Sharp LC-42SD1E (serv.man4) Service Manual ▷ View online
LC-42SD1E/RU
4 – 1
LC-42SD1E
Service Manual
CHAPTER 4.
TROUBLESHOOTING TABLE
[1] TROBLESHOOTING TABLE
Turn on AC source.
Check AC input and output connector. Are they ok?
No
Insert connectors correctly or change them.
Turn on again.
Turn on again.
Yes
Check F7001, R7805, R7901. Are they ok?
No
Change F7001, R7805, R7901. Turn on again.
Does fuse open again?
Does fuse open again?
Yes
No
Yes
Check voltage of C7912. Does it equal 15V?
Yes
No
Check IC7901, R7920, R7921.
Check BD7001, D7803, Q7801, Q7612, Q7602,
Q7901, IC7801, IC7604, IC7901.
Q7901, IC7801, IC7604, IC7901.
Is BU5V (PA pin21+ and pin22-) output 5V?
Is UR5V (PA pin15+ and pin16-) output 5V?
Is UR37V (PA pin1+ and pin2-) output 35V?
Is UR5V (PA pin15+ and pin16-) output 5V?
Is UR37V (PA pin1+ and pin2-) output 35V?
No
Check IC7901, Q7901, D7951, L7951, C7270, C7272, D7271,
D7272, Q7270.
D7272, Q7270.
Yes
Is P-con1 (PB pin1 and pin3) signal correct?
No
Check PB (pin1 and pin3), Q7240, Q7241.
Yes
Is UR13V (PA pin6+ and pin7-) output 13V?
Is S24V (PC pin3+ and pin5-) output 25.5V?
Is S24V (PC pin3+ and pin5-) output 25.5V?
No
Check D7180, IC7150, D7150, L7150, D7240, IC7241, L7241.
Yes
Is P-con2 (PB pin2 and pin3) signal correct?
No
Check PB (pin2 and pin3), Q7309, IC7304.
Yes
Is voltage of C7800 400V?
No
Check IC7801, L7802, Q7801, D7803.
Yes
Is INV24V (LD pin5+ and pin6-) output 24V?
No
Check R7805, IC7604, Q7602, Q7612, D7200, D7201, L7200.
LC-42SD1E/RU
4 – 2
No sound (1) (during the reception of TV broadcasting)
No audio output during UHF/VHF reception
Checklist;
1) Is the volume set to MIN or MUTE on the remote control?
••• Set the desired volume.
2) Are headphones connected to HEADPHONE (J1301)?
••• Disconnect them.
3) Is ANT-CABLE disconnected or connected improperly?
••• Connect it correctly as per the operation manual.
Is the audio signal (L/R)
sent from pins (28) and
(27) of IC3002 (VCT)?
NO
Is the SIF signal (SIF_IN+)
sent to pin (31) of IC3002
(VCT)?
sent to pin (31) of IC3002
(VCT)?
YES
Check whether +5V and
+8V are supplied to pins
(33) and (18) of IC3002
respectively. Or, check
peripheral circuits.
+8V are supplied to pins
(33) and (18) of IC3002
respectively. Or, check
peripheral circuits.
(AV-UNIT)
YES
NO
Is the audio signal of pins
(3) and (5) of IC303
(OP-AMP) sent properly?
(3) and (5) of IC303
(OP-AMP) sent properly?
NO
Check SC2704 and P1201
or peripheral circuits.
Is the S-MUTE signal “L”?
or peripheral circuits.
Is the S-MUTE signal “L”?
Is the audio signal (SIF)
sent from pin (1) of
CONNECTOR (SC2705)?
sent from pin (1) of
CONNECTOR (SC2705)?
YES
Check pin (31) of IC3002
(VCT) and peripheral
circuits.
(VCT) and peripheral
circuits.
YES
(TUNER) NO
Is the audio signal of pin
(4) of IC301/IC302
(AUDIO-AMP) sent
properly?
(4) of IC301/IC302
(AUDIO-AMP) sent
properly?
NO
Check HEAD-PHONE
(J1301) or peripheral
circuits.
(J1301) or peripheral
circuits.
Is the audio signal (SIF)
sent from pin (12) of IC201
(IF-DEMOD)?
sent from pin (12) of IC201
(IF-DEMOD)?
YES
Check connector (P201/
SC2705) and peripheral
circuits.
SC2705) and peripheral
circuits.
YES
NO
Is the audio signal output
of pins (2) and (4) of P301
(AUDIO-CONNECTOR)
normal?
of pins (2) and (4) of P301
(AUDIO-CONNECTOR)
normal?
NO
Check P301 (AUDIO-
CONNECTOR) and
peripheral circuits.
CONNECTOR) and
peripheral circuits.
Is the SIF signal sent to
pins (23) and (24) of IC201
(IF-DEMOD)?
pins (23) and (24) of IC201
(IF-DEMOD)?
YES
Check IC201 and
peripheral circuits.
peripheral circuits.
YES
NO
Check Speaker (right and
left) and wire harness.
left) and wire harness.
