is
internally
connected
to pin
5 whenever
pin
7 is
LO.
Pin
7 is
LO in the
B DLY'D
mode
and
HI in
the
A INTEN
mode.
The
B Sweep
Generator
does
not
pro-
vide
horizontal
deflection
in the
A INTEN
mode,
it only
supplies
additional
unblanking
current
to intensify
the
display
during
the
time
a B sweep
ramp
is being
generated.
5 Sweep
Stop. When the
ramp
at
pin
2 of
U2690
reaches about
—2.4
volts, the
emitter
of Q2629
be-
comes sufficiently
negative
to
forward
bias
Q2629. When
Q2629
turns on
its collector
becomes
sufficiently
negative
to turn
on
Q2620. The resulting
current
through
Q2620
flows
through
R^ and holds
the inverting
input
of
the B
Miller
op amp
at
the
same voltage
as the non-inverting
input.
The
B Miller
op amp no
longer
supplies
current
to
Ct
and the
voltage on pin
2 of
U2690
remains
at about
—2.4
volts.
The B Sweep
Generator
does not
reset
at
this
time. If
it
did reset,
it might
be possible
to trigger and
generate
another
B sweep ramp
before
A sweep
ends.
This
would
produce
an
erroneous
display.
The
gate at
pin 10
of
U2690 does not
initiate
B
holdoff,
it
only
supplies
a
signal
to the
-t-B
GATE
OUT
Amplifier
in the Main
Module.
6 Retrace.
At the end
of
a
sweep,
the holdoff
gate from
the Sweep Control
circuit resets
both the
A and
B Trigger Generators.
When the B Trigger
Generator resets,
the
B trigger amplifier
(Q2602 and
Q2604) switches and
pulls
the base of Q2622 HI. This
turns
off
Q2622. When
Q2622 turns off,
it allows the
collector of Q2629
to
pull
the
emitter of Q2620
more negative
which increases
the
forward
bias on
Q2620. The increased forward
bias
on
Q2620
tries to increase the
current through R^
and force
the inverting
input of the B Miller
op amp less
positive.
To
compensate, the
output of the
B
Miller
op
amp
rapidly
goes
positive, discharging
C^. The resulting
positive-going
ramp on pin
2 of U2690 provides
retrace.
4-16

Tektronix 465M Specifications

General

Brand	Tektronix
Model	465M
Category	Test Equipment
Language	English