Table of Contents
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1. POWER SUPPLY
The power supply circuit of the AAl -A chassis
comprises
a primary
rectifier
smoothing
circuit,
an oscillation
circuit,
a control
circuit
and an
output rectifier circuit.
The AC input voltage is rectified at the double or
full-wave
rectifier
smoothing
circuit,
and an
unstable
DC voltage
is generated
at both
terminals
of the smoothing
capacitor
C307. The
double
or full-wave
rectifier
circuit
is build by
switching
the
triac
on
or
off
in
IC501
<STR81145A>.
This voltage
is supplied
to the
oscillation
circuit,
which
is composed
of a
blocking
oscillator
circuit
that switches
the
switching transistor Q313 ON and OFF.
A square-wave
oscillation
is generated
in the
input
winding
according
to operation
of the
control
circuit.
A square-wave
with amplitude
dependent
on the turns ratio of the input and
output windings is obtained in the output winding.
This is rectified in the output rectifier circuit, and
the desired DC voltage is produced.
2. IF& DEFLECTION
(TDA8361/8362)
The
IF output
signal
from
the tuner
passes
through the SAW filter, and it is inputted into pins
45 and 46 of IC101.
Within the IC, the IF signal passes through the IF
amplifier,
video
detection
and video
amplifier
circuits,
and
is outputted
from
pin 7 as a
composite video signal.
In the monaural
model,
this composite
video
signal
passes
through
the
5.5 MHz(B/G)/
6. 0MHz(l)/6.5MHz(
D/K)/
4.5 MHz(M)
sound
bandpass
filtering
circuit, and it is inputted
into
pin5 of IC101. In the stereo model, the SIF signal
is supplied from pin 14 of IC181 <TDA2546A>
to
pin 5 of IC101
through
the sound
bandpass
circuit for modulation
of the main carrier. In the
IC101, this sound
IF signal passes through
the
SIF amplifier, FM detector, external audio switch
and audio output circuit, and it is then outputted
from pin 50 as audio
drive
signal
(Monaural
model).
In the stereo
model,
the main audio
signal is fed from pinl to the stereo controller
IC
(MC44131PB).
The video signals
applied to pins 13 or 15 are
separated
into vertical-
and horizontal-sync.
signals respectively
by the sync. separator
in the
Ic.
The horizontal
oscillator
requires
no external
components
and
is fully
integrated.
This
oscillator is always running when the start-pin 36
–
is supplied
with 8V, and the horizontal
drive
signal is outputted
from pin 37. VR401 is used
for horizontal centring adjustment.
The separated
vertical
sync.
signal
from the
sync.
separation
circuit
passes
through
the
vertical-separation
circuit,
and is applied
to
trigger divider circuit.
The horizontal oscillation pulse and vertical sync.
pulse are monitored
by the trigger divider circuit
to select either the 50Hz or 60Hz system,
and
automatically
adjust the vertical amplitude.
The output signal from the trigger divider triggers
the vertical
oscillator
circuit
whose
external
timing components
consist of R402, C401 to pin
42, and the vertical ramp signal is outputted from
pin 43. VR451 is for controlling the amount of AC
feedback
applied to pin 41 for adjustment
of the
_
vertical amplitude.
3. VIDEO CHROMA
(TDA8361/8362)
The composite
video signal output from the pin 7
of IC101, passes through
Q122, and the sound
traps
X124,
X125,
X126,
X127
to reject
the
sound carrier components,
is then supplied to pin
13 through
the equalizing
circuit
consisting
of
Q1 35, Q132 and Q134. The external video signal
from SCART or other AV terminals
is supplied to
pin 15.
The video
signal
input to pin 13 or pin 15 is
separated
into luminance
(Y) signal and chroma
signal in IC1 01. These pins are also common to
the H/V-sync.
separation
circuit
input already
described.
The peaking
of Y signal
is adjusted
by DC
_
voltage on pin 14.( ''SHARPNESS"
control)
The chroma signal is divided
into R-Y and B-Y
chroma
signals,
which
are demodulated
and
output from pin 30 (R-Y) and pin 31 (B-Y). These
chroma
signals pass through
the 1H delay line
circuit (IC270), and are re-inputted
at pin 29 (R-
Y) and pin 28 (B-Y). These R-Y/B-Y signals pass
through
the RGB matrix
circuit
and the RGB
selector
circuit
of IC101.
The internal
RGB
signals are generated
in the RGB matrix circuit
and the RGB selector,
consisting
of linear
amplifiers,
clamps and selects either the internal
RGB signals
or the external
RGB signals
input
from pin 22 (R) , pin 23 (G), pin 24 (B). Selection
is controlled
by the voltage
at the RGB switch
control
(pin 21) and mixed
RGB modes
are
possible since the RGB switching is fast.
—
-4-
AA1-A
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