Sharp 20CT-250 Schematic

20CT-250

SERVICE MANUAL

S88U521CT-250

COLOUR TELEVISION

Chassis No. G2

MODEL

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.

20CT-250

FEATURE

User Preset Timer (On Timer/Sleep Timer/Reminder)

2 Selectable OSD Languages (English/Thai)

CATV (Hyper Band) Ready 〈Used Frequency Synthesizer Tuner〉

NTSC 4.43/3.58MHz (AV only), Rear AV IN/OUT terminal

Blue Back Noise Mute

Fine Tuning Adjustable with Remote Control

Full Auto Channel Preset And Auto Channel Skip

100 CH Program Memory

Aperture Control Circuit

Black Stretch Circuit

Bilingual System (Mono)

Auto Channel Scan System

Favorite Channel Memory System

CONTENTS

Page

» SPECIFICATIONS...............................................2

» IMPORT ANT SER VICE NOTES ......................... 2

» ADJUSTMENT PRECAUTIONS ........................ 3

» SERVICE ADJUSTMENT................................... 6

» TROUBLE SHOOTING T ABLE......................... 15

» SOLID ST ATE DEVICE BASE DIAGRAM ........ 18

» CHASSIS LAYOUT............................................17

» SCHEMA TIC DIAGRAM ................................... 19

» BLOCK DIAGRAM ............................................23

» PRINTED WIRING BOARD ASSEMBLIES...... 25

» REPLACEMENT P AR TS LIST.......................... 27

Page

WARNING

The chassis in this receiver is partially hot. Use an isolation transformer between the line cord plug and power receptacle, when servicing this chassis. To prevent electric shock, do not remove cover. No user – serviceable parts inside. Refer servicing to qualified service personnel.

SHARP CORPORATION

20CT-250

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

Power Input........................................................................ 220-240V AC 50/60 Hz

Power Consumption ........................................................................................ 80W

Audio Power Output Rating ........................................................................... 3.0 W

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

Weight (approx.): 20.2 kg

Cabinet Material.................................................................................... All Plastics

(at Max.)

Height: 462.5 mm

Depth: 481.0 mm

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

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

2. To keep the set in a normal operation, be sure to make it function on 22.0 kV ±1.5 kV (at

3. Do not substitute a picture tube with unauthorized types and/or brands which may cause

IMPORT ANT SERVICE NOTES

the high voltage completely

kV (at beam 0 µA) for the set. 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.

excess X-ray radiation.

Specifications are subject to change without prior notice.

2-1 2-2

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 resistorcapacity networks, mechanical insulators etc.

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 I

C bus control includes preset-only items and variable data.

1. Calling the service mode by the microprocessor

1 Set the switch S1006 to the service mode position, and the microprocessor is put in the service mode (adjustment through the I

2 Press the CH UP/DOWN keys on the remote controller to select the modes one by one. 3 Press the CH UP/DOWN keys on the remote controller to select the modes in the order opposite to the

above step 2. 4 Using the VOLUME UP/DOWN keys on the remote controller, the data can be modified. 5 Set the switch S1006 to the normal mode (OFF) position, and the microprocessor is put out of the

service mode.

C bus control).

2. Factory presettings

1 Set the switch S1006 to the service mode position and turn on the main power switch. Initial values are

automatically preset only when a new E

2 The initial data are preset as listed on page 5. 3 Keep 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.-1 above). 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

PROM is used (judgment with the first 4 bytes).

reference.

3-1 3-2

20CT-250

SERVICE MODE

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.

(1) Press the specific keys to change the modes as follows.

20CT-250

RASTER mode

Y-DY/OP ADJUST mode 60 Hz ADJUST mode SUB-ADJUST mode

R-CUT OFF G-CUT OFF B-CUT OFF

50 Hz ADJUST mode COLOUR ADJUST 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)

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.

CUT-OFF mode

KEY R-CUT OFF

G-CUT OFF B-CUT OFF R-DRIVE B-DRIVE LATERAL mode

50 Hz ADJUST mode COLOUR ADJUST mode

CUT-OFF/BKGD mode

CUT-OFF/ BKGD mode

LATERAL mode

UP 1 KEY

2 KEY 3 KEY 7 KEY 8 KEY

4-1 4-2

In the direction of arrow : CH DOWN key In the opposite direction : CH UP key

R-DRIVE

3-sec time out3-sec time out

DOWN 4 KEY

5 KEY 6 KEY F/B KEY 0 KEY

9 KEY

SECAM R-Y (R-Y)

SECAM B-Y (B-Y)

In the direction of arrow : CH DOWN key In the opposite direction : CH UP key

B-DRIVE

* 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.

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

* The following keys are used to go directly to their respective modes.

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 TIMED PAGE SUB BRIGHT SIZE SUB TINT HOLD SUB SHARP RESET R-Y YELLOW B-Y CYAN A/V 1/2 SKIP VIDEO MUTE BLUE BACK

*To go to the service mode, the data at the E

given below, the E2PROM is initialized according to the table below.

