In the interests of user-safety (Required by safety regulations in some countries) the set should be restored to its
original condition and only parts identical to those specified should be used.
Specifications are subject to change without
prior notice.
1
1
20AR21
20AR31
IMPORTANT SERVICE SAFETY PRECAUTION
Ë
Service work should be performed only b y qualified service technicians who are thoroughly
familiar with all safety checks and the servicing guidelines which follow:
WARNING
1. For continued safety, no modification of any circuit
should be attempted.
2. Disconnect AC power before servicing.
3. Semiconductor heat sinks are potential shock
hazards when the chassis is operating.
4. The chassis in this receiver has two ground systems
which are separated by insulating material. The nonisolated (hot) ground system is for the B+ voltage
regulator circuit and the horizontal output circuit. The
isolated ground system is for the low B+ DC v oltages
and the secondary circuit of the high voltage
transformer.
To prevent electrical shock use an isolation
transformer between the line cord and power
receptacle, when servicing this chassis.
SERVICING OF HIGH VOLTAGE SYSTEM
AND PICTURE TUBE
When servicing the high voltage system,
remove the static charge by connecting a
10k ohm resistor in series with an insulated
wire (such as a test probe) between the picture tube ground and the anode lead. (AC
line cord should be disconnected from AC
outlet.)
1. Picture tube in this receiver employs integr al implosion
protection.
2. Replace with tube of the same type number for
continued safety.
3. Do not lift picture tube by the neck.
4. Handle the picture tube only when wearing
shatterproof goggles and after discharging the high
voltage anode completely.
X-RADIATION AND HIGH VOLTA GE LIMITS
1. Be sure all service personnel are aware of the
procedures and instructions covering X-radiation. The
only potential source of X-ray in current solid state
TV receivers is the picture tube. Howe ver , the picture
tube does not emit measurable X-Ray radiation, if
the high voltage is as specified in the "High Voltage
Check" instructions.
It is only when high voltage is excessive that Xradiation is capable of penetrating the shell of the
picture tube including the lead in the glass material.
The important precaution is to keep the high voltage
below the maximum level specified.
2. It is essential that ser vicemen have available at all
times an accurate high voltage meter.
The calibration of this meter should be checked
periodically.
3. High voltage should always be kept at the rated v alue
−no higher. Operation at higher voltages may cause
a failure of the picture tube or high voltage circuitry
and;also, under certain conditions, may produce
radiation in exceeding of desirable levels.
4. When the high voltage regulator is operating properly
there is no possibility of an X-radiation problem. Every
time a color chassis is serviced, the brightness should
be tested while monitoring the high voltage with a
meter to be certain that the high voltage does not
exceed the specified value and that it is regulating
correctly.
5. Do not use a picture tube other than that specified or
make unrecommended circuit modifications to the
high voltage circuitry.
6. When trouble shooting and taking test measurements
on a receiver with excessiv e high voltage, av oid being
unnecessarily close to the receiver.
Do not operate the receiver longer than is necessary
to locate the cause of excessive voltage.
2
22
IMPORTANT SERVICE SAFETY PRECAUTION
(Continued)
20AR21
20AR31
BEFORE RETURNING THE RECEIVER
(Fire & Shock Hazard)
Before returning the receiver to the user, perform
the following safety checks.
1. Inspect all lead dress to make certain that leads are
not pinched or that hardware is not lodged between
the chassis and other metal parts in the receiver.
2. Inspect all protective devices such as non-metallic
control knobs, insulating materials, cabinet backs,
adjustment and compartment covers or shields,
isolation resistor-capacity networks, mechanical
insulators and etc.
3. To be sure that no shock hazard exists, check for
leakage current in the following manner.
• Plug the AC cord directly into a 110~220 volt AC
outlet, (Do not use an isolation transformer for this
test).
• Using two clip leads, connect a 1.5k ohm, 10 watt
resistor paralleled by a 0.15µF capacitor in series with
all exposed metal cabinet parts and a known earth
ground, such as electrical conduit or electrical ground
connected to earth ground.
