XOCECO LC20H3D, Service Manual

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Target After Download. Click FLASH pushbutton, it’s ready to run. For other settings, please refer to the
Fig. Above (already defaulted by the system, normally no need to change).
4.Switch on TV set the FLASH write program begins to run;
5.After FLASH write is over, push button “cancel” will become flash. Then shut the main power supply
and it’s OK just switch it on again.
Note: Do not shut the power off or turn the TV set on during the FLASH write. Otherwise it
may lead to no way for flash to rewrite.
Brief introduction and working principle of L20H3
LC20H3 multi-media liquid crystal TV broadcast and receiving set adopts liquid crystal display
screen of LG 20.1, which is provided with NTSC color system receiving function in addition to AV
input,S-VHS input,high definition signal port for component YPrPb/YcbCr,PC VGA port, earphone output
and other signal ports. For power supply an externally connected power adaptor is provided.
The circuitry of LC20H
3
is composed of RF module board, video signal board, digital signal picture
processor and AC-DC transformer, and DC-DC circuit board.
The working process is as follows. The radio frequency signal undergoes an integrated tuner
TUNER1 before a color full video signal is generated. This video signal then enters analog board
decoder IC N303 VCT3833 Pin19 where it is processed and it’s output as analog signals R, G, B through
Pin42, PIN43, PIN44. Audio frequency signal is processed with sound in IC N401 MSP3420G and then
output through MSP3420G Pin28 , Pin27 to SRS for surround sound processing in IC N403 M62494E.
Finally it is subject to power amplification in IC N404 TDA1517 before it is output to speaker.
VGA signal/high definition signal is input to personal computer through the main board. The signal
selected by Y/Pb/Pr through 5 way 1/2 switches IC(N1 BA7657F)is subject to reselection together with
signal TVRAIN, TVGAIN, TVBAIN through 5 way 1/2 switches IC(N5 BA7657F). Finally signals R, G, B
are selected and sent to the main processing chip IC N19 PW1306.
IC N19 PW1306 is a built-in X86 CPU of the main processing IC,externally connected by 8M
Flash(N20) memory to control the whole system. The input signal of V-port and G-port is subject to
internal arithmetic processing and then output as R, G, B signals with electric level of 24 bit TTL to
sockets JP3 and JP4, where through connection wires the signals are sent to the port of LG liquid crystal
screen and for the realization of picture reproduction.