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No video picture, no sound.
Check
voltages from the power
board to the decoder board
are normal.
Check if the reset circuit consisting
of C1, Q2, Q1,R1,R2,R3,R5,R4 is normal
(at a high level for tens of milliseconds,
then constantly at 0V).
Check whether there is
27MHz signal output.
Check if there is 128MHz
signal output on R49.
No video picture,
no sound.
Go
whether
all
the
Yes
Yes
Yes
Yes
Check U3.
No
Check the loaded circuit
No
Crystal oscillator Y1 and
No
peripheral components
are defected or eroded.
No
SDRAM(R49 SDCLK) waveform
Reconnect the component in
short-circuit
Trouble shooting chart
CVBS(L27 point) waveform
Change C1,Q1,Q2
27M waveform
Check whether
short-circuit or bad
solder on U3, U4
Yes
No
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