• Use an AC voltmeter ha ving with 5000 ohm per v olt,
or higher, sensitivity to measure the A C v oltage drop
across the resistor.
• Connect the resistor connection to all exposed metal
parts having a return to the chassis (antenna, metal
cabinet, screw heads, knobs and control shafts,
escutcheon and etc.) and measure the AC voltage
drop across the resistor.
AII checks must be repeated with the AC ine cord
plug connection reversed. (If necessary, a nonpolarized adapter plug must be used only for the
purpose of completing these check.)
Any current measured must not exceed 0.5 milliamp .
Any measurements not within the limits outlined
above indicate of a potential shock hazard and
corrective action must be taken before returning the
instrument to the customer.
Many electrical and mechanical parts in television
receivers have special safety-related characteristics.
These characteristics are often not evident from visual
inspection, nor can protection afforded by them be
necessarily increased by using replacement components
rated for higher voltage, wattage, etc.
Replacement parts which have these special safety
characteristics are identified in this manual; electrical
components having such features are identified by " å"
and shaded areas in the Replacement Parts Lists and
Schematic Diagrams.
For continued protection, replacement parts must be
identical to those used in the original circuit. The use of
substitute replacement parts which do not have the same
safety characteristics as the factory recommended
replacement parts shown in this service manual, may
create shock, fire, X-radiation or other hazards.
3
20AR21
20AR31
LOCATION OF USER'S CONTROL
Front Panel
MTS STER EO
AUTO VOLTA GE
POWER
Press On.
Press again Off.
SENSOR
REMOTE CONTROL
AREA FOR
Basic Remote Control Functions
POWER
Press On.
Press again Off.
REMOTE KEYPAD
Accesses any channel from keypad.
RETURN
Returns to previous channel.
VOLUME UP/DOWN
(+) Increases sound.
(–) Decreases sound.
• In menu mode, changes or selects
the TV adjustments.
MUTE
Press Mutes sound.
Press again Restores sound.
• CLOSED CAPTION appears when
sound is muted.
VOLUME UP/DOWN
( ) Increases sound.
( ) Decreases sound.
MENU
Press Accesses MAIN MENU.
Press again Exits MAIN MENU.
RETURN
CT-818
(20AR21)
VIDEO/AUDIO TERMINALS
(VIDEO/AUDIO terminals are also
provided on the rear.)
(20AR31)
VIDEO/AUDIO TERMINALS
CHANNEL UP/DOWN
( ) Selects next higher channel.
( ) Selects next lower channel.
Infrared Transmitter Window
INPUT
Press Switch to external video input
mode.
Press again Switch to TV mode.
(20AR31)
Press Switch to external video
INPUT 1 mode.
Press 2 times Switch to external
video INPUT 2 mode.
Press 3 times Switch back to the
original TV mode.
CHANNEL UP/DOWN
( ) Selects next higher channel.
( ) Selects next lower channel.
• Moves the “
screen.
MENU
Press Accesses MAIN MENU.
Press again Exits MAIN MENU.
DISPLAY
Press Displays receiving channel for
4 seconds.
Press again Removes display.
• Temporarily displays receiving
channel when in Closed Caption
mode.
” mark of the MENU
4
INSTALLATION AND SERVICE INSTRUCTIONS
Note:(1)When performing any adjustments to resistor controls and transformers use non-metallic
screwdrivers or TV alignment tools.
(2)Before performing adjustments, the TV set must be on at least 15 minutes.
20AR21
20AR31
CIRCUIT PROTECTION
The receiver is protected by a 3.15A fuse (F701),
mounted on PWB-A, wired into one side of the AC
line input.
+B DC REGULATOR CONFIRMATION
The + B DC output voltage adjustment is not included
in this circuit.However, should confirmation be
reguired proceed as follows.
1. Actuate receiver with 220V AC input voltage.
2. Receive a local channel.
3. Connect positive lead of digital voltmeter to C754
positive side on PWB-A ; negative lead to chassis
ground.
