Sharp 20CT-250 User manual

20CT-250
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.
The chassis in this receiver is partially hot. Use an isolation transformer between the line cord plug and power
receptacle, when servicing this chassis.
Topreventelectricshock,donotremovecover. Nouser–serviceablepartsinside. Referservicingtoqualified
service personnel.
WARNING
20CT-250
FEATURE
»SPECIFICATIONS...............................................2
»IMPORTANTSERVICE NOTES ......................... 2
»ADJUSTMENT PRECAUTIONS ........................ 3
»SERVICE ADJUSTMENT................................... 6
»TROUBLESHOOTINGTABLE......................... 15
»SOLID STATE DEVICE BASE DIAGRAM ........ 18
Page
CONTENTS
Page
SHARP CORPORATION
ËFull Auto Channel Preset And Auto Channel Skip
Ë100 CH Program Memory
ËAperture Control Circuit
ËBlack Stretch Circuit
ËBilingual System (Mono)
ËAuto Channel Scan System
ËFavorite Channel Memory System
COLOURTELEVISION
Chassis No. G2
SERVICE MANUAL
S88U521CT-250
»CHASSISLAYOUT............................................17
»SCHEMATIC DIAGRAM ................................... 19
»BLOCK DIAGRAM ............................................23
»PRINTED WIRING BOARD ASSEMBLIES ...... 25
»REPLACEMENT PARTS LIST.......................... 27
MODEL
ËUser Preset Timer (On Timer/Sleep Timer/Reminder)
Ë2 Selectable OSD Languages (English/Thai)
ËCATV (Hyper Band) Ready
〈Used Frequency Synthesizer Tuner〉
ËNTSC 4.43/3.58MHz (AV only), Rear AV IN/OUT
terminal
ËBlue Back Noise Mute
ËFine Tuning Adjustable with Remote Control

2
2-1 2-2
20CT-250
IMPORTANT SERVICE NOTES
Maintenance and repair of this receiver should be done by
qualified service personnel only.
SERVICING OF HIGH VOLTAGE SYSTEM AND
PICTURE TUBE
When servicing the high voltage system, remove static charge from it by
connecting a 10k ohm Resistor in series with an insulated wire (such as a
test probe) between picture tube dag and 2nd anode lead. (AC line cord
should be disconnected from AC outlet.)
1. Picture tube in this receiver employs integral 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 completely
X-RAY
This receiver is designed so that any X-Ray radiation is kept to an absolute
minimum. Since certain malfunctions or servicing may produce potentially
hazardous radiation with prolonged exposure at close range, the following
precautions should be observed:
1. When repairing the circuit, be sure not to increase the high voltage to more than 24.5
kV (at beam 0 µA) for the set.
2. To keep the set in a normal operation, be sure to make it function on 22.0 kV ±1.5 kV (at
beam 800 µA) in the case of the set. The set has been factory –Adjusted to the above-
mentioned high voltage.
If there is a possibility that the high voltage fluctuates as a result of the repairs, never
forget to check for such high voltage after the work.
3. Do not substitute a picture tube with unauthorized types and/or brands which may cause
excess X-ray radiation.
BEFORE RETURNING THE RECEIVER
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 fishpapers,
cabinet backs, adjustment and compartment covers or shields, isolation resistor-
capacity networks, mechanical insulators etc.
SPECIFICATIONS
Convergence.................................................................... Self Converging System
Focus .........................................................................Uni Bi-Potential Electrostatic
Sweep Deflection ..................................................................................... Magnetic
Intermediate Frequencies
Picture IF Carrier ................................................................................. 38.9 MHz
Sound IF Carrier Frequency ...................................................... 33.16/33.4 MHz
Colour Sub-Carrier Frequency .............................................................. 34.47 MHz
PowerInput ........................................................................220-240V AC 50/60 Hz
Power Consumption ........................................................................................ 80W
Audio Power Output Rating ........................................................................... 3.0 W
(at Max.)
Speaker
Size .....................................................................................................10 cm pcs
Voice Coil Impedance..............................................................8 ohms at 400 Hz
Aerial Input Impedance
VHF/UHF.............................................................................75 ohm Unbalanced
Receiving System .............................................................CCiR SECAM/PAL B, G
NTSC 3.58/4.43 MHz (AV Input Only)
Tuner Ranges
»VHF-Channels ................................. E2 (48.25 MHz) thru E12 (224.25 MHz)
»UHF-Channels ............................. E21 (471.25 MHz) thru E69 (855.25 MHz)
Dimensions ................................................................................. Width: 690.0 mm
Height: 462.5 mm
Depth: 481.0 mm
Weight (approx.): 20.2 kg
Cabinet Material.................................................................................... All Plastics
Specifications are subject to change without prior notice.

3
3-1 3-2
20CT-250
ADJUSTMENT PRECAUTIONS
This model’s settings are adjusted in two different ways: through the I2C bus control and in the conventional analog
manner. The adjustment via the I2C bus control includes preset-only items and variable data.
1. Calling the service mode by the microprocessor
1Set the switch S1006 to the service mode position, and the microprocessor is put in the service mode
(adjustment through the I2C bus control).
2Press the CH UP/DOWN keys on the remote controller to select the modes one by one.
3Press the CH UP/DOWN keys on the remote controller to select the modes in the order opposite to the
above step 2.
4Using the VOLUME UP/DOWN keys on the remote controller, the data can be modified.
5Set the switch S1006 to the normal mode (OFF) position, and the microprocessor is put out of the
service mode.
2. Factory presettings
1Set the switch S1006 to the service mode position and turn on the main power switch. Initial values are
automatically preset only when a new E2PROM is used (judgment with the first 4 bytes).
2The initial data are preset as listed on page 5.
3Keep in mind that some settings should be modified, and the others should remain as preset.
Note: Once the chassis has been put together, be sure to set the switch S1006 to the service mode
position first and then turn on the main power switch (see the step 2.-1above). Turning on
the power without initializing the E2PROM may cause a flow of excess beam current.
3. The accompanying memory map (11-page document for the RH-iX3031CE ) is for your
reference.