Address: Data

00H : 23H 02H : 13H 01H : 20H 03H : 61H

(00H) –––––––––– 23H (01H) –––––––––– 20H (02H) –––––––––– 13H (03H) –––––––––– 61H R CUT OFF 0 G CUT OFF 0 B CUT OFF 0 G DRIVE 0 B DRIVE 0 50Hz V-AMP 0 50Hz V-LINEARITY 0 50Hz S-CORRECTION 0 50Hz V-PHASE 0 50Hz H-PHASE 0 V-BLK ST 50 0 V-BLK SP 50 0 60Hz V-AMP 0 60Hz V-LINEARITY 0 60Hz S-CORRECTION 0

60Hz V-PHASE 0 60Hz H-PHASE 0 60Hz V BLK ST 0 60Hz V BLK SP 0 SECAM R-Y 0 SECAM B-Y 0 SUB-CONTRAST 0 SUB-BRIGHT 0 SUB-COLOUR 0 SUB-TINT 0 SUB-SHARPNESS 0 Y SUB-CONTRAST 0 DT P AL TV/AV 0 DT SECAM TV/AV 0 DT NTSC TV/A V 0 DT B/W TV/AV 0 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-

*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.

E2PROM item Data adjustable range Data initial value Remarks

wise the E

PROM will be initialized when the AC power is turned on.

PROM’s addresses 00H thru 03H are read. If the data are not as

255 0

255 127

127 58

31 16

127 67 *1

~ ~

31 7 +5 *1

63 58→63 (50Hz)

127 25

127 59

31 14

127 74 *2

~ ~

31 12

63 60→63 (60Hz)

127 20

15 10

15 6

255 255 *2

255 127

255 110

127 70

63 28

31 18 *2

~ ~ ~ ~ ~

75–3*1

72 *4

7 2/2 *2 7 4/4 *2 7 2/2 *2 7 2/2 *2

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.)

POS RECEPTION FREQ (MHZ)

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

S-SYSTEM

POS RECEPTION FREQ (MHZ)

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

S-SYSTEM

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

20CT-250

5-1 5-2

» Bias box: About 4.5 V

Oscilloscope

0.1V

TV Set

Bias box

TP210+

–

Fig. 4

SERVICE ADJUSTMENT

115V ADJUSTMENT

No. Adjusting point Adjusting procedure/conditions W aveform and others

115V

adjustment: R711

No. Adjusting point Adjusting procedure/conditions W aveform and others

Tuner IFT (preset): TU201

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.

PIF CHECKING

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. Connect the response lead (use a low-impedance probe with wave detector; see er’s IF output terminal. (This terminal must have the probe alone connected.)

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.

Fig. 1

) to the tun-

IF-OUT

1000p

75Ω

1000p

E-9CH

10kΩ

100kΩ

Oscilloscope

Fig. 1

– 1.5dB ± 0.8dB

Fig. 2

PIF/AFT/AGC ADJUSTMENT

No. Adjusting point Adjusting procedure/conditions W aveform and others

VCO adjust-

1 * Warm up the unit for longer than

ment: T203

AFT

adjustment: T204

RF AGC

cut-in adjustment: R216

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 voltage 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. Receive the PAL Colour Bar signal. If this signal is not available, any signal above the E-5CH band 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 frequency of 224.25 MHz appear on the screen (the AFT turns off). If any other channel than Colour Bar is received, make its frequency on the screen. (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

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. Now adjust the signal level to 90-95 dBµV and make sure there is no chrominance modulation beat.

Fig. 3

)

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.

DC voltage at TP201

3.3V

DOWN

A B' B B" C

Fig. 3

20CT-250

6-1 6-2

PURITY ADJUSTMENT

No. Adjusting point Adjusting procedure/conditions W aveform and others

Purity adjustment

1. Using the remote controller, make the screen colour green-only. Adjust the contrast control to have a beam 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

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-colour key on the process remote controller to get the green-only screen.

* Each time the single-colour key is pressed, the

screen colour changes as follows.

Fig.

Green-only

screen

Blue-only

screen

Single-colour

screen cleared

Red-only

screen

* Whether in the service mode or

not, hold down the single-colour key for 1 second or longer and the service mode is called.

The TEXT key or the R.G.Cy key may be used instead to provide the single-colour screens.

Fig. 5-1

Fig. 5-2

Rank "A" (on the right of the CRT)

Fig. 5-3

Rank "A" (on the

left of the CRT)

A = B

CONVERGENCE ADJUSTMENT

No. Adjusting point Adjusting procedure/conditions W aveform and others

Convergence adjustment (to be done after the purity adjustment)

1. Receive the Crosshatch Pattern signal.

2. Using the remote controller, call the Normal mode.

STATIC CONVERGENCE

1. Turn the 4-pole magnet to a proper opening angle in order to superimpose the blue and red colours.

2. Turn the 6-pole magnet to a proper opening angle in order to superimpose the green colour over the blue and red colours.

DYNAMIC CONVERGENCE

1. Adjust the convergence on the fringes of the screen in the following steps.

Fig. 6-1

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.

