Sharp LC-20B2E (serv.man4) Service Manual ▷ View online
12
LC-20B2E
TROUBLE SHOOTING TABLE
No picture, No sound
Check all the settings microprocessor's adjust process menu.
Do F2 and F4 function?
Are T701's secondary
outputs, +38V, +16V, +9V,
+5V and -8V normal?
Remove F2 and F4 and
check the load side.
Is there short-circuiting?
Is there short-circuiting of
T701 primary side periphery,
Q751, Q753 and P901.
Replace F2 and F4.
Check P901 and
connection cable.
Is T701's primary oscillator
waveform normal?
Check T701's secondary
load.
Yes
Yes
No
No
No
No
Yes
Fluorecent lamp failure to light up
Does F1 function?
Is the pin (34) of IC1201 in
the "H" state?
Is the Q3603 short-circuiting?
Is there short-circuiting of
T5701 and T5702 primary
side periphery, Q751~Q753.
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 Q3603 and their
peripheral parts.
Check T5701, T5702,
Q5701~Q5703 and
connection cable.
13
LC-20B2E
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 voltages
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 TV and
VIDEO 1
output
Is voltages at
pin (3) of W7
and pins (3), (4)
and (5) of W14
tuner normal?
Is output at pin
(2) of W7 tuner
normal?
Check the
power line.
Check tuner
and its
peripheral parts.
Is input at pin
(3) of IC402
normal?
Is the pins (2)
and (4) of IC402
at "H" and "L"
state?
Yes
Yes
No
No
No
No
No
Yes
No TV output
Is the pins (65)
and (66) of
IC2001 at "H"
and "L" state?
Yes
Check the its
line.
Check the its
line.
Check IC402
and its
peripheral parts.
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
Yes
No
No
No
No VIDEO 1
output
14
LC-20B2E
TROUBLE SHOOTING TABLE
(Continued)
No picture
Check all the settings microprocessor's adjust process menu.
Is input at pin
(74) of IC801
normal?
Check the AV2
line and their
peripheral parts.
Check the W9,
SY-line, SC-line
and their
peripheral parts.
No
No VIDEO 2
output
Is input at pins
(71) and (72) of
IC801 normal?
No
No S-VIDEO
output
Is input at pin
(70) of IC801
normal?
Check the
V2VO line and
their
peripheral parts.
No
No line
output
Is input at pins
(1), (2), (3), (56),
(57) and (79) of
IC801 normal?
Is output at pins
(11), (13) and
(16) of I4
normal?
Check IC801
and its
peripheral parts.
Check I13 and
its
peripheral parts.
Check I9 and
its
peripheral parts.
Check I4 and
its
peripheral parts.
Is output at pins
(11), (13) and
(16) of I13
normal?
Yes
Yes
No
No
No
No TELETEXT
output
Is output at pins
(44)~(49) of I9
normal?
Yes
No
15
LC-20B2E
TROUBLE SHOOTING TABLE
(Continued)
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?
Check R1223
and gate aray
peripheral parts.
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
Becomes
white.
Is 3.3V VHS
being
outputted?
Is source clock
normal?
Check +3.3V
outputs line of
IC752.
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
Display
