Troubleshooting Table; Power Unit Operation Check; The Sound Is Not Emitted From Speaker Though The Picture Has Come Out; Chapter 4. Troubleshooting Table - Sharp LC-42SB45U Service Manual

CHAPTER 4.

TROUBLESHOOTING TABLE

[1] TROUBLESHOOTING TABLE
↓
Are the power cord and harness in the unit properly connected?
↓ YES
LINE_FILTER_UNIT:
Is F901 normal?
↓YES
POWER_UNIT
Is BD901 (+320V) output? (Set the main power SW to OFF.)
* When power on/off switch is on ‧‧‧ About +400V
Is a voltage of +5V applied to pin (11,12) of connector (CN902)?
(Set the main power SW to OFF.)
Are +24V output as for the power on/off switch when it is on?
Similarly, is +12V output as for the power on/off switch when it is
on?
No sound output in all modes?
↓
TEREMINAL UNIT:
Is the audio signal output of pin (E26) (AL2) and pin (F25) (AR2) of
IC U400 normal?
Is audio signal input to pin (2)(L), pin (14)(R) of IC U600 (AMP)?
Is MUTE circuit [AMP_MUTE_LINE, POWERUP_LINE] normal?

Power unit operation check.

↓YES
↓YES
↓YES
The sound is not emitted from the speaker though the picture has come out.
↓
↓YES
↓YES
2008-03-14
↓YES
NO
Connect the power cord and harness properly, and turn on the
power.
LINE_FILTER_UNIT:
Isn't L901,L902,RV902,C908,C909,C901,C902, etc. out of
order? Moreover,
NO
circumference circuit is checked.
POWER_UNIT:
BD901, RV904, IC902, TH901, etc. out of order?
Moreover, whether the short-circuit with the circumference circuit
is checked.
NO
Does the PFC circuit operate normally?
(L903, L964, Q925, ZD914, D930, Q902, IC902 and etc. And,
the circuit around the protection circuit etc. is checked.)
NO Does the switching circuit operate normally?
Check circuit around the primary side (T904, IC903, Q922,
Q924, ZD911, D924, D908, ZD910, etc.), the secondary side
(D927, L907, etc.), the AC_DET circuit (ZD912, ZD913, IC911,
IC913, Q918, IC909, Q915, etc.), and the protection circuit.
Does the inverter circuit operate normally?
NO
Check circuit around the primary side (T905,Q920,Q919,IC901,
Q917,Q923,D936,D937,D932,ZD915,ZD916, etc.), the
secondary side (D901, D902, L906, L908, IC910, IC914, etc.),
the STANDBY circuit (Q915, etc.), and the protection circuit.
Check +12V circuit of D928, L909, etc.
NO
NO
Check IC U400 and its peripheral circuits.
NO
Check the line between IC U400 and IC U600.
NO
Check the AMP_MUTE_LINE and POWERUP_LINE. (Q600,
etc.)
33
LC-42SB45U
whether the short-circuit with the