4
4-1 4-2
20CT-250
User data
CONTRAST MAX (64/64)
COLOUR CENT (32/64)
BRIGHTNESS CENT (32/64)
TINT CENT (32/64)
SHARPNESS CENT (32/64)
S-VOLUME MIN (1/64)
BLUE BACK OFF
* When the modes are switched, the last service mode data are stored into the E2PROM.
* In the service mode, the user data are preset as follows.
Mode Key input
H-CENTER 50 PICTURE
V-CENTER 50 TEXT
V-AMP 50 INDEX
V S CORR 50 RED
V-LINE 50 GREEN
SUB CONT CANCEL
Y SUB CONT REVEAL
SUB COLOUR TIMEDPAGE
SUB BRIGHT SIZE
SUB TINT HOLD
SUB SHARP RESET
R-Y YELLOW
B-Y CYAN
A/V 1/2 SKIP
VIDEO MUTE BLUE BACK
* The following keys are used to go directly to their respective modes.
SERVICE MODE
(1) Press the specific keys to change the modes as follows.
In the direction of arrow : CH DOWN key
In the opposite direction : CH UP key
RASTER mode
R-CUT OFF
G-CUT OFF
B-CUT OFF
KEY
R-CUT OFF
G-CUT OFF
B-CUT OFF
R-DRIVE
B-DRIVE
LATERAL mode
V-AMP 50 Hz (V-AMP50)
V-LINE 50 Hz (V-LINE50)
S-CORRECT 50 Hz (V S-CORR50)
V-PHASE 50 Hz (V-CENTER50)
H-PHASE 50 Hz (H-CENTER50)
V-BLK START (V-BLK ST50)
V-BLK STOP (V-BLK SP50)
UP
1 KEY
2 KEY
3 KEY
7 KEY
8 KEY
DOWN
4 KEY
5 KEY
6 KEY
F/B KEY
0 KEY
CUT-OFF/
BKGD mode
LATERAL mode
R-DRIVE
B-DRIVE
CUT-OFF mode
50 Hz ADJUST mode COLOUR ADJUST mode
50 Hz ADJUST mode COLOUR ADJUST mode
Y-DY/OP ADJUST mode 60 Hz ADJUST mode SUB-ADJUST mode
In the direction of arrow : CH DOWN key
In the opposite direction : CH UP key
CUT-OFF/BKGD mode
3-sec time out3-sec time out
3-sec time out3-sec time out
9 KEY
In the direction of arrow : CH DOWN key
In the opposite direction : CH UP key
* The characters in parentheses appear on the on-screen display.
SECAM R-Y (R-Y)
SECAM B-Y (B-Y)
SUB CONTRAST (SUB CON)
SUB BRIGHT (SUB BRI)
SUB COLOUR (SUB COL)
SUB SUBTINT ( SUB TIN)
SUB SHARPNESS (SUB SHARP)
Y-SUB CONTRAST (Y SUB CON)
SUB-ADJUST mode
V-AMP 60 Hz (V-AMP60)
V-LINE 60 Hz (V-LINE60)
VS-CORRECT 60 Hz
V-PHASE 60 Hz (V-CENTER60)
H-PHASE 60 Hz (H-CENTER60)
V-BLK START 60 Hz (V-BLK ST60)
V-BLK STOP 60 Hz (V-BLK SP60)
60Hz ADJUST mode
Y DELAY PAL (DT PAL TV/AV)
Y DELAY SECAM (ST SECAM TV/AV)
Y DELAY NTSC (DT NTSC TV/AV)
Y DELAY B/W (DT BW TV/AV)
VIDEO MUTE ON/OFF (V-MUTE)
VIDEO 2 ON/OFF (AV2)
(DELAY A/V effective in A/V mode)
Y-DY/OPTION mode
In the direction of arrow : CH DOWN key
In the opposite direction : CH UP key
* The characters in parentheses
appear on the on-screen display.

5
5-1 5-2
20CT-250
INITIAL SETTINGS OF CHANNEL SELECTION DATA
(1) Make an entry of MCL1 in the service mode in order to set the following channel selection data to the
E2PROM. And select the POS1 channel. (An MCL2, -3 or -4 input makes different settings.)
*To go to the service mode, the data at the E2PROM’s addresses 00H thru 03H are read. If the data are not as
given below, the E2PROM is initialized according to the table below.
Address: Data
00H : 23H 02H : 13H
01H : 20H 03H : 61H
E2PROM item Data adjustable range Data initial value Remarks
(00H) –––––––––– 23H
(01H) –––––––––– 20H
(02H) –––––––––– 13H
(03H) –––––––––– 61H
R CUT OFF 0 ~255 0
G CUT OFF 0 ~255 0
B CUT OFF 0 ~255 0
G DRIVE 0 ~255 127
B DRIVE 0 ~255 127
50Hz V-AMP 0 ~127 58
50Hz V-LINEARITY 0 ~31 16
50Hz S-CORRECTION 0 ~127 67 *1
50Hz V-PHASE 0 ~75–3*1
50Hz H-PHASE 0 ~31 7 +5 *1
V-BLK ST 50 0 ~63 58→63 (50Hz)
V-BLK SP 50 0 ~127 25
60HzV-AMP 0 ~127 59
60HzV-LINEARITY 0 ~31 14
60Hz S-CORRECTION 0 ~127 74 *2
60Hz V-PHASE 0 ~72 *4
60Hz H-PHASE 0 ~31 12
60Hz V BLK ST 0 ~63 60→63 (60Hz)
60Hz V BLK SP 0 ~127 20
SECAM R-Y 0 ~15 10
SECAM B-Y 0 ~15 6
SUB-CONTRAST 0 ~255 255 *2
SUB-BRIGHT 0 ~255 127
SUB-COLOUR 0 ~255 110
SUB-TINT 0 ~127 70
SUB-SHARPNESS 0 ~63 28
Y SUB-CONTRAST 0 ~31 18 *2
DT PAL TV/AV 0 ~7 2/2 *2
DT SECAM TV/AV 0 ~7 4/4 *2
DT NTSC TV/AV 0 ~7 2/2 *2
DT B/W TV/AV 0 ~7 2/2 *2
V-MUTE ON/OFF OFF
A/V 2 1/2 1
NVM With all the adjustments complete, do not change the data of addresses 00H thru 03H. Other-
wise the E2PROM will be initialized when the AC power is turned on.
*1 : These data are additionally adjusted for 60Hz based on the 50Hz settings.
*2 : Unless otherwise specified, these data are fixed and need no adjustment.
*4 : Only 0 through 5 must be used in changing the data.
POS RECEPTION FREQ (MHZ) S-SYSTEM
1 48.25 B/G
2 62.25 B/G
3 77.25 D/K
4 175.25 B/G
5 182.25 B/G
6 183.25 D/K
7 191.25 D/K
8 196.25 D/K
9 210.25 B/G
10 224.25 B/G
11 471.25 B/G
12 487.25 I
13 503.25 B/G
14 575.25 B/G
15 599.25 B/G
16 621.25 –
17 639.25 D/K
18 703.25 B/G
19 735.25 I
20 767.25 B/G
POS RECEPTION FREQ (MHZ) S-SYSTEM
21 815.25 B/G
22 855.25 I
23 855.25 B/G
24 55.25 B/G
25 83.25 B/G
26 183.25 –
27 193.25 –
28 471.25 B/G
29 477.25 –
30 693.25 –
31 885.25 B/G
32 112.25 B/G
33 168.25 B/G
34 FREE –
35 294.25 B/G
36 463.25 B/G
37 FREE –
38 647.25 B/G
39 663.25 B/G
40 679.25 B/G
FACTORY SETTING
(1) The following key-in data have been factory-set for the E2PROM.
Item Setting
SKIP OFF
AFT ON
C-SYSTEM AUTO
S-SYSTEM B/G
LAST POWER ON
LAST TV/AV TV
DIGIT 1DIG
LANGUAGE THAI
BLUE BACK ON
LAST POS 1
LAST FB POS 1
VOLUME MIN
CONTRAST MAX
COLOUR CENT
BRIGHTNESS CENT
TINT CENT
SHARPNESS CENT