4. Confirm this voltage reading is as below.
CAUTION: The reading should be within +130.0 ± 2.0V
DC to ensure normal function and circuitry
reliability.
X-RADIATION PROTECTOR CIRCUIT TEST
After service has been performed on the horizontal
deflection system, high v oltage system, B+ system,
test the X-Radiation protection circuit to ascertain
proper operation as follows:
HIGH VOLT A GE CHECK
High voltage is not adjustable but must be checked
to verify that the receiver is operating within safe
and efficient design limitations as specified checks
should be as follows:
1. Connect an accurate high voltage meter between
ground and anode of picture tube.
2. Operate receiver for at least 15 minutes at 110~220V
AC line voltage, with a strong air signal or a properly
tuned in test signal.
3. Receve a good local channel.
4. The voltage should be approximately, 25.5kV (at
pictuer MAX Bright center condition).
If a correct reading cannot be obtained, check circuitry
for malfunctioning components.
1. Apply 220V AC using a variac transf ormer for accurate
input voltage.
2. Allow for warm up and adjust all customer controls
for normal picture and sound.
3. Receive a good local channel.
4. Connect a digital voltmeter to TP653 and make sure
that the voltmeter reads 21.4 ± 1.5 V.
5. Apply external 27.9V DC at TP653 by using an
external DC supply, TV must be shut off.
6. To reset the protector, unplug the AC cord and make
a short circuit between TP651 and TP652. No w make
sure that normal picture appears on the screen.
7. If the operation of the hor izontal oscillator does not
stop in step 5, the circuit must be repaired before the
set is returned to the customer.
5
20AR21
20AR31
For adjustments of this model, the bus data is conver ted to various analog signals by the D/A converter
circuit.
Note: There are still a few analog adjustments in this series such as focus and master screen voltage.
Follow the steps below whenever the service adjustment is required. See "Table-B" to determine, if service adjustments are required.
1. Service mode
Before putting unit into the service mode, check that
customer adjustments are in the normal mode. Use
the reset function in the video adjustment menu to
ensure customer controls are in their proper (reset)
position.
2. Service item selection
Once in the service mode, press the Ch-up or Chdown button on the remote controller or at the set.
The service adjustment item will vary in increments
of one. Select the item you wish to adjust.
3. Data number selection
Press the Vol-up or down button to adjust the data
number.
To enter the ser vice mode and exit service mode.
Short JA137&JA138 for 1 Second and release to switch
to the service mode position, and the microprocessor is
in input mode.(Adjustment through the I2C bus control.)
To exit the service mode, turn the television off by
pressing the power button.
SERVICE ADJUSTMENT ITEM
Figure A.
DATA NUMBER
25AGC:
6
SERVICE MODE
(1) In the Service Mode, Key is used to select the mode in the following oreder.
AGC &WHITE POINTSUB
GEOMETRICADJ.ADJ.
MODEMODEMODE
FEATUREICMTS
OPTIONOPTIONADJ.
MODEMODEMODE
20AR21
20AR31
OFFSET
ADJ.
MODE
AGC &
GEOMETRIC
MODE
AGC TAKE OVER POINT (AGC)
VERTICAL SLOPE (V-LIN)
VERTICAL AMP (V-AMP)
VERTICAL SHIFT (V-CENT)
VERTICAL ZOOM (V-ZOOM)
HORIZONTAL SHIFT (H-CENT)
EAST-WEST WIDTH (H-SIZE)
HORIZONTAL PARALLELOGRAM (EW//)
EAST-WEST PARABOLA / WIDTH (PARA)
EAST-WEST UPPER CORNER
PARABOLA (COR(U))
EAST-WEST LOWER CORNER
PARABOLA (COR(L))
EAST-WEST TRAPEZIUM (TRAPE)
HORIZONTAL BOW (HB)
S-CORRECTION (S-COR)
↓
↓
↓
↓
↓
↓
↓
↓
↓
↓
↓
↓
↓
↓
WHITE POINT
ADJ.
