XOCECO LC-27FB26, Service Manual

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14
Working principle analysis of the unit
1. NTSC signal flow:
Antenna reception NTSC signal send to the integrative tuner FQD1236, which contains HF and IF
amplifier circuit and video decoding circuit. It is controlled by main IC ZR39660 (inside CPU)
through I2C bus. The NTSC signal via frequency tuning, HF amplification, IF amplification, system
switching and decoding, output video signal TV-CVBS of 1Vpp and sound IF signal (SIF).
TV-CVBS and AV1-CVBS, AV2-CVBS input from AV terminal, via switch IC HEF4052 to output
signal, one way send to ZR39660 for VEDIO DECODER, DEINTERLACE and SCALER, then send
to LVDS level drive for LCD screen, another way is output through AV output socket as AV OUT.
The sound IF (SIF) is fed into demodulation IC CAS220, via decoding and A/D conversion, it is fed
into ZR39660 for analog control in the format of I2S. ZR39660 outputs audio data of I2S format, it is
fed into audio D/A converter IC CS4344, output analog L/R signal. The L/R signal and sound signal
of PC/YPRPB via diverter switch HEF4052BT, send to R2S15900SP (sound processing and volume
control). Select right/left sound channel, their send to digital sound amplifier TPA3001 amplify, then
send to speaker.
2. ATSC signal flow:
Antenna reception ATSC signal send to tuner FQD1236, after frequency tuning, HF amplification, IF
amplification and SAW FILTER, output IF signal to demodulation chip CAS220, via VSB or QAM
demodulation, Sound stereo decoder, fed to ZR39660 for information source decoding in the format
of standard serial TS stream.
HD video signal via decoding to A/D conversion and OSD superposition, at last send to LVDS drive
level for PDP panel.
HD audio signal, via decoder built-in ZR39660, resumed to multi- channel sound of Dolby AC-3, at
the same time output data stream of I2S format and S/PDIF data stream. Audio data of I2S format is
fed to audio D/A conversion chip CS4344 to output analog L/R signal. S/PDIF data stream directly
output from optical fiber interface.
3. PC/YPrPb signal flow
PC and two YPBPR signal via matched resistance, it a-c couple to video switch SN74CBT3257CDR,
via switching to selected signal to Triple Video A/D Converter MST9883 A/D conversion. Send
B/G/B of 24 bit to main IC ZR39660 digital decode, image scale and OSD superposition, then send
to LVDS level drive for LCD screen.
Sound signal (PC, YPrPb) via switch diverter HEF4052BT to output signal, it send to R2S15900SP
(sound processing and volume control) switch of audio. Select right/left sound channel, their send to
digital sound amplifier TPA3001 amplify, then send to speaker.
4. HDMI signal flow
HDMI video signal is directly fed to main IC ZR39660 (with HDCP function of HDMI) digital decode,
image scale and OSD superposition, then output LVDS drive level for screen.
HDMI audio signal, via decoder built-in ZR39660,output data stream of I2S format and S/PDIF data
stream at the same time. Audio data of I2S format is fed to audio D/A conversion chip CS4344 to
output analog L/R signal. S/PDIF data stream directly output from optical fiber interface.