6
6-1 6-2
20CT-250
PIF/AFT/AGC ADJUSTMENT
No. Adjusting point Adjusting procedure/conditions Waveform and others
VCO adjust-
ment: T203 1. Disconnect the antenna from the tuner antenna terminal.
2. Apply DC voltage to pin (4) of IC201 (IF AGC).
»DC voltage: 6.0 V (allowable +0.1 V)
3. Using a digital voltmeter, measure the DC volt-
age at pin (20)(PLL FIL) of IC201.
* The digital voltmeter must be able to take read-
ings down to the third decimal place.
4. Relieve pin (4) of IC201 of the DC voltage.
5. Reconnect the antenna in position and receive
the E-12CH signal. (With the AFT off, adjust the
receiving frequency to 224.25 MHz.)
6. Connect the DC digital voltmeter to pin (20) of
IC201. Adjust T203 so that the voltmeter should
read the same voltage as in Step 3.
Allowable error : 0.015 V (20 kHz)
1* Warm upthe unitfor longerthan
10 minutes in advance.
* 10 kHz at about 0.007 V.
* Position the T203 core in the
range in which the Colour Bar
signal can be received.
AFT
adjustment:
T204
1. Receive the PAL Colour Bar signal. If this signal
isnot available, any signalabove the E-5CHband
is acceptable.
»Field strength : 55-80 dBµV
Make sure the frequency is almost the same as
that of the received channel (±30 kHz).
2. Using the channel setting control, make a fre-
quency of 224.25 MHz appear on the screen (the
AFT turns off). If any other channel than Colour
Barisreceived, make itsfrequency on thescreen.
(The AFT turns off when the on-screen display
turns yellow.)
3. Turn T204 clockwise to have a 6V point, and
counterclockwise to have a 0.2V point. Position
the coil at the center of these two points.
4. Adjust T204 so that the DC voltage at pin (1) (AFT
OUT terminal) of IC201 be 3.3 ±0.1 V. (See Fig. 3 )
2
RF AGC
cut-in
adjustment:
R216
1. Receive the PAL Colour Bar signal.
»Field strength : 57 ±1 dBµV (75 ohms open)
2. Connect the oscilloscope to TP210, as shown in
Fig. 4 .
3. Turn R216 to have the highest voltage.
4. Turn R216 slowly in the opposite direction until the
voltage goes down 0.1 V below the highest level.
5. Adjust the signal level to 63-67 dBµV and make
sure there is no noise.
6. Nowadjustthe signallevelto90-95 dBµVandmake
sure there is no chrominance modulation beat.
3
6V
3.3V
DOWN A B' B B" C UP
DC voltage at TP201
Fig. 3
»Bias box: About 4.5 V
Oscilloscope
0.1V
TV Set
Bias box
TP210+
+
–
–
Fig. 4
PIF CHECKING
No. Adjusting point Adjusting procedure/conditions Waveform and others
Tuner IFT
(preset):
TU201
1. Get the tuner ready to receive the E-9CH signal.
but with no signal input. Adjust the PLL data.
2. Connect the sweep generator’s output cable to
the tuner antenna. (RF sweep)
3. Adjust the sweep generator’s output level to 80
dBµV.
4. Connectthe response lead(use a low-impedance
probe with wave detector; see
Fig. 1 ) to the tun-
er’s IF output terminal.
(This terminal must have the probe alone con-
nected.)
5. Set the RF AGC voltage to 0-6 V with no contact
with the waveform.
6. Adjust the tuner IF coil to obtain the waveform as
shown in Fig. 2 .
Note: Be sure to keep the tuner cover in posi-
tion during this adjustment.
1
IF-OUT
1000p 10kΩ
75Ω1000p 100kΩ
Oscilloscope
Fig. 1
E-9CH
PC
– 1.5dB ±0.8dB
Fig. 2
SERVICE ADJUSTMENT
115V ADJUSTMENT
No. Adjusting point Adjusting procedure/conditions Waveform and others
115V
adjustment:
R711
1. Receive the Monoscope Pattern signal.
2. Set to the P-NORM mode.
3. Connect a DC milliammeter between TP602(–)
and TP603(+).
4. Take the beam ammeter reading to make sure
that the beam current is between 900 µA and
1100 µA.
* If not, readjust the FBT screen control to ob-
tain the beam current of 900-1100 µA.
5. Connect a digital voltmeter to TP701.
6. Adjust R711 so that the digital voltmeter should
read 115 ±0.5 V.
1

7
7-1 7-2
20CT-250
CONVERGENCE ADJUSTMENT
No. Adjusting point Adjusting procedure/conditions Waveform and others
Convergence
adjustment
(to be done
after the purity
adjustment)
1. Receive the Crosshatch Pattern signal.
2. Usingthe remote controller,call the Normalmode.
STATIC CONVERGENCE
1. Turn the 4-pole magnet to a proper opening an-
gle in order to superimpose the blue and red col-
ours.
2. Turn the 6-pole magnet to a proper opening an-
glein order tosuperimpose thegreen colourover
the blue and red colours.
DYNAMIC CONVERGENCE
1. Adjust the convergence on the fringes of the
screen in the following steps.
a)
Fig. 6-1 : Drive the wedge at point “a” and
swing the deflection coil upward.
b) Fig. 6-2 : Drive the wedges at points “b” and
“c”and swing the deflection coildownward.
c) Fig. 6-3 : Drive the “c” wedge deeper and
swing the deflection coil rightward.
d) Fig. 6-4 : Drive the “b” wedge deeper and
swing the deflection coil leftward.
2. Fix all the wedges on the cathode ray tube and
apply glass tape over them.
3. Apply lacquer to the deflection yoke lock screw,
magnet unit (purity, 4-pole and 6-pole magnets),
and magnet unit lock screw.
Finally receive the red-only and blue-only signals
and make sure there is no other colour mixed on
the screen.
1
RGB
BGR
R
G
B
R
G
B
B
G
R
B
G
R
RGB
BGR
Fig. 6-2
Fig. 6-1
Fig. 6-3
Fig. 6-4
Fig. 6-5
Fig. 6-6
Lacquer
Wedge "a"
Wedge
"b" Wedge
"c"
About
100°
About
100°
4-pole magnet
6-pole magnet
CRT neck
Lacquer
Purity magnet
PURITY ADJUSTMENT
No. Adjusting point Adjusting procedure/conditions Waveform and others
Purity
adjustment 1. Using the remote controller, make the screen colour green-only.Adjustthecontrastcontroltohaveabeam
current of about 700 µA.
2. Degauss the cathode ray tube enough with the
degaussing coil.
3. Keep the purity magnet in the zero magnetic field
in advance. Roughly adjust the convergence.
4. Observe the points “a” and “b”, as shown in
Fig.
5-1 , through a microscope. Adjust the landing to
the rank “A” requirements.
5. Adjust the raster rotation to “0” eastward.
6. Tighten up the deflection coil screws.
»Tightening torque: 108 ±20 N (11 ±2 kgf)
7. While observing the cathode ray tube corners.
apply the magnet sheet to have the landing at
rank “A”.
Note:Before starting this adjustment, warm
up the unit for 30 minutes or longer at
a beam current of over 700 µA.
Note: Set the service switch S1001 to call the
service mode and press the single-col-
our key on the process remote control-
ler to get the green-only screen.
* Each time the single-colour key is pressed, the
screen colour changes as follows.
1
* Whether in the service mode or
not, hold down the single-colour
key for 1 second or longer and
the service mode is called.
TheTEXTkey or the R.G.Cykey
may be used instead to provide
the single-colour screens.
ab
A
B
A
B
A = B
A = B
Rank "A" (on the
right of the CRT)
Rank "A" (on the
left of the CRT)
Fig. 5-1
Fig. 5-2
Fig. 5-3
Green-only
screen Blue-only
screen Red-only
screen
Single-colour
screen cleared

