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Circuit Description
1. POWER SUPPLY
The
power supply circuit of the AAl - A chassis is
composed of a rectifier smoothing circuit, an oscillation
circuit, a control circuit and an output rectifier circuit.
The AC input voltage is full-wave
rectified by the rectifier
smoothing
circuit,
and
an
unstable
DC
voltage
is
generated
at both terminals of the smoothing capacitor
C307. This voltage is input to the oscillation circuit. The
oscillation circuit is provided with a blocking oscillator
circuit that switches the switching transistor Q313 ON and
OFF,
and an oscillation frequency
and a duty square
wave pulse are generated in the input windings according
to operation of the control circuit. A square- wave pulse
whose size is dependent on the turn 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 obtained.
2. IF& DEFLECTION
The IF output signal from the tuner passes through the
SAW filter, and it is input to pin45 and pin46 of ICI 01.
The signal input to the IC passes through the IF amplifier,
video detection and video amplifier circuits and is output
from pin7 as a composite video signal.
And after this signal is converted to impedance at Q1 34,
supplies to the video and chroma amplifier stages.
The
output
signal
from
pin7
passes
through
the
5.5MHz(B/G)/6.0MHz(
l)/6.5MHz(D/K)/4
.5 MHz(M)
filtering
circuit, and it is input to pin5 of IC1 01. The signal input to
the IC passes through the SIF amplifier, FM detector,
external audio switch and audio output circuit, and it is
then output from pin50 as audio drive signal.
The sync. - separation circuit separates the video signals
applied to pinl 3 or pinl 5 to vertical- and horizontal- sync.
signals respectively.
The horizontal oscillator requires no external components
and is fully integrated. The oscillator is always running
when the start- pin36 is supplied with 8V.
Horizontal drive signal is output from pin37. VR401 is for
adjustment of the horizontal centering.
The separated vertical sync. signal from sync. separation
circuit passes through the vertical - separation circuit, and
applied to trigger divider circuit.
The horizontal oscillation pulse and input vertical sync.
pulse are monitored by the trigger divider circuit, and
switching 50Hz and 60Hz system, the vertical amplitude
automatically adjusted for 50Hz and 60 Hz.
The output signal from the trigger divider is triggered
vertical oscillation circuit consisting of R401 ,C402 and
pin42, and vertical drive pulse is output from pin43.
VR451 is for changing the amount of AC feedback applied
to pin41 and for adjustment of the vertical amplitude.
3. VIDEO CHROMA
The composite video signal output from the pin7 of [Cl 01
passes through Q122/ Q1 34, and it is supplied to pin13.
The external video signal output from AV terminal passes
through IC801, and it is supplied to pin15.
The video signal input to pin13 or pin15 is separated to
luminance (Y) signal and chroma signal in IC1 01. These
pins are used in common with H/V - sync. separation
input.
The peaking of Y signal is adjusted by DC voltage of
pin14.(''SHARPNESS"
control)
The chroma signal is divided into R - Y, B - Y chroma
signals, demodulated in IC1 01,
and output from pin30 (R - Y) and pin31 (B - Y). These
chroma signals pass through the 1H delay line circuit
(IC270), and they are input to pin29 (R- Y) and pin28 ( B-
Y). These R - Y/B - Y signals pass through RGB matrix
circuit and RGB selector circuit of IC1 01. The internal
RGB signals are generated in RGB matrix circuit and the
-
RGB selector, consisting linear amplifiers, clamps and
selects either the internal RGB signals or the external
RGB signals input from pin22 (R) , pin23 (G), pin24 (B).
Selection is controlled by the voltage at the RGB switch
control (pin21 ) and mixed RGB modes are possible since
RGB switching is fast.
The RGB switch also functions as a fast blanking pin by
blanking the
RGB
output stages;
here
internal
and
external RGB signals are overruled.
The colour gain is controlled by DC voltage of pin26.
("COLOUR" control)
The contrast control voltage present at pin25, controls the
RGB signal gain, and the brightness
control voltage
present at pin17 controls DC level of RGB signals.
The
RGB
signals
are
finally
buffered
before
being
available at the RGB output pins [ pin20 (R), pin19 (G),
pin18 (B)].
d
4. AUDIO
OUTPUT
The audio signal output from pin50 of IC101 is input to
pin2 of IC1 101 and passes through the pre - amplifier
circuit and drive circuit, after which it is input to the audio
amplifier. The audio amplifier is an SEPP (Single- Ended
Push Pull) type and output to pin8 to directly drive the
speaker.
.-.'
–4–
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