Read Sharp LC-20M4E (serv.man3) Service Manual online
LC-20M4E
12
TROUBLE SHOOTING TABLE
No picture, No sound
Check all the settings microprocessor's adjust process menu.
Do F701 function?
Are T701's secondary
outputs, +34V, +15V, +10V,
+5V and -9V normal?
Remove F701 and
check the load side.
Is there short-circuiting?
Is there short-circuiting of
T701 primary side periphery,
Q701, Q703 and S4001?
Replace F701.
Check S4001 and
connection cable.
Is T701's primary oscillator
waveform normal?
Check T701's secondary
load.
Yes
No
No
No
No
Yes
Fluorecent lamp failure to light up
Does F4701 and F4702
function?
Is the pin (34) of IC1201 in
the "H" state?
Is the Q1774 short-circuiting?
Is there short-circuiting of
T1701~T1706 primary side
periphery, Q1701~Q1705?
Yes
Yes
No
No
No
Yes
Replace the fluorecent lamp
with new one and check
again.
Yes
Check the OFL1 line, IC1201
and their peripheral parts.
Check Q1774 and its
peripheral parts.
Check T1701~T1706,
Q1701~Q1705 and
connection cable.
No
Replace F4701 and F4702.
Yes
13
LC-20M4E
TROUBLE SHOOTING TABLE
(Continued)
No picture
Check all the settings microprocessor's adjust process menu.
Is in/output of
IC801 normal?
Is in/output of
IC1201 normal?
Check IC801
and its
peripheral parts.
Check IC1201
and its
peripheral parts.
Check IC402
and its
peripheral parts.
Check IC801,
AV1 line and its
peripheral parts.
Check LCD
panel voltage
and waveform.
Yes
Yes
No
No
No picture
at all
Is in/output of
IC402 normal?
Is input at pin
(73) of IC801
normal?
Yes
No
No
No VIDEO 1
and VIDEO 2
output
Is input at pin
(1) of IC402
normal?
Is the pins (2)
and (4) of IC402
at "L" state?
Check the its
line.
Check the its
line.
Check IC402
and its
peripheral parts.
Is the pins (65)
and (66) of IC2001
at "L" state?
Yes
No
No
Yes
Yes
No VIDEO 1
output
Is input at pin
(5) of IC402
normal?
Is the pin (4) of
IC402 in the
"H" state?
Check the its
line.
Check the its
line.
Yes
Yes
No
No
No VIDEO 2
output
Check IC402
and its
peripheral parts.
Is input at pins
(71) and (72) of
IC801 normal?
No S-VIDEO
output
Check the
SC401, SY-line,
SC-line and their
peripheral parts.
Is the pin (68)
of IC2001 in the
"H" state?
No
LC-20M4E
14
No picture
Check all the settings microprocessor's adjust process menu.
Is source GND
normal?
Is CSCOM
waveform
normal?
Check R1212
and its
peripheral parts.
Check IC1109,
Q1101, Q1102,
D1101, R1120,
R1130 and their
peripheral parts.
Check R1231
and its
peripheral parts.
Yes
No
No
Becomes
dark
No
Time passes,
becomes
dark
Is gate GND
normal?
Is gate clock
(GCK) normal?
Is output at pin
(3) of IC1205
normal?
Yes
No
Check D1201
and its
peripheral parts.
No
Is B-5.5V being
outputted?
Is VCC being
outputted?
Check T701's
secondary +5V
outputs line.
Yes
No
Is GSP
waveform
normal?
Check R1223
and its
peripheral parts.
Yes
No
Check R1223
and gate aray
peripheral parts.
Becomes
white.
Is 3.3V VSH
being
outputted?
Is source clock
(CK) normal?
Check +3.3V
outputs line of
IC781.
Check R1210,
R1211 and their
peripheral parts.
Check FB1203
and gate aray
peripheral parts.
Is output of
LBR and HG
normal?
Yes
Yes
No
No
No
Vertical line
output
TROUBLE SHOOTING TABLE
(Continued)
15
LC-20M4E
No picture
Check all the settings microprocessor's adjust process menu.
Is output of
R0~R5
normal?
Is output of
G0~G5
normal?
Is output of
B0~B5
normal?
Check R1202,
R1203 and their
peripheral parts.
Check R1204,
R1205 and their
peripheral parts.
Check R1206,
R1207 and their
peripheral parts.
Check T701's
secondary +5V
outputs line.
Yes
Yes
No
No
No
Colour is
unusual
Is VLS 5V
being
outputted?
No
Picture
image is
gloomy
Is in/output of
SPIO and
SPOI normal?
Check R1209
and its
peripheral parts.
No
No picture
image
inversion
Is output V0,
V16, V32, V48
and V63
normal?
Check IC1106,
IC1107, IC1108
and their
peripheral parts.
No
Gradation
defect
Is output of U/D
normal?
Check Q1201
and its
peripheral parts.
Yes
No