MODE
W.P. RED OFFSET HIGH /
OFFSET BLUE TONE (DRI-R-HI)
W.P. GREEN OFFSET HIGH /
OFFSET BLUE TONE (DRI-G-HI)
W.P.BLUE OFFSET HIGH /
OFFSET BLUE TONE (DRI-B-HI)
W.P. RED MH / STD (DRI-R-MH)
W.P. GREEN MH / STD (DRI-G-MH)
W.P. BLUE MH / STD (DRI-B-MH)
W.P. RED OFFSET ML /
OFFSET RED TONE (DRI-R-ML)
W.P. GREEN OFFSET ML /
OFFSET RED TONE (DRI-G-ML)
W.P. BLUE OFFSET ML /
OFFSET RED TONE (DRI-B-ML)
W.P. RED OFFSET LOW (DRI-R-LO)
W.P. GREEN OFFSET LOW (DRI-G-LO)
W.P. BLUE OFFSET LOW (DRI-B-LO)
↓
↓
↓
↓
↓
↓
↓
↓
↓
↓
↓
↓
SUB
ADJ.
MODE
MAX VOLUME (SUB-VOL)
SUB CONTRAST (SUB-CON)
SUB TINT (SUB-TINT)
SUB COLOUR (SUB-COL)
SUB BRIGHTNESS (SUB-BRI)
SUB SHARPNESS (SUB-SHP)
MAX HOTEL VOLUME (HTL-VOL)
HOTEL PROGRAM NO(HTL-PRG)
BLUE BACK CONTRAST (BB-CON)
OSD GRB REFERENCE (RGB)
BLACK LEVEL OFFSET R(CUT-R)
BLACK LEVEL OFFSET G(CUT-G)
CATHODE DRIVE LEVEL(CDL)
↓
↓
↓
↓
↓
↓
↓
↓
↓
↓
↓
↓
↓
7
20AR21
20AR31
OFFSET
ADJ.
MODE
Y-D TIME (TV) [ YD ] (DL-TV)
Y-D TIME (AV) [ YD ] (DL-AV)
INITIAL/DEFAULT LANGUAGE (INIT)
FA O-MAX V OLUME (FA O-V OL)
ENERGY SAVE OFFSET (ESV_OFFS)
CLOSE CAPTION POSITION (CCPOS)
↓
↓
↓
↓
↓
↓
IC
OPTION
MODE
VERTICAL SCAN DISABLE (VSD)
BLACK STRETCH (BKS)
AUTOMATIC VOLUME LEVELLING (AVL)
FAST FILTER IF-PLL ( FFI )
ENABLE VERTICAL GUARD ( EVG )
EHT TRACKING MODE ( EHT )
OVERSCAN SWITCH OFF (OSO)
AUTO COLOUR LIMIT (ACL)
FORCED COLOUR-ON (FCO)
VIDEO MUTE AT IDENT LOSS (VMI)
VIDEO MUTE AT PROGRAM/SOURCE CHANGE (VMC)
HOTEL MODE (HTL)
GAIN FM DEMODULATOR (BTSC)
CHARGE PUMP (CP)
FM WINDOW SELECTION (FMWS)
SOUND MUTE BIT 0 (SM0)
SOUND MUTE BIT 1 (SM1)
IF AGC SPEED BIT 0 (AGC0)
IF AGC SPEED BIT 1 (AGC1)
PHI 1 TIME CONSTANT FOR FE (FOA-FE)
PHI 1 TIME CONSTANT FOR FE (FOB-FE)
PHI 1 TIME CONSTANT FOR AV (FOA-AV)
PHI 1 TIME CONSTANT FOR AV (FOB-AV)
DYNAMIC SKIN CONTROL (DSK)
RATIO PRE- AND OVERSHOOT BIT 0 (RPO0)
RATIO PRE- AND OVERSHOOT BIT 1 (RPO1)
GAIN FM DEMODULATOR (AGN)
AUTO SWITCH OFF ENABLED (AUTO-OFF)
↓
↓
↓
↓
↓
↓
↓
↓
↓
↓
↓
↓
↓
↓
↓
↓
↓
↓
↓
FORWARD : CH DOWN KEY
REVERSE : CH UP KEY
( ) means OSD display.
