Sanyo 28H1, Руководство по обслуживанию

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Service Manual EH1 chassis
This chassis consists of the tuner, IF detector, audio
signal processor, video signal processor, AV selector,
double scan converter, vertical deflection, horizontal
deflection and system control circuit that controls all of
the circuit on this chassis.
The RF(radio Frequency) signal input to the tuner from
the aerial is converted to the IF(Intermediate Frequency)
signal in the tuner stage, and then, the composite video
(CVBS) signal and the SIF carrier signal are extracted at
the IF detector circuit.
The SIF carrier signal is applied to the A2 stereo
demodulator circuit and Nicam stereo demodulator circuit
respectively. The A2 stereo demodulator detects the SIF
signal (5.5MHz=Main channel, 5.74MHz=Sub channel)
input, and sends out the A2 stereo audio signals output
to the Nicam decoder circuit, and also judges that the
receiving signal is stereo or monaural, and sends out the
result to the CPU via I
2 C bus lines. The Nicam decoder
decodes the SIF signal (5.85MHz components) input and
obtains the Nicam stereo audio signals output. This IC
also sends out the status (Nicam or not) to the CPU via
the I
2
C bus lines. The obtained A2 stereo or Nicam
stereo audio signals are selected by the CPU via the I
2
C
bus and supplied to the audio processor circuit as TV
audio signal.
In the video signal processing stage, video signal output
from the IF detector circuit is supplied to the AV selector
circuit as TV video signal. The AV selector circuit selects
the output video signal from the input signal of TV video,
scart video and front video signal by the CPU via I
2
C
bus. The selected video signal is sent to the
video/chroma demodulator circuit. The video/chroma
demodulator demodulates the video signal or Y and C
signal and outputs the colour differential signal R-Y, B-Y,
Y, H-sync and V-sync signal and supplies them to the
double scan converter circuit.
The double scan converted Y, R-Y and B-Y signals are
applied to the aperture control and RGB matrix circuit.
The RGB original colour signal which are obtained at the
RGB matrix circuit drive the video output circuit. This
video output circuit also controls the automatic cut-off by
feeding back the AKB(Auto-Kine Bias) pulse on the RGB
signal during the vertical blanking period to the RGB
matrix and video control circuit.
The H-sync and V-sync signals are applied to the H/V
sync driver circuit to generate the drive signals for each
output circuit. In the vertical signal control circuit, the
vertical sawtooth signal applied to the vertical output
circuit is waveform-shaped to compensate the raster
distortion.
On the other hand, the audio processor circuit selects the
output audio signal from input signals of TV audio, front
audio and scart audio by the CPU via I
2
C bus. The
selected audio signals are sent to the 3D surround
processing circuit for adding the 3D surround effects.
These signals are again input to the audio processor IC,
and are controlled in volume, bass, treble, balance and
sound mute by the CPU via I
2
C bus. The controlled audio
signals are supplied to the audio output circuit to drive
the loudspeakers.
Main signal flow