Service manual

check if the EAR-INT signal is abnormal, which is in order to avoid wasting time
on checking amplifier.
Regarding the connecting with IO board, it is important that I2C signal
connects with MCU （MCU-INT、SCL－MCU、SDA－MCU）. If there is any problem with
the connecting, then the key and remote control work out.
5.3、Work Principle of I/O board
1、I/O board mainly: inputs & outputs AV signal, switches audio and video,
amplifies audio, control mini MCU and process key.
2、I/O board can be divided into three modules, a）audio module，to process,
switch and amplify audio；b）video module, to input & output video switch；c）
mini MCU module. When maintenance, if no sound, then the audio module has problem;
if no picture, then the video module has problem; if the remote control and keys
work out, then the MCU module has problem under the circumstance that IR&KEY board
is OK.
a）Audio module：is divided into small signal process and power amplification.
Small signal can be separated into: left & right audio analog signal. Analog audio
signal enters CX2069Q（UV401） via the following 7 channels: left & right audio
channels of AV2（S-VIDEO2）， left & right audio signals of SCART1 & SCART2，
left & right signals of YPbPr，left & right signals of VGA，left & right audio
signals of HDMI sent by SCALER board and the audio signal switched from digital
TUNER. The above audio signals are switched via CXA2069Q，and sent together with
SIF signal from DVB board to TDA9875（UV505） for processing. TDA9875（UV505）
mainly decoding the audio channel of SIF signal and control the volume. After
processed by the chip, 4 routes of L & R signals are output from the output end
of the chip. Among them, two routes are output from SCART1 & SCART2 after filtered
by filter web; one is output from earphone after filtered and amplified by NJM4556;
the last one is output by speaker after processed by NJW1137（UV601）and amplified
by TPA3100（UV602）.
During the whole process, UV401, UV601 and UV505 are controlled by I2C. If
the audio trouble is caused by UV401 and UV601, connect the signal via lead from
the input end of chip to output end to judge if the work is normal. If the video
trouble is caused by UV401, please judge in the same way. In the whole audio
channel, if audio output is normal, then MUTE signal is low level, otherwise,
high level.
b）Video module：four routes CVBS, one route S-VIDEO, one route RGB signal
and one route TV-CVBS signal. After switched by CXA2069Q（UV401）, one route CVBS,
one route S-VIDEO and one route RGB are input to the corresponding analog input
ports of PW106 of SCALER board respectively. In addition, the YPbPr signal of I/O
board input into the corresponding analog input port of PW106. The last route is
VGA and HDMI. HDMI is directly input to the digital port of PW106, and the input
VGA signal is sent to PI5V330Q（U1） and separated into two routes: one is input
from the analog port of PW106, while one is input from the digital port of PW106
after switched by AD9985（U6） into digital signal. In this way, PIP function can
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