8
8-1 8-2
20CT-250
No. Adjusting point Adjusting procedure/conditions Waveform and others
Maximum
beam current
(check item)
1. Receive the Monoscope Pattern signal.
2. Set to the P-NORM mode.
3. Connect the DC ammeter between TP602 and
TP603.
»Ammeter’s full-scale : 3 mA range
»Ammeter’s positive (+) lead : TP603
»Ammeter’s negative (-) lead : TP602
4. Make sure the beam current is 1,100 ±100 µA.
Note:Before starting this adjustment, warm
up the unit for 30 minutes or longer at
a beam current of over 700 µA.
3
HORIZONTAL AND VERTICAL CIRCUIT ADJUSTMENT
No. Adjusting point Adjusting procedure/conditions Waveform and others
V-AMP 50
V-LINEARITY -
50 Hz
V-S CORREC-
TION - 50 Hz
V-SHIFT 50 (V-
CENTER)
H-SHIFT (50)
(H-CENTER)
1. Adjust the overscan to 9% typical.
1. Adjust to get the best linearity.
1. Adjust the proper condition.
1. Align the screen center with the CRT's geometri-
cal center (E-5).
1. Align the screen center with the CRT's geometri-
cal center (E-5).
Note: For the V-AMP 60, V-LINEARITY 60, V-S
CORRECTION 60, V-SHIFT 60 and H-
SHIFT 60 adjustments, their corrected
data are automatically entered when the
corresponding 50 Hz mode adjustments
are made.
1The selected channels in paren-
theses have the following signals.
(E-2): crosshatch pattern (50 Hz)
signal
(E-5): monoscopepattern (50 Hz)
signal
Focus adjust-
ment 1. Receive the Monoscope Pattern signal. 2. Set to the P-NORM mode.
3. Adjust the focus control so that the screen be in
best focusing.
2
CRT CUT-OFF, SUB-CONTRAST, WHITE BALANCE AND SUB
BRIGHTNES ADJUSTMENT
No. Adjusting point Adjusting procedure/conditions Waveform and others
CRT cut-off
adjustment:
I2C bus control
adjustment
1. Receive the Monoscope Pattern signal.
2. Set to the P-NORM mode.
3. Turn on the service switch and select the "Cut-
off/background" mode.
4. Set the screen control to 0/10 position.
5. Pressthe “9” keyon the remote controllerto reach
the horizontal centering mode.
6. Turn the screen control clockwise until the hori-
zontal raster of the first glimmering colour be-
comes slightly visible.
7. Adjust the cut-off data of the other two colours
until the horizontal raster becomes whitish.
8. Turnoffthescreen control (counterclockwise) until
the horizontal raster disappears.
Note:Before starting this adjustment, warm
up the unit for 30 minutes or longer at
a beam current of over 700 µA.
9. Press the “9” key on the remote controller to call
the NORMAL mode.
1* First of all, make sure that the
R/G/B cut-off data are all initial
values.
Note:
R CUT OFF UP “1” KEY
DOWN “4” KEY
G CUT OFF UP “2” KEY
DOWN “5” KEY
B CUT OFF UP “3” KEY
DOWN “6” KEY
The data can be turned up and
down with the above keys.
1. Receive the Monoscope Pattern signal.
2. Set to the P-NORM mode.
3. Connect the DC miliammeter between TP602 (-)
and TP603 (+).
» Full Scale: 3.0mA range
4. Make sure the beam current be 1,100µA.
5. Adjust the "G-DRIVE" and "B-DRIVE" data to have
a colour temperature of 12,300°K (white).
6. Adjust the contrast and brightness control to have
a beam current of 200µA.
Ifthecolour temperature is notat12,300°K, go back
to step1 above.
7. Receive the Crosshatch Pattern signal.
8. Adjust the "SUB BRI" bus data, so that the block
1st to 3rd inside the window area will
disappear.(black)
2Sub contrast,
white balance,
& sub bright-
ness Service
mode adjust-
ment:
I2C Bus Con-
trol Adjust-
ment
* 12,300°K X: 0.273
Y: 0.276
(with colour temperature meter
CA-100(MINOLTA).)
Note:
G-DRIVE UP “7” KEY
DOWN “-/--” KEY
B-DRIVE UP “8” KEY
DOWN “0” KEY
The data can be turned up and
down with the above keys.
1 2 3 4 5
Make sure all the 1st, 2nd
and3rd blackportions are at
the same black level.