: Drive the wedge at point “a” and

swing the deflection coil upward.

Fig. 6-2

: Drive the wedges at points “b” and

“c” and swing the deflection coil downward.

Fig. 6-3

: Drive the “c” wedge deeper and

swing the deflection coil rightward.

Fig. 6-4

: Drive the “b” wedge deeper and

swing the deflection coil leftward.

B G R

R G B

About 100°

Lacquer

Wedge "b"

BGR

Fig. 6-1

RGB

Fig. 6-2

RGB

Fig. 6-3

BGR

Fig. 6-4

Wedge "a"

Fig. 6-5

4-pole magnet

6-pole magnet

CRT neck

B G R

R G B

About 100°

Wedge "c"

7-1 7-2

Purity magnet

Fig. 6-6

Lacquer

20CT-250

CRT CUT-OFF, SUB-CONTRAST, WHITE BALANCE AND SUB BRIGHTNES ADJUSTMENT

No. Adjusting point Adjusting procedure/conditions W aveform and others

1 * First of all, make sure that the

CRT cut-off adjustment:

C bus control

I adjustment

Sub contrast,

white balance, & sub bright-

ness Service mode adjustment:

C 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 "Cutoff/background" mode.

4. Set the screen control to 0/10 position.

5. Press the “9” key on the remote controller to reach the horizontal centering mode.

6. Turn the screen control clockwise until the horizontal raster of the first glimmering colour becomes slightly visible.

7. Adjust the cut-off data of the other two colours until the horizontal raster becomes whitish.

8. Turn off the screen 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. 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. If the colour temperature is not at 12,300°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)

R/G/B cut-off data are all initial values.

Note:

R CUT OFF UP “1” KEY

G CUT OFF UP “2” KEY

B CUT OFF UP “3” KEY

The data can be turned up and down with the above keys.

* 12,300°K X: 0.273

(with colour temperature meter CA-100 (MINOLT A).)

Note:

G-DRIVE UP “7” KEY

B-DRIVE UP “8” KEY

The data can be turned up and down with the above keys.

1 2 3 4 5

Make sure all the 1st, 2nd and 3rd black portions are at the same black level.

DOWN “4” KEY

DOWN “5” KEY

DOWN “6” KEY

Y: 0.276

DOWN “-/--” KEY

DOWN “0” KEY

No. Adjusting point Adjusting procedure/conditions W aveform 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.

HORIZONTAL AND VERTICAL CIRCUIT ADJUSTMENT

No. Adjusting point Adjusting procedure/conditions W aveform and others

V-AMP 50

1 The selected channels in paren-

V-LINEARITY 50 Hz

V-S CORRECTION - 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 geometrical center (E-5).

Note: For the V-AMP 60, V-LINEARITY 60, V -S

CORRECTION 60, V-SHIFT 60 and HSHIFT 60 adjustments, their corrected data are automatically entered when the corresponding 50 Hz mode adjustments are made.

theses have the following signals. (E-2): crosshatch pattern (50 Hz)

signal

(E-5): monoscope pattern (50 Hz)

signal

20CT-250

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.

8-1 8-2

PAL CHROMA ADJUSTMENT

No. Adjusting point Adjusting procedure/conditions W aveform and others

Sub-colour adjustment:

I adjustment

C bus

1. Receive the PAL Colour Bar signal.

2. Set to the P-NORM mode.

3. Connect the oscilloscope to TP852 (RED cathode). (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

5. Clear the adjustment mode.

Fig. 7

Y 100%W

Fig. 7

Mg R

PROTECTOR PERFORMANCE CHECK

No. Adjusting point Adjusting procedure/conditions W aveform and others

Beam protector 1. Receive the Monoscope Pattern signal.

High-voltage

protector

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. Receive the Monoscope Pattern signal.

2. Connect the bias box to the cathode (R635 side) of D607.

3. Adjust the bias box voltage to 18 V and make sure that the protector is not activated.

4. Adjust the bias box voltage to 27 V and make sure that the protector is not activated.

NTSC CHROMA ADJUSTMENT

No. Adjusting point Adjusting procedure/conditions W aveform and others

Sub-tint adjustment:

I adjustment

C bus

1. Receive the NTSC 3.58 Colour Bar signal in the A/V mode.

2. Connect the oscilloscope to pin (36) of IC801(BY) .

» 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

4. Clear the adjustment mode.

Fig. 8

(B–Y) A B C

WYCy G Mg R

Fig. 8

A=B=C

Other protec-

tors

1. In checking the performance of other protectors — for example, the one against shorting of smoothing electrolytic capacitor of +B line —, pay attention not to damage or deteriorate any related element.

A/V INPUT AND OUTPUT CHECK

No. Adjusting point Adjusting procedure/conditions W aveform and others

Video and

audio output check

Video and

audio input check

1. Receive the Colour Bar (100% white colour bar, 400 Hz, 100% modulation audio) signal.

2. T erminate the video output with a 75 ohm impedance. Make sure the output is as specified (1.0 Vp-p ±3 dB).