Channel Yb Vertical Amplifier; Triggering; Trigger Unit - Philips pm3232 Instruction Manual

68
3.1.
1.8.
Output
amplifier
From
the
wiper
of
AMPL.
potentiometer R4, the
signal
is
applied to the base.of transistor
TS66
which
is
part
of
a
differential amplifier.
By
varying the
series
feedback
of
this
amplifier
by means
of potentiometer
R1
1
1,
the
overall
gain of the
Y/\ channel can be
set.
The RC
combination R113-C62
corrects the gain factor
at high
frequencies.
The
Y
shift
voltage derived
from
POSITION
potentiometer R1
1
is
applied to the base of
transistor
TS67.
If
BEAM SELECTOR
switch
SK14
is
not depressed, the voltage
on
the base of
TS67
is
such that the
trace
is
shifted off the screen
and cannot
be
brought back with
the
POSITION
potentiometer.
From
the differential amplifier the
signal
is
fed to the
final stage
which
consists off
two
single-ended push-pull
sections,
viz.
TS57,
58, 59,
68 and TS69,
73, 74, 76.
From
these
two
sections,
the
signal
is
applied to the
Y
deflection
plates.
The
circuit
with
transistor
TS56
wilt
be discussed together with the
c.r.t.
circuitry (section
3. 1.6. 3.).
In
position
X
via Y/\,
the signal
is
fed to the
X
output
amplifier
via
emitter follower
TS75.
In this
case the
channel
Y^
output amplifier
is
inoperative.
3.1.2.
CHANNEL Yb
VERTICAL
AMPLIFIER
As
this
channel
is
identical to
channel
Y
/\
with exception
of the circuitry for external
X
deflection, the
description of channel Y;\
also
holds
good
for
channel
Yg. Components
are assigned
in
the
200-299
range
(corresponding
to
numbers
in
the 1-99 range for channel
Y^)
and
in
the
300-399
range
(corresponding
to
range
100-199
in
channel
Y/\).
3.1.3.
TRIGGERING
The
trigger unit comprises the following
circuits:
a
trigger pre-amplifier,
a
differential amplifier, a
sync separator and
a
trigger-pulse shaper.
The
circuit
diagram shows
all
triggering
push-buttons
in
their released positions.
PICK-OFF STAGE
^
ya
channel
Fig. 3.3.
Trigger unit
3.1
.3.1. Trigger pre-amplifier for internal triggering
If
Y/\ push-button
SK4
is
depressed,
trigger pick-off stage
TS64
in
the
Y/\ channel and
transistor
TS402 form
together an
amplifier
with
series
and shunt feedback. Y/\ push-button
SK4
is
only
a
mechanical
release
for
Yb
push-button
SK5
and
is,
therefore,
not included
in
the circuit
diagram;
thus,
SK4
depressed corresponds
to
SK5
released.
The
gain of trigger pre-amplifier
is
determined by
the
ratio
of the
shunt feedback
resistance
R412 and
the series-feedback resistance
in
the emitter
circuit
of
transistor
TS64.
If
Yb
push-button
SK5
Is
depressed, trigger pick-off stage
TS264
In
the
Yg
channel and
transistor
TS402 form
the trigger pre-amplifier.
3.1. 3.2. Trigger pre-amplifier for external triggering
If
EXT.
push-button
SK6
is
depressed,
transistors
TS402
and TS401 form
together
a similar
amplifier
with
series-
and shunt- feedback
as
described
in
section
3.
1.3.1. Transistor
400
serves
as
an inverter for the triggering
signal,
so that the next stage
is
driven
in
the correct phase.