9
9-1 9-2
20CT-250
PROTECTOR PERFORMANCE CHECK
No. Adjusting point Adjusting procedure/conditions Waveform and others
Beam protector 1. Receive the Monoscope Pattern signal.
2. Set the contrast control to maximum.
3. Set the brightness control to maximum.
4. Make a short-circuit between the collector and
emitter of Q851, Q852 or Q853 and make sure
that the protector is activated and the stand-by
mode is called.
1
High-voltage
protector 1. Receive the Monoscope Pattern signal. 2. Connect the bias box to the cathode (R635 side)
of D607.
3. Adjustthe bias boxvoltage to 18V and make sure
that the protector is not activated.
4. Adjustthe bias boxvoltage to 27V and make sure
that the protector is not activated.
2
Other protec-
tors 1. In checking the performance of other protectors — for example, the one against shorting of
smoothing electrolyticcapacitor of +B line—, pay
attentionnot to damageor deteriorate anyrelated
element.
3
A/V INPUT AND OUTPUT CHECK
No. Adjusting point Adjusting procedure/conditions Waveform and others
Video and
audio output
check
1. Receive the Colour Bar (100% white colour bar,
400 Hz, 100% modulation audio) signal.
2. Terminate the video output with a 75 ohm imped-
ance. Make sure the output is as specified
(1.0 Vp-p ±3 dB).
3. Terminate the audio output with a 10k ohm im-
pedance. Make sure the output is as specified
(1.76 Vp-p ±3 dB).
1
Video and
audio input
check
1. Using the TV/AV key on the remote controller,
make sure that the modes change in the order of
TV, AV and TV again and that the video and au-
dio outputs are according to the input and output
terminals for each mode.
2
PAL CHROMA ADJUSTMENT
No. Adjusting point Adjusting procedure/conditions Waveform and others
Sub-colour
adjustment:
I2C bus
adjustment
1. Receive the PAL Colour Bar signal.
2. Set to the P-NORM mode.
3. Connect the oscilloscope to TP852 (RED cath-
ode). (Use a 10 : 1 probe.)
»Range : 2 V/div.
»Sweep time : 20 µsec/div.
4. Using the remote controller, call the sub-colour
adjustment mode. Adjust the sub-colour data so
that the 75% white and red portions of the PAL
colour bar be at the same level. See Fig. 7 .
5. Clear the adjustment mode.
1
NTSC CHROMA ADJUSTMENT
No. Adjusting point Adjusting procedure/conditions Waveform and others
Sub-tint
adjustment:
I2C bus
adjustment
1. Receive the NTSC 3.58 Colour Bar signal in the
A/V mode.
2. Connect the oscilloscope to pin (36) of IC801(B-
Y) .
»Range : 20 mV/div.
»Sweep time : 20 µsec/div.(Use a 10 : 1 probe.)
3. Adjust the sub-tint data to obtain the waveform
as shown in Fig. 8 .
4. Clear the adjustment mode.
1
Cy GB
WY 100%W
Fig. 7
Mg R
WYCy G Mg R B
Fig. 8
A=B=C
(B–Y)
A
B
C

10
10-1 10-2
20CT-250
No. Adjusting point Adjusting procedure/conditions Waveform and others
FUNCTION CHECK (VIDEO AND AUDIO)
No. Adjusting point Adjusting procedure/conditions Waveform and others
Contrast key 1. Receive the E-5CH signal.
2. Select the contrast on the P-MODE screen.
3. Check whether the Contrast is OK or not with Up/
Down keys.
1
COLOUR
SYSTEM key 1. Receive the NTSC 3.58 colour bar (A/V) signal. Using the COLOUR SYSTEM key, select a mode
other than N3.58 and make sure the colour sys-
tem does not work properly.
8
Channel sign
display colour 1. The display colour of all the channel (0-99) signs must be green Under the AFT on mode.
7
Noise mute
check 1. Receive the PAL Colour Bar signal. 2. Turn upthe sound volume to maximumand make
sure the sound is heard normally from the speak-
ers. Then cut off the signal.
3. Make sure the sound muting functions.
4. Finally turn down the sound volume to minimum.
10
Bilingual Key 1. Receive Bilingual sound signal, press the "Bilin-
gual" key. Check whether there is change
SOUND-1 to SOUND-2.
9
Sharpness key 1. Receive the E-5CH signal.
2. Select the sharpness on the P-MODE screen.
3. Check whether the Sharpness is OK or not with
Up/Down keys.
6
PIC-Normal.
key 1. Press the Normal key on the P-MODE screen to make sure all the displayed items are at normal
settings.
See below for the normal settings.
»Contrast : MAX
»Colour : CENTER
»Brightness : CENTER
»Tint : CENTER
»Sharpness : CENTER
5* Thecontrast, colour,brightness,
tint and sharpness settings are
all normal when these items do
not appear on the screen.
Colour key 1. Receive the E-12CH signal.
2. Select the colour on the P-MODE screen.
3. Check whether the Colour is OK or not with Up/
Down keys.
2
Brightness
key 1. Receive the E-5CH signal. 2. Select the brightness on the P-MODE screen.
3. Check whether the Brightness is OK or not with
Up/Down keys.
3
Tint key 1. Receive theNTSC colour barsignal. (A/V In Only)
2. Select the tint on the P-MODE screen.
3. The tint must be changeable toward green with
the UP key and toward red with the DOWN key.
4

11
11-1 11-2
20CT-250
030 PLL data (upper) CH22
031 PLL data (lower)
032 PLL data (upper) CH23
033 PLL data (lower)
034 PLL data (upper) CH24
035 PLL data (lower)
036 PLL data (upper) CH25
037 PLL data (lower)
038 PLL data (upper) CH26
039 PLL data (lower)
03A PLL data (upper) CH27
03B PLL data (lower)
03C PLL data (upper) CH28
03D PLL data (lower)
03E PLL data (upper) CH29
03F PLL data (lower)
040 PLL data (upper) CH30
041 PLL data (lower)
042 PLL data (upper) CH31
043 PLL data (lower)
044 PLL data (upper) CH32
045 PLL data (lower)
046 PLL data (upper) CH33
047 PLL data (lower)
048 PLL data (upper) CH34
049 PLL data (lower)
04A PLL data (upper) CH35
04B PLL data (lower)
04C PLL data (upper) CH36
04D PLL data (lower)
04E PLL data (upper) CH37
04F PLL data (lower)
050 PLL data (upper) CH38
051 PLL data (lower)
052 PLL data (upper) CH39
053 PLL data (lower)
054 PLL data (upper) CH40
055 PLL data (lower)
056 PLL data (upper) CH41
057 PLL data (lower)
058 PLL data (upper) CH42
059 PLL data (lower)
05A PLL data (upper) CH43
05B PLL data (lower)
05C PLL data (upper) CH44
05D PLL data (lower)
05E PLL data (upper) CH45
05F PLL data (lower)
SUB
ADDRESS
DATA FACTORY
SETTING
REMARKS CRITERIA
76543210
MEMORY MAP (RH-iX3031CEZZ)
SUB
ADDRESS
DATA FACTORY
SETTING
REMARKS CRITERIA
76543210
000 Initialization judgment data “23” Other than $23 $23
001 Initialization judgment data “20” Other than $20 $20
002 Initialization judgment data “13” Other than $13 $13
003 Initialization judgment data “61” Other than $61 $61
004 PLL data (upper) CH0
005 PLL data (lower)
006 PLL data (upper) CH1
007 PLL data (lower)
008 PLL data (upper) CH2
009 PLL data (lower)
00A PLL data (upper) CH3
00B PLL data (lower)
00C PLL data (upper) CH4
00D PLL data (lower)
00E PLL data (upper) CH5
00F PLL data (lower)
010 PLL data (upper) CH6
011 PLL data (lower)
012 PLL data (upper) CH7
013 PLL data (lower)
014 PLL data (upper) CH8
015 PLL data (lower)
016 PLL data (upper) CH9
017 PLL data (lower)
018 PLL data (upper) CH10
019 PLL data (lower)
01A PLL data (upper) CH11
01B PLL data (lower)
01C PLL data (upper) CH12
01D PLL data (lower)
01E PLL data (upper) CH13
01F PLL data (lower)
020 PLL data (upper) CH14
021 PLL data (lower)
022 PLL data (upper) CH15
023 PLL data (lower)
024 PLL data (upper) CH16
025 PLL data (lower)
026 PLL data (upper) CH17
027 PLL data (lower)
028 PLL data (upper) CH18
029 PLL data (lower)
02A PLL data (upper) CH19
02B PLL data (lower)
02C PLL data (upper) CH20
02D PLL data (lower)
02E PLL data (upper) CH21
02F PLL data (lower)