Figure B: ADJUSTMENT CATEGORIES
1Press the CH DOWN/UP key on the remote controller to get ready to select the mode one by one.
2Press the CH DOWN/UP key on the remote controller to select the modes reversibly one by one.
3Using the VOLUME UP/DOWN key on the remote controller, the data can be modified.
(OSD disturbance can be erased by R/C display key)
8
SERVICE MODE
20AR21
20AR31
SERVICE
POSITION
AGCAGC TAKE OVER POINT0~6314ADJ
V-LINVERTICAL SLOPE0~6332ADJ
V-AMPVERTICAL AMP0~6332ADJ
V-CENTVERTICAL SHIFT0~6332ADJ
V-ZOOMVERTICAL ZOOM0~6332FIX
H-CENTHORIZONTAL SHIFT0~6332ADJ
H-SIZEEAST-WEST WIDTH0~6332FIX
EW//HORIZONTAL PARALLELOGRAM0~6332FIX
PARAEAST-WEST PARABOLA / WIDTH0~6332FIX
COR(U)EAST-WEST UPPER CORNER PARABOLA0~6332FIX
COR(L)EAST-WEST LOWER CORNER PARABOLA0~6332FIX
TRAPEEAST-WEST TRAPEZIUM0~6332FIX
HBHORIZONTAL BOW0~6332FIX
S-CORS-CORRECTION0~630FIXmust be "17"
DRI-R-HI“W,P RED OFFSET HIGH / OFFSET BLUE TONE”0~6332FIXmust be "32"
DRI-G-HIW.P. GREEN OFFSET HIGH / OFFSET BLUE TONE0~6332FIXmust be "33"
DRI-B-HIW.P.BLUE OFFSET HIGH / OFFSET BLUE TONE0~6332FIXmust be "37"
DRI-R-MHW.P. RED MH / STD0~6325FIXmust be "32"
DRI-G-MHW.P. GREEN MH / STD0~6332ADJ
DRI-B-MHW.P. BLUE MH / STD0~6332ADJ
DRI-R-MLW.P. RED OFFSET ML / OFFSET RED TONE0~6332FIXmust be "32"
DRI-G-MLW.P. GREEN OFFSET ML / OFFSET RED TONE0~6332FIXmust be "32"
DRI-B-MLW.P. BLUE OFFSET ML / OFFSET RED TONE0~6332FIXmust be "25"
DRI-R-LOW.P. RED OFFSET LOW0~6332FIXmust be "32"
DRI-G-LOW.P. GREEN OFFSET LOW0~6332FIXmust be "22"
DRI-B-LOW.P. BLUE OFFSET LOW0~6332FIXmust be "19"
SUB-VOLMAX VOLUME0~6363FIXmust be "63"
SUB-CONSUB CONTRAST0~6363FIXmust be "54"
SUB-COLSUB COLOUR0~6332ADJ
SUB-BRISUB BRIGHTNESS0~6332ADJ
SUB-TINTSUB TINT0~6332ADJ
SUB-SHPSUB SHARPNESS0~6332FIXmust be "27"
HTL-VOLMAX HOTEL VOLUME0~6332FIX
HTL-PRGHOTEL PROGRAM NO0~125 or >125 for none255FIX
BB-CONBLUE BACK CONTRAST0~1510FIXmust be "5"
RGBOSD GRB REFERENCE0~1515FIXmust be "5"
CUT-RBLACK LEVEL OFFSET R0~6332ADJ
CUT-GBLACK LEVEL OFFSET G0~6332ADJ
CDLCATHODE DRIVE LEVEL0~150FIXmust be "6"
DL-TVY-D TIME (TV) [ YD ]0~1512FIXmust be "2"
DL-AVY-D TIME (AV) [ YD ]0~1512FIXmust be "8"
INITINITIAL/DEFAULT LANGUAGE0(English), 1(Spanish),0FIXmust be "1"
FMWSFM WINDOW SELECTION0(disable) or1(enable)0FIX
SM0SOUND MUTE BIT 0 (SM0)0(disable) or1(enable)1FIX
SM1SOUND MUTE BIT 10(disable) or1(enable)0FIX
