Sharp C6400U Service Manual page 137

Is the audio output from the monitor set at "VARIABLE" or "FIXED" on the menu screen?
YES
Are there the audio signal outputs at pins (AJ31) (HP_MON_L) and (AJ32) (HP_MON_R) of IC3303 (CPU)?
YES
Does the audio signal come from pins (2) (MONI_HP_L) and (11) (MONI_HP_R) of IC2704 (Line-out Amplifier) to pins (3) (L) and (2) (R) of J504?
YES
Check the connector (J504) and their peripheral circuits, and speakers and the Cable.
Does the signal come to 1pin of LAN-jack J9501?
(see fig-1, fig-2)
Does the signal come to AD32 pin of IC3303?
(see fig-2)
Check IC3303 and its peripheral circuits.
fig-1
LC-52/60/70LE640U/C6400U,LC-80LE633U/844U (1st Edition)
No monitor audio output
Check IC3303 (CPU) and its peripheral circuits.
Check IC3303 (CPU) and its peripheral circuits.
Check the line between IC2704 and J504 and their peripheral circuits.
Check the AUDIO_MUTE and HP_MUTE lines and its peripheral circuits (Q506,
Q510, D2711, etc.).
No connect network
NO
NO
LAN-jack J9501
1pin
NO
NO
NO
YES Check the interface device and peripheral circuits.
(power-LED of hub, LINK-LED of hub)
YES Check the line between J9501 and IC3303.
Check the LAN-jack J9501.
fig-2
6 – 19