12
12-1 12-2
20CT-250
090 PLL data (upper) CH70
091 PLL data (lower)
092 PLL data (upper) CH71
093 PLL data (lower)
094 PLL data (upper) CH72
095 PLL data (lower)
096 PLL data (upper) CH73
097 PLL data (lower)
098 PLL data (upper) CH74
099 PLL data (lower)
09A PLL data (upper) CH75
09B PLL data (lower)
09C PLL data (upper) CH76
09D PLL data (lower)
09E PLL data (upper) CH77
09F PLL data (lower)
0A0 PLL data (upper) CH78
0A1 PLL data (lower)
0A2 PLL data (upper) CH79
0A3 PLL data (lower)
0A4 PLL data (upper) CH80
0A5 PLL data (lower)
0A6 PLL data (upper) CH81
0A7 PLL data (lower)
0A8 PLL data (upper) CH82
0A9 PLL data (lower)
0AA PLL data (upper) CH83
0AB PLL data (lower)
0AC PLL data (upper) CH84
0AD PLL data (lower)
0AE PLL data (upper) CH85
0AF PLL data (lower)
0B0 PLL data (upper) CH86
0B1 PLL data (lower)
0B2 PLL data (upper) CH87
0B3 PLL data (lower)
0B4 PLL data (upper) CH88
0B5 PLL data (lower)
0B6 PLL data (upper) CH89
0B7 PLL data (lower)
0B8 PLL data (upper) CH90
0B9 PLL data (lower)
0BA PLL data (upper) CH91
0BB PLL data (lower)
0BC PLL data (upper) CH92
0BD PLL data (lower)
0BE PLL data (upper) CH93
0BF PLL data (lower)
SUB
ADDRESS
DATA FACTORY
SETTING
REMARKS CRITERIA
76543210
060 PLL data (upper) CH46
061 PLL data (lower)
062 PLL data (upper) CH47
063 PLL data (lower)
064 PLL data (upper) CH48
065 PLL data (lower)
066 PLL data (upper) CH49
067 PLL data (lower)
068 PLL data (upper) CH50
069 PLL data (lower)
06A PLL data (upper) CH51
06B PLL data (lower)
06C PLL data (upper) CH52
06D PLL data (lower)
06E PLL data (upper) CH53
06F PLL data (lower)
070 PLL data (upper) CH54
071 PLL data (lower)
072 PLL data (upper) CH55
073 PLL data (lower)
074 PLL data (upper) CH56
075 PLL data (lower)
076 PLL data (upper) CH57
077 PLL data (lower)
078 PLL data (upper) CH58
079 PLL data (lower)
07A PLL data (upper) CH59
07B PLL data (lower)
07C PLL data (upper) CH60
07D PLL data (lower)
07E PLL data (upper) CH61
07F PLL data (lower)
080 PLL data (upper) CH62
081 PLL data (lower)
082 PLL data (upper) CH63
083 PLL data (lower)
084 PLL data (upper) CH64
085 PLL data (lower)
086 PLL data (upper) CH65
087 PLL data (lower)
088 PLL data (upper) CH66
089 PLL data (lower)
08A PLL data (upper) CH67
08B PLL data (lower)
08C PLL data (upper) CH68
08D PLL data (lower)
08E PLL data (upper) CH69
08F PLL data (lower)
SUB
ADDRESS
DATA FACTORY
SETTING
REMARKS CRITERIA
76543210

13
13-1 13-2
20CT-250
0F0 CH7 CH5 CH5 CH4 CH3 CH2 CH1 CH0 SKIP SKIP ON 00
0F1 CH15 CH5 CH5 CH4 CH3 CH2 CH1 CH0 0 : OFF
0F2 CH23 CH22 CH21 CH20 CH19 CH18 CH17 CH16 1 : ON
0F3 CH31 CH30 CH29 CH28 CH27 CH26 CH25 CH24
0F4 CH39 CH38 CH37 CH36 CH35 CH34 CH33 CH32
0F5 CH47 CH46 CH45 CH44 CH43 CH42 CH41 CH40
0F6 CH55 CH54 CH53 CH52 CH51 CH50 CH49 CH48
0F7 CH63 CH62 CH61 CH60 CH59 CH58 CH57 CH56
0F8 CH71 CH70 CH69 CH68 CH67 CH66 CH65 CH64
0F9 CH79 CH78 CH77 CH76 CH75 CH74 CH73 CH72
0FA CH87 CH86 CH85 CH84 CH83 CH82 CH81 CH80
0FB CH95 CH94 CH93 CH92 CH91 CH90 CH89 CH88
0FC CH99 CH98 CH97 CH96
0FD
0FE
0FF
SUB
ADDRESS
DATA FACTORY
SETTING
REMARKS CRITERIA
76543210
0C0 PLL data (upper) CH94
0C1 PLL data (lower)
0C2 PLL data (upper) CH95
0C3 PLL data (lower)
0C4 PLL data (upper) CH96
0C5 PLL data (lower)
0C6 PLL data (upper) CH97
0C7 PLL data (lower)
0C8 PLL data (upper) CH98
0C9 PLL data (lower)
0CA PLL data (upper) CH99
0CB PLL data (lower)
0CC POWER TV/AV 80
0CD BLUE BACKGROUND O ne-digit/two-digit OFF/ . Factory-set at ON AA
0CE LANGUAGE 01
0CF LAST POSITION 01
0D0 LAST CONTRAST 3F
0D1 LAST COLOUR 1F
0D2 LAST BRIGHTNESS 1F
0D3 LAST TINT 1F
0D4 LAST SHARPNESS 1F
0D5 LASTVOLUME 00
0D6 LAST SERVICE MODE 00
0D7
0D8
0D9
0DA
0DB
0DC
0DD
0DE
0DF
0E0 CH7 CH5 CH5 CH4 CH3 CH2 CH1 CH0 AFT AFT OFF FF
0E1 CH15 CH14 CH13 CH12 CH11 CH10 CH9 CH8 0 : OFF
0E2 CH23 CH22 CH21 CH20 CH19 CH18 CH17 CH16 1 : ON
0E3 CH31 CH30 CH29 CH28 CH27 CH26 CH25 CH24
0E4 CH39 CH38 CH37 CH36 CH35 CH34 CH33 CH32
0E5 CH47 CH46 CH45 CH44 CH43 CH42 CH41 CH40
0E6 CH55 CH54 CH53 CH52 CH51 CH50 CH49 CH48
0E7 CH63 CH62 CH61 CH60 CH59 CH58 CH57 CH56
0E8 CH71 CH70 CH69 CH68 CH67 CH66 CH65 CH64
0E9 CH79 CH78 CH77 CH76 CH75 CH74 CH73 CH72
0EA CH87 CH86 CH85 CH84 CH83 CH82 CH81 CH80
0EB CH95 CH94 CH93 CH92 CH91 CH90 CH89 CH88
0EC CH99 CH98 CH97 CH96
0ED
0EE
0EF
SUB
ADDRESS
DATA FACTORY
SETTING
REMARKS CRITERIA
76543210