Is the IF signal sent from
pin (8) of TUNER
(TU201)?
pin (8) of TUNER
(TU201)?
YES
Check FL202 and
peripheral circuits.
peripheral circuits.
NO
Check whether 5V (CONT)
and 5V are supplied to
pins (1) and (7) of TUNER
(TU201) respectively.
Check SDA/SCL and AGC
signal.
and 5V are supplied to
pins (1) and (7) of TUNER
(TU201) respectively.
Check SDA/SCL and AGC
signal.
YES
Replace TUNER (TU201).
LC-42SD1E/RU
4 – 3
No sound from external input devices (2)
No sound from an external input device connected to EXT1
(SCART1).
<EXT1>
Is IN1-L audio signal sent from pin (6) of SCART1 terminal
(J1101) to pin (14) of IC3002 (VCT)?
Is IN1-R audio signal sent from pin (2) of SCART1 terminal
(J1101) to pin (13) of IC3002 (VCT)?
NO
Check pins (6) and (2) of SCART1 and connection to an external
input device.
input device.
YES
Is the audio signal properly sent from pins (28) and (27) of
IC3002?
IC3002?
NO
Check IC3002 or peripheral circuits.
YES
Is the audio signal of pins (1) and (7) of IC303 (OP-AMP) sent
properly?
properly?
NO
Check IC303 or peripheral circuits.
YES
Is the audio output signal of pins (13) and (16) of IC302/IC301
(MAIN-AMP) normal?
(MAIN-AMP) normal?
NO
Check IC302/IC301 (MAIN-AMP), HEADPHONE and peripheral
circuits.
circuits.
YES
Check CONNECTOR (P301) and Speaker (right and left).
No sound from external input devices (2)
No sound from an external input device connected to EXT2
(SCART2).
<EXT2>
Is IN2-L audio signal sent from pin (27) of SCART2 terminal
(J1101) to pin (12) of IC3002 (VCT)?
Is IN2-R audio signal sent from pin (23) of SCART2 terminal
(J1101) to pin (11) of IC3002 (VCT)?
NO
Check pins (27) and (23) of SCART2 and connection to an
external input device.
external input device.
YES
Is the audio signal properly sent from pins (28) and (27) of
IC3002?
IC3002?
NO
Check IC3002 or peripheral circuits.
YES
Is the audio signal of pins (1) and (7) of IC303 (OP-AMP) sent
properly?
properly?
NO
Check IC303 or peripheral circuits.
YES
Is the audio output signal of pins (13) and (16) of IC302/IC301
(MAIN-AMP) normal?
(MAIN-AMP) normal?
NO
Check IC302/IC301 (MAIN-AMP), HEADPHONE and peripheral
circuits.
circuits.
YES
Check CONNECTOR (P301) and Speaker (right and left).
LC-42SD1E/RU
4 – 4
No sound from external input devices (2)
No sound from an external input device connected to EXT3.
<EXT3>
Is IN3-L audio signal sent from pin (3) of J1201 terminal to pin
(16) of IC3002?
Is IN3-R audio signal sent from pin (5) of J1201 terminal to pin
(15) of IC3002?
NO
Check pins (3) (J1201) and (5) (J1201) of EXT3 and connection
to an external input device.
to an external input device.
YES
Is the audio signal properly sent from pins (28) and (27) of
IC3002?
IC3002?
NO
Check IC3002 or peripheral circuits.
YES
Is the audio signal of pins (1) and (7) of IC303 (OP-AMP) sent
properly?
properly?
NO
Check IC303 or peripheral circuits.
YES
Is the audio output signal of pins (13) and (16) of IC302/IC301
(MAIN-AMP) normal?
(MAIN-AMP) normal?
NO
Check IC302/IC301 (MAIN-AMP), HEADPHONE and peripheral
circuits.
circuits.
YES
Check CONNECTOR (P301) and Speaker (right and left).
No sound from external input devices (2)
No sound from EXT4 (AUDIO) connecting an external input
device.
<EXT4>
Is D-SUB-L audio signal sent from J2702 to pin (15) of IC2704?
Is D-SUB-R audio signal sent from J2702 to pin (2) of IC2704?
YES
Is D-SUB-L audio signal sent to pin (10) of IC3002?
Is D-SUB-R audio signal sent to pin (9) of IC3002?
Is D-SUB-R audio signal sent to pin (9) of IC3002?
YES
Is the audio signal properly sent from pins (28) and (27) of
IC3002?
IC3002?
NO
Check IC3002 or peripheral circuits.
YES
Is the audio signal of pins (1) and (7) of IC303 (OP-AMP) sent
properly?
properly?
NO
Check IC303 or peripheral circuits.
YES
Is the audio output signal of pins (13) and (16) of IC302/IC301
(MAIN-AMP) normal?
(MAIN-AMP) normal?
NO
Check IC302/IC301 (MAIN-AMP), HEADPHONE and peripheral
circuits.
circuits.
YES
Check CONNECTOR (P301) and Speaker (right and left).