Sharp LC-60LE660U Service Manual page 51

Is the audio output from the monitor set at "Variable" or "Fixed" on the menu screen?
Check IC3301(CPU) and its peripheral circuits.
YES
Are there the audio signal outputs at pins (19)(AV_OUT_L) and (20)(AV_OUT_R) of IC3301 (CPU)?
Check the line between IC3301 and J502 and their peripheral circuits.
YES
Check the Cable and connected equipment condition.
Does the signal come to 1pin of LAN-jack J509?
(see fig-1, fig-2)
YES
Does the signal come to 28 pin of IC3301?
(see fig-2)
YES
Check IC3301 and its peripheral circuits.
No monitor audio output
No connect network
NO Check the interface device and peripheral circuits.
NO Check the line between J509 and IC3301.
Check the LAN-jack J509
J509
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LC-60/70LE660U,C6600U
NO
NO