14
14-1 14-2
20CT-250
SUB
ADDRESS
FACTORY
SETTING
REMARKS CRITERIA
76543210
190 P/N KIL NOISE DET 000
191 RGB CONTRAST 255 FF
192 Y γWPL SW 0,0 00
193 AFC MODE 102
194 B.S OFF P/N GP CL-L SW 0,0,1 00
195 CLL LEVEL PN CD ATT 2,2 A0
196 BLACK STRETCH OFFSET DC TRAN RATE APA-CON F0 7,2,2 EA
197 ABL POINT ABL GAIN 0,1 04
198 COINCIDENT 0 01*
199 NOISE DET LEVEL 000
19A N COMB 180
19B S-FIELD SCD ATT DEMP F0 S GP V-ID SW S KIL BELL F0 21
19C
19D
19E
19F
1A0 TOF Q (AV) TOF F0 (AV) TOF Q (TV) TOF F0 (TV) PAL 8B
1A1 TOF Q (AV) TOF F0 (AV) TOF Q (TV) TOF F0 (TV) SECAM 8B
1A2 TOF Q (AV) TOF F0 (AV) TOF Q (TV) TOF F0 (TV) N443 8B
1A3 TOF Q (AV) TOF F0 (AV) TOF Q (TV) TOF F0 (TV) N358 8B
1A4 C-TRAP Q (AV) C-TRAP F0 (AV) C-TRAP Q (TV) C-TRAP F0 (TV) PAL 66
1A5 C-TRAP Q (AV) C-TRAP F0 (AV) C-TRAP Q (TV) C-TRAP F0 (TV) SECAM 66
1A6 C-TRAP Q (AV) C-TRAP F0 (AV) C-TRAP Q (TV) C-TRAP F0 (TV) N443 66
1A7 C-TRAP Q (AV) C-TRAP F0 (AV) C-TRAP Q (TV) C-TRAP F0 (TV) N358 66
1A8 N358 SHARPNESS 10 0A
1A9 N358 TR ON 00
1AA FAVORITE CH (RED) 10CH 0A
1AB FAVORITE CH (GREEN) 20CH 14
1AC FAVORITE CH (YELLOW) 30CH 1E
1AD FAVORITE CH (CYAN) 40CH 28
1AE
1AF
1B0
1B1
1B2
1B3
1B4
1B5
1B6
1B7
1B8
1B9
1BA
1BB
1BC
1BD
1BE
1BF
DATA
SUB
ADDRESS
FACTORY
SETTING
REMARKS CRITERIA
DATA
164 AUDIO SYSTEM (1) VIDEO SYSTEM (2) AUTO 00
165
166
167
168
169
16A
16B
16C
16D
16E
16F
170 CUT OFF (R) 0 00
171 CUT OFF (G) 0 00
172 CUT OFF (B) 0 00
173 DRIVE (G) 127 7F
174 DRIVE (R) 127 7F
175 TV H-CENTER (50Hz) 7 07
176 TV H-CENTER (60Hz) 12 0C
177 H BLK PHASE V-CENTER 50 0,5 05
178 V-AMPLITUDE 50 58 74
179 V S-CORRECTION 50 67 86
17A V-LINEALITY 50 16 80
17B Y SUB CONTRAST 18 12
17C SUB COLOUR 110 6E
17D SUB BRIGHT 127 7F
17E SUB TINT 70 46
17F SUB SHARPNESS 28 1C
180 DELAY PAL (AV) DELAY PAL (TV) 2,2 22
181 DELAY SECAM (AV) DELAY SECAM (TV) 4,4 44
182 DELAY NTSC (AV) DELAY NTSC (TV) 2,2 22
183 DELAY B/W (AV) DELAY B/W (TV) 2,2 22
184 R-Y BLACK OFFSET B-Y BLACK OFFSET 10,6 A6
185 Y-MUTE AV2 OFF/ON 04
186 V-CENTER 60 2 02
187 V-AMPLITUDE 60 59 76
188 V S-CORRECTION 60 74 E8
189 V-LINEARITY 60 14 70
18A WIDE V-BLK START PHASE 50 58 3A
18B WIDE V-BLK START PHASE 60 60 3C
18C WIDE V-BLK STOP PHASE 50 25 19
18D WIDE V-BLK STOP PHASE 60 20 14
18E SUB CONTRAST 255 FF
18F
76543210

15
15-1 15-2
20CT-250
TROUBLE SHOOTING TABLE
NO RASTER
Blown out.
Replace the fuse.
Check Q701 and IC751.
Abnormal
YES
YES
NO
ON/OFF ON
NO
Abnormal
The fuse is again blown out.
Horizontal circuit oscillate ?
Check Q1005, Q1006,
IC603 and IC801.
D1013 (Power LED Red)
turns on or turns ON/OFF.
Check T701 pin (1) voltage
(Approx. 310V at 220V AC)
Check C707, D701, D702,
D703 and D704.
Check F701.
Normal
Normal
Check Secondary Main+B
(Approx. 115V)
Normal
Normal Abnormal
Normal
Check CRT connector K1-
K5 bias.
Check
C866 and
L851.
Check
IC801 Bus error
mode.
See
Fig. 1
or Check
IC602.
Checking the
protector circuit
(The protector
circuit still works
even if there is no
vertical waveform
at pin (2) of IC1001.)
Check R609 and R611.
D1013 (Power LED Green)
turns on.
Check D708 and D732.
Check R702 and D709.
Normal
If a bus error happens, the LED RED (pin 3) indicator starts flashing and the power
is turned off. The power key is still effective.
IC1003
EEPROM (ST24C04)
IC801
V/C/J (TB1226DN)
TU201
PLL (N0004KJ)
2s 0.5s
Fig. 1
TROUBLE SHOOTING TABLE (Continued)
NO PICTURE, NO SOUND
YES
YES
YES
(Signal)
NO
YES
(Noise)
NO
NO
Does noise or signal appear
at pin (13) of IC201 ?
NO SOUND
No snow noise.
Does noise or signal appear at pin (21)
of IC201 ?
Noise increases but no signal is
received.
Check the tuner supply voltage MB
must be approx, 9V. BP must approx.
5V. BT must be approx, 31V. And CH
preset data check.
Check the tuner AGC.
Normal
Normal Abnormal
Does noise or
signal appear at
pin (1) of IC801 ?
Check PIF circuits
and its related
parts.
Check IC801. Check A/V sw
circuits (IC401).
Check IC201.
Check the tuner
circuit.
Does the noise level increase at max.
Contrast, Brightness and Sound controls ?
CIRCUITS TO BE CHECKED:
»Tuner.
»PIF.
»Automatic Gain Control.
»(5V), (9V) Power Source.
CIRCUITS TO BE CHECKED:
»SIF Amplifier Circuit.
»Sound Detector Circuit.
»Sound Switch and Att. Control.
»Audio Output Circuit.
YES
NO
YES
NO
Does signal appear at pin
(1) and (8) of IC302 ?
Does signal appear at pin
(3) of IC351 ?
Check pin (5) of IC351 and
peripheral circuit.
Check IC201 and peripheral
circuit.
Check pin (14), (15) of
IC201.
Check Q207 and peripheral
circuit.
Check IC302 and peripheral
circuit.

