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