Input
Cathod* Follower
HORIZONTAL-DEFLECTION
SYSTEM
The
input
cathode
follower,
V330,
isolates
the
input
circuits
from
changes
in capacitance
as
the
VARIABLE
control
is
rotated.
R330
is
a
current-limiting
resistor
to
limit
grid
current
in the
event
an
excess
voltage is
applied
to
the
input.
The
opposite
cathode
follower,
V340,
balances
the
drift
in
V330
caused
by
heater-voltage
changes.
I nput
Amplifier
The
input
amplifier stage is
a
common
cathode phase-splitter amplifier.
Coils
L351
and
L361
provide
high-frequency
peaking.
The
VARIABLE
VOLTS/CM
control,
R356, varies
the
gain
by varying
the
degeneration
in
the
cathode
circuit.
Vertical
positioning
is
produced
by
two
dual
potentiometers,
R368,
connected
to the
plates
of
the
amplifier
so
that
current
through
one
plate
load
is
increased as current through
the
other
plate load is
decreased.
Since the
amplifier
is
de
coupled,
the
change
in
the
plate
voltage
which
occurs
changes
the
position
of the trace
on
the
cathode-ray
tube.
The
rc
networks,
R352,
C352
and R362,
C362,
provide
compensation
for
the
reduction
in
gain
at
very-low
frequencies
which is
a
characteristic
of
high-conductance
amplifiers.
Output
Amplifiers
Cathode
followers
V370A and
V370B
drive
the
output amplifiers
through
series
peaking
coils
L390
and
L400.
The
GAIN
ADJ.
control,
R396, sets
the
gain
of
the
amplifier
to
agree
with
the
front-panel
calibration.
Plate
current
for the
output
amplifiers
is
supplied
by
the
delay-line
termination
resistors,
R485
and
R486.
Delay Line
The
balanced delay
line delays
the
signal
until
the
sweep
starts
and
the
ert
is
unblanked.
The
trigger
signal
is
taken
from
a
coil
which
serves
as
the
first
section
of
the
delay
line.
Each
section
of
the
line
is turned
for
optimum
response
to
a
square
wave.
Trigger
Amplifier
The
TRIGGER SELECTOR
switch
with
the
black
knob,
SW20,
selects
the source
of
trigger
ing
voltage
and
arranges
the
trigger-amplifier
input
circuit
to
produce
negative-going
output
for
either
negative-going
or
positive-going
por
tions
of
the input
signal.
The trigger
amplifier,
V10,
is
a
grounded-
grid
cathode-coupled
amplifier.
A capacitor,
C4, can
be switched
into
the
grid
circuit
to
remove
the
de component
of
the
trigger
signal.
Output
is always
taken
from
the
pentode plate,
but
the TRIGGER
SELECTOR switch
connects
either
the
pentode
grid
or the
triode grid
to
the
input-signal source.
The
opposite
grid
is
connected
to
a
de
bias
source,
adjustable
by
means
of
the
TRIGGERING
LEVEL
control.
This
bias
voltage
determines
the
voltage
on
the
pentode
plate.
In
the
AC
and
DC
positions
of the
TRIGGER
SELECTOR
switch,
the
voltage
on
the
pentode
plate
is de
coupled
to
the
grid
of V30A.
Trigger
Shaper
The
trigger-shaper
stage consists
of
V30
connected
as
a
dc-coupled
multivibrator.
In
the
normal, or quiescent,
state
the
V30A
section
is
conducting
and its plate
is
down.
The
grid
of
the
V30B
section
is
de
coupled to
the V30A
plate
through
divider
R38,
R39
and
R40,
which
holds
the
"
B"
grid
below plate-current
cutoff.
As the
trigger
signal
drives
grid of
V30A
in
the
negative direction the cathodes of both
tubes follow
the
grid
down
until
V30B
starts
to
conduct. At
this
point
the
plate voltage
of
V30A
and
the
B
grid
rises
with
it.
The
V30B
cathode
rises
with
its
grid
carrying
the
"
A" cathode
with
it
and
V30A
cuts off.
The
transition
occurs very
rapidly,
regard
less
of
how
slowly
the
V30A
grid
signal
falls.
The
steep
negative-going
step
at
the
plate
of
V30B
is differentiated
by
an
rc
network
including
C109
shown
in the
sweep
diagram,
and
the
sharpened
pulse
trips
the
sweep multi
vibrator.
Trigger
Mode Switch
The
TRIGGER
SELECTOR
switch
with
the
red
knob,
SW5, has four positions
which
arrange
3-2
Circuit
Description
-
Type
515/515A
AA