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No video picture, no sound.
Check whether all the
voltages from the power
board to the decoder
board are normal.
Check if the reset circuit consisting of
EC21, R57,R55 ,D8,R52 and Q7 is
normal (at a high level for
milliseconds, then constantly at
0V).
Check whether there is
27MHz signal output.
Check if there is 135MHz
signal output on R102.
No video picture,
no sound.
Go
Yes
several
Yes
Yes
SDRAM(R102 SDCLK) waveform
Yes
Check U9.
4-9
No
Check the loaded circuit
CVBS (R103 point) waveform
No
Change EC21,and Q7.
Crystal oscillator Y1 and
No
peripheral components
are defected or eroded.
No
Check whether
short-circuit or bad
solder on U3, U9
Reconnect the component in
short-circuit
Trouble shooting chart
27M waveform
Yes
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