XOCECO LC20Y19, Service Manual

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10
The unit working principle analysis
For the PAL system, when the RF signal is input to the tuner, the turner generates IF signal. Then the IF
signal goes through the pre-amplifying circuit and 38M SAW, the VIF signal and 1ST_SIF signal will be
generated. When these signals are input into the M52760E IC, the VIDEO_OUT and SIF signal will be
generated. Then these two-way signals are sent to HEF4052BT, trapper and filter, which selective output
signal according to different sound systems (PAL D/K, PAL B/G, PAL I). The audio signal returns
toM52760E IC via filter to be decoded and then is sent to R2S15900, while the video signal is transferred
to multi-system signal CVBS_TV via trapper and then is sent to FLI8125 directly.
For the NTSC system, when the RF signal is input to the NTSC tuner, the turner generates IF signal.
Then the IF signals goes through the pre-amplifying circuit and 45.75M SAW, the VIF signal and
1ST_SIF signal will be generated. When these signals are input into the M52760E IC, the VIDEO_OUT
and SIF signal will be generated. Then the SIF signal is sent to MTS decoder LA72700 to perform BTSC
stereo decoding, at last, the signal is input to R2S15900SP. The video signal is transferred to
multi-system signal CVBS_TV via trapper and then is sent to FLI8125 directly.
The AV, YPbPr/YCbCr, S-VHS and VGA signals from the input terminals, with the CVBS_TV signal, are
sent to the main IC FLI8125, after decoding, filtering, De-Interlace, Adc and Scaler, and according to
different panel, the main IC generates a 24-bit TTL signal or LVDS signal to send to the panel to recur
the picture.