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Model
LC-20M4E (serv.man8)
Pages
50
Size
2.04 MB
Type
PDF
Document
Service Manual
Brand
Device
TV / LCD
File
lc-20m4e-sm8.pdf
Date

Sharp LC-20M4E (serv.man8) Service Manual ▷ View online

LC-20M4E
10
1-3. Counter bias adjustment
Keep off the video input signal.
Place the specified tool at the center of the screen.
Observe the output of the tool on the oscilloscope screen.
Adjust the “COM BIAS” setting on the adjustment process page 2 so that the peak-to-peak level of the waveform
should be minimum.
1-4. White balance adjustment
Feed the NTSC monoscope pattern signal.
Adjust the “RCUTOFF” and “BCUTOFF” settings on the adjustment process page 2 so as to obtain the colour of the
same level as the standard monitor.
Note: For the “RCUTOFF” and “BCUTOFF” settings, keep the readings in the range of -9 to +9. If out of this range, the
user-adjustable range is reduced.
     Adjust them in the indication value range of -9, -7, -5, -3, -1, +1, +3, +5, +7, +9 (odd numbers). When it becomes
even-numbered value (include 0), side favor noise sometimes occurs in the monochrome signal of the specific
gradation.
     Do not change the “GCUTOFF” settings (It also change the black level).
1-5. Factory setting
Set the product’s input mode, picture quality and other factors to their factory setting.
There are the following two ways.
With the keys of the set
In the inspection process mode, hold down both the “SELECT(
)” and “VOL (+)” buttons of the set until “SETTING
COMPLETE” appears on the screen.
Note: Be careful not to turn off the power, release the above two keys and press any other keys until “SETTING
COMPLETE” appears on the screen.
With the adjustment remote controller
With the adjustment remote controller, make the factory settings. Either of the following remote controllers codes
will do.
Calling the Inspection process mode
There are the following two ways.
With the keys of the set
Hold down the “MENU” and “AV INPUT” buttons of the set and turn on the power.
With the adjustment remote controller
Use the inspection process key.
Key name
Remote controller code
Factory setting
100000111111110
Factory setting
100000001010110
E
Changing on-screen display
K
Inspection process mode
Factory setting
Setting complete
SETTING COMPLETE
E
11
LC-20M4E
  1
  > + B – A D J
1 6 0
M O D E L
M 4 E
I N C H   S I Z E
2 0
T I M E R
1
S Y S T E M
A U T O
N T S C   P W M   F R E Q
0 C 0
P A L   P W M   F R E Q
0 B 0
T V   G A I N
O F F
E R R O R   N O   R E S E T
0
P M U T E
0 0
P U B L I C   M O D E O N
C O L O R   S W
2 0 M 4     V E R     1 . 0 0 0
Adjustment process
settings
Microprocessor
version
Adjustment process 
items
Adjustment process page number
2. Lamp error detection
Function
For added safety, this LCD colour TV set has the lamp error detection. The power is automatically turned off if the lamp
or its circuit gets in trouble.
If by any chance there is a problem with the lamp or its circuit, or if the lamp error detection function is activated for any
other reason, the set behaves itself as follows.
1
Even when you switch on the power, the set turns itself off in about 5 seconds. (The power LED indicator on the
front of the set turns from green to red.)
2
If the above action 
1
 occurs 5 times consecutively, the set cannot be switched on. (The power LED indicator stays
in red.)
Correction
Checking with the lamp error detection circuit off
If the lamp error detection fuction is activated to turn off the power LED indicator turns red and the set is now in the
adjustment process mode. In this state, the error detection circuit gets disabled and the power is turned on again.
In so doing, the lamp and its circuit can be checked for anything unusual.
Check to see if “1” or higher value appears in the “ERROR NO RESET” box in the 9th line of the adjustment
process page 1. If so, a lamp error has been detected.
Resetting the lamp error counter
Finally make sure the lamp and its circuit are error-free, and reset the lamp error counter. To do so, select the
“ERROR NO RESET” box in the 9th line of the adjustment process page 1 and enter “0” with the VOL button.
Do the performance check and make sure the lamp error detection functions is not activated.
3. Precautions in making adjustments
In making adjustments, keep the following points in mind.
When you have modified the MODEL and INCH SIZE settings on the process page 1, never turn off the power in
at least 5 seconds. It takes this time to write the E
2
PROM for all the adjustment process parameters of a different
mode. (The cursor does not move for a few seconds when the writing is going on.)  If you have wrongly turned off
the power, once change the MODEL setting to any other model number, wait for 5 seconds, and change the setting
back to the right model number. Then wait for another 5 seconds just to be sure.
To quit the adjustment process mode with adjustments complete, use the ADJUST PROCESS key on the remote
contoller.
4. Adjustment process items
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
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