Sharp LC-42SB45U - Power Unit Operation Check; The Sound Is Not Emitted from Speaker Though the Picture Has Come out; Troubleshooting Table; Chapter 4. Troubleshooting Table

2008-03-14
LC-42SB45U
33
CHAPTER 4. TROUBLESHOOTING TABLE
[1] TROUBLESHOOTING TABLE
Power unit operation check.
↓
LINE_FILTER_UNIT: ↓ YES
POWER_UNIT
↓YES
↓YES
↓YES
↓YES
The sound is not emitted from the speaker though the picture has come out.
↓
No sound output in all modes?
TEREMINAL UNIT: ↓
↓YES
↓YES
↓YES
Are the power cord and harness in the unit properly connected?
NO
Connect the power cord and harness properly, and turn on the
p
ower.
Is F901 normal?
NO
LINE_FILTER_UNIT:
Isn't L901,L902,RV902,C908,C909,C901,C902, etc. out of
order? Moreover, whether the short-circuit with the
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.
Is BD901 (+320V) output? (Set the main power SW to OFF.)
* When power on/off switch is on ‧‧‧ About +400V
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
Is a voltage of +5V applied to pin (11,12) of connector (CN902)?
(Set the main power SW to OFF.)
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.
NO
Are +24V output as for the power on/off switch when it is on?
NO
Does the inverter circuit operate normally?
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.
Similarly, is +12V output as for the power on/off switch when it is
on?
NO
Check +12V circuit of D928, L909, etc.
Is the audio signal output of pin (E26) (AL2) and pin (F25) (AR2) of
IC U400 normal?
NO
Check IC U400 and its peripheral circuits.
Is audio signal input to pin (2)(L), pin (14)(R) of IC U600 (AMP)?
NO
Check the line between IC U400 and IC U600.
Is MUTE circuit [AMP_MUTE_LINE, POWERUP_LINE] normal?
NO
Check the AMP_MUTE_LINE and POWERUP_LINE. (Q600,
etc.)