16
16-1 16-2
20CT-250
TROUBLE SHOOTING TABLE (Continued)
NO SPECIFIC COLOUR
Is some colour produced in
B/W broadcast reception ?
Is the white balance properly
adjusted ?
Readjust the white balance.
The picture colour is yellow.The picture colour is magenta.The picture colour is cyan.
Check Q851 and its
adjacent circuits. Check Q852 and its adjacent circuits. Check Q853 and its adjacent circuits.
Check IC801 and bias
control circuit.
Normal Normal
“SECAM”“PAL”/“NTSC”
NO SPECIFIC COLOUR
“PAL”/“NTSC”/“SECAM”
(NO COLOUR SYNCHRONIZATION)
NO YES
YES
NO
Check IC801, R809, R810,
R811, D801, D802, D803,
Q801, Q802, Q803,Q804
and Q805.
Check X801, C810, C815,
C816 and R814. Check C901 and pin (31) of IC1001.
TROUBLE SHOOTING TABLE (Continued)
NEITHER VERTICAL NOR
HORIZONTAL SYNCHRONIZATION
CIRCUIT TO BE CHECKED:
»Sync. Separator Circuit.
NO VERTICAL SCAN
Vertical linearity is abnormal.
Check C515, C519, R511,
R513 and R514.
Vertical size is abnormal.
Check R510, C513, C514
and C501.
Check IC801 and Q401.
DEFECTIVE VERTICAL AMP.
AND VERTICAL LINEARITY
Readjust vertical size.
(Bas Data)
Check IC501.Check C506.
Check IC501 bias.
Normal Abnormal

20CT-250
17
CHASSIS LAYOUT
21CT-25
as is
654321
A
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20CT-250
18
TOP VIEW
SIDE VIEW
SOLID STATE DEVICE BASE DIAGRAM
56 29
128
TB1226
ST24C04
42 22
121
iX3031
85
14
iX1779CE
16 9
18
BA7357S
22 12
111
2SA1015
2SC1815
2SC1906 2SC2482 KiA7045P
TA78L09 UPC78L05 iX0037CE 2SC3789 TA7348P
BASE
COLLECTOR
EMITTER
CATHODE
ANODE
BASE
COLLECTOR
EMITTER
BCE BCE
KA7809
KA7805
123
ANODE
(RED)
CATHODE
(COMMON)
ANODE
(GREEN)
123 3 2 1 ECB
TDA7056AiX0640CE
PX0003PE2SD18842SD2586
1917
19

20CT-250 20CT-250
121110987654321
A
B
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19 20
DESCRIPTION OF SCHEMATIC DIAGRAM
SAFETY NOTES:
1. DISCONNECT THEAC PLUG FROM THE AC OUTLET BEFORE
REPLACINGPARTS.
2. SEMICONDUCTOR HEAT SINKS SHOULD BE REGARDED AS
POTENTIALSHOCK HAZARDS WHEN THE CHASSIS ISOPER-
ATING.
IMPORTANT SAFETY NOTICE:
PARTS MARKED WITH " å " ( ) ARE IMPORTANT FOR
MAINTAINING THE SAFETYOFTHE SET. BE SURE TOREPLACE
THESE PARTS WITH SPECIFIED ONES FOR MAINTAINING THE
SAFETY AND PERFORMANCE OF THE SET.
SERVICE PRECAUTION:
THEAREA ENCLOSED BYTHIS LINE ( ) IS DIRECTLY
CONNECTED WITHAC MAINS VOLTAGE.
WHENSERVICINGTHEAREA, CONNECTAN ISOLATING TRANS-
FORMER BETWEEN TV RECEIVER AND AC LINE TO ELIMINATE
HAZARD OF ELECTRIC SHOCK.
NOTES:
1. The unit of resistance "ohm" is omitted.
(K = 1000 ohms, M = Meg ohm).
2. All resistors are 1/8 watt, unless otherwise noted.
3. All capacitors are µ F, unless otherwise noted. (P = µµ F).
4. All capacitors are 50V, unless otherwise noted.
VOLTAGE MEASUREMENT CONDITIONS:
1. Voltage in parenthesis measured with no Signal.
2. Voltages without parenthesis measured with 3mV B & W or
Colour-Signal.
3. All the voltages in each point are measured with VTVM.
WAVEFORM MEASUREMENT CONDITIONS:
1. Colour bar generator signal of 1.5V peak to peak applied at
Base of Video BufferAmp. Q202.
2. Approximately 4.0 V AGC bias.
1 2.0 Vp-p (H) 2 1.3 Vp-p (H) 3 1.5 Vp-p (H) 4 3.0 Vp-p (H) 5 3.0 Vp-p (H)
6 3.0 Vp-p (H) 7 80 Vp-p (H) 8 80 Vp-p (H) 9 80 Vp-p (H) 10 5.7 Vp-p (H)
11 1.8 Vp-p (V) 12 0.8 Vp-p (H) 13 9.2 Vp-p (H) 14 1.8 Vp-p (V) 15 55 Vp-p (V)
16 145 Vp-p (H) 17 1000 Vp-p (H) 18 150 Vp-p (H) 19 520 Vp-p (H)
WAVEFORMS
ËË
ËË
ËTuner
NOTE: The parts here shown are supplied as an assembly but not independently. åå
åå
åRTUNQ0004KJZZ
ËË
ËË
ËInfrared Remote Control Unit
NOTE: The parts here shown are supplied as an assembly but not independently. RRMCG0018PESA
654321
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G
H

20CT-250 20CT-250
121110987654321
A
B
C
D
E
F
G
H
21 22
SCHEMATIC DIAGRAM