AGC0IF AGC SPEED BIT 00(disable) or1(enable)1FIX
AGC1IF AGC SPEED BIT 10(disable) or1(enable)0FIX
FOA-FEPHI 1 TIME CONSTANT FOR FE0(disable) or1(enable)0FIX
FOB-FEPHI 1 TIME CONSTANT FOR FE0(disable) or1(enable)0FIX
FOA-AVPHI 1 TIME CONSTANT FOR AV0(disable) or1(enable)1FIX
FOB-AVPHI 1 TIME CONSTANT FOR AV0(disable) or1(enable)1FIX
FSLFORCED SLICING LEVEL FOR VERTICAL SYNC.0(disable) or1(enable)0FIX
HP2SYNCHRONISATION OF OSD/TEXT DISPLAY0(disable) or1(enable)0FIX
RGBLRGB BLANK0(disable) or1(enable)0FIX
V-CHIPV-CHIP0(disable) or1(enable)0FIX
MTS MTS DECODING ENABLED 0(disable) or1(enable) 0 FIX*
DEMODEMO MODE0(disable) or1(enable)1FIX
CLOCKREAL TIME CLOCK / ON TIMER0(disable) or1(enable)1FIXmust be "1"
E-SAVEENERGY SAVE0(disable) or1(enable)1FIX
P_PREFPERSONAL PREFERENCE PROGRAM0(disable) or1(enable)0FIX
UNIV+UNIVERSAL PLUS0(disable) or1(enable)0FIX
SPEAKERSPEAKER ON/OFF0(disable) or1(enable)0FIX
FAOFIXED AUDIO OUT0(disable) or1(enable)0FIX
VIEW-TMVIEW TIMER0(disable) or1(enable)1FIXmust be "1"
FRENCHFRENCH LANGUAGE0(disable) or1(enable)0FIX
EZ-SETUPEZ SETUP / AUTOPRESET0(AUTOPRESET) or1FIX
W-TEMPWHITE TEMP OR FAVORITE COLOR0(FC) or 1(WT)0FIX
AVAV ENABLED OR DISABLED0(without ext. source) or0FIX
AV2 AV2 ENABLED OR DISABLED 0(1 input) or 1(2 input) 0 FIX*
DSKDYNAMIC SKIN CONTROL0(disable) or1(enable)0FIX
RPO0RATIO PRE- AND OVERSHOOT BIT 00(disable) or1(enable)0FIX
RPO1RATIO PRE- AND OVERSHOOT BIT 10(disable) or1(enable)0FIX
AGNGAIN FM DEMODULATOR0(normal) or1(+6dB)0FIX
AUTO-OFFAUTO SWITCH OFF ENABLED0(disable) or1(enable)1FIX
PON-CH0(disable) or1(enable)0FIX
ADJUST ITEM
RANGE
1(EZ SETUP)
1(with external source)
DATA
INITIAL VALUE
FIX/ADJ
REMARK
20AR21→0/20AR31→1
20AR21→0/20AR31→1
Table - A
Holding down to short JA137 & JA138 and turn on the main power SW will automatically write the initial values into
IC1003.
This is only can done when a new EEPROM is used. (Judge with the first 4 bytes.)
PART REPLACED
IC801
IC1003
CRT
NECESSARY
ADJUSTMENT
X
X
UNNECESSARY
X
NOTES
Data is stored in IC1003.
Holding down to short JA137 & JA138 and turn on the main
power SW will automatically write the initial values into IC1003.
This is only can done when a new EEPROM is used. (Judge
with the first 4 bytes.)
Adjust items related to picture tube only.
Table - B
10
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