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CIRCUIT DESCRIPTION
1. POWER SUPPLY
2. IF & DEFLECTION (TDA8361)
The IF output signal from the tuner passes through the
SAW filter, and it is input to pin45 and pin46 of IC201. 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 sig-
nal is converted to impedance at Q151, supplies to the
video and chroma amplifier stages.
The sync.-separation circuit separates the video signals
applied to pin13(internal video signal) or pin15(external
video
signal) 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. VR361 is for
adjustment of the horizontal centring. The separated ver-
tical-sync. signal from sync. separation circuit passes
through the vertical-separation circuit, and applied to trig-
ger 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
60Hz. The output signal from the trigger divider is trig-
gered vertical oscillation circuit consisting of C351, R356
and pin42, and vertical drive pulse is output from pin43.
VR501 is for changing the amount of AC feedback applied
to pin41 and for adjustment of the vertical amplitude.
3. VIDEO CHROMA & R.G.B. (TDA8361)
The composite video signal output from the pin7 of 1C201
passes through Q151-Q154, and it is supplied to pin13.
The external video signal output from SCART is supplied
to pin15. The video signal input to pin13 or pin15 is sepa-
rated to luminance (Y) signal and chroma signal in C201.
These pins are used in common with H/V-sync. separation
input. The peaking of Y signal is adjusted by DC voltage of
pint4. ("SHARPNESS'"
control) The chroma
signal is
divided into R-Y and B-Y chroma signals, demodulated in
4. AUDIO OUTPUT(AN5265)
The audio signal output from pin52 of 1C201 is input to
pin2 of |CO001 and passes through the pre-amplifier circuit
and drive circuit, after which it is input to the audio ampli-
fier. The audio amplifier is an SEPP (single-ended, push-
pull) OTL type and output to pin8 to directly drive the
speaker.
5. VERTICAL OUTPUT (LA7832/LA7833)
An IC (LA7832/LA7833) is used for the vertical output cir-
cuit in this chassis. The vertical drive pulse from pin43 of
IC201 is input to pin4 of IC501. This pulse drives IC501,
and vertical scanning is performed. In the first half of
scanning a deflecting current is output from pin2 and
passes through the following path:
Vcc(B4) —~ D501
—
pins —
pin2 —
DY ~
C512 -
VR501/R509. An electric charge is then stored in C512. In
the last half of scanning the current path is C512 — DY ~
pin2 — pint — VR501/R509 — C512. In this way, an
amplifying sawtooth waveform current flows directly to DY
to perform electron beam defection. Next, in the first half
of the banking period the vertical drive pulse suddenly
becomes OFF, and in order to reduce the current flowing
to DY, the current path becomes as follows by the induc-
tance of DY:
DY — pin2 — pin1 — VR501/R509 — C512 — DY. Also,
when the charge of DY has dissipated, the current path
becomes Vcc24V — pin6 — pin7 — C502 — pin3 —
pin2— DY — C512 — VR501/R509, and when the pre-
scribed current value is reached, the vertical drive pulse
becomes ON. This completes one cycle.
6. HORIZONTAL OUTPUT
A horizontal oscillation signal is output from pin37 of
IC201 and switches the drive transistor Q431. This switch-
-5-
Service manual-ECS chassis
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