XOCECO PH-50HU31, Service Manual, Page: 14 / 41

12
Working principle analysis of the unit
The RF signal received by antenna will be sent to tuner TUN1, then IF signal will be obtained
through high amplifier and mixed frequency, through pre-intermediate amplified by VZ100, then it
will be sent to acoustic surface-wave ZZ101 to do IF filter and get better IF characteristics, then it
will be sent to NZ100 (R2S1040) to do intermediate amplification, phase-locked loop VCO and
synchronous wave detection to get video signal TV-CVBS; after pre-intermediate amplification IF
will also be sent to acoustic surface-wave ZZ100 to do filter at the same time, then it will be sent to
NZ100 to do intermediate amplification and output the second sound intermediate frequency signal
(TV-SIF).
The TV-CVBS signal output from R2S1040 together with TV-SIF will be sent to main IC NS4
(MST9U88L). Video signal of AV1, AV2, S-VIDEO, YPbPr1 and YPbPr2 will also be sent to
MST9U88L; while the audio signal of them via audio switch NW200(HEF4052BT) selection to
MST9U88L (AV1 and S-VIDEO share one audio port). Video and audio signal of VGA, HDMI will be
sent to MST9U88L, too.
The main IC NS4(MST9U88L) is a high performance and fully integrated IC, which can realize
HDMI interface processing, video demodulating, video switch selection, A/D and D/A conversion,
interlace/de-interlace processing, modes conversion, OSD and low-voltage differential output, ect.
And it also has functions of audio selection, processing and MCU.
The video signal via MST9U88L processing, output 4 pairs differential signal and 1 pair clock
signal for PDP panel display. Video signal of AV1, AV2, S-VIDEO and TV via initial selection and
processing, output video signal of AV-OUT, after double video amplifying, it will be sent to AV-OUT.
Audio signal via MST9U88L processing, output two ways; one way will be sent to sound
amplifier NA6 (MP7722DF) amplifying, then sent to speaker. At the same time, it also sent to
earphone sound amplifier N350 (BH3547F), after amplifying then sent to earphone. Another way
will be sent to D/A converter NS6 (CS4344) through I2S bus, convert to analog sound signal L/R
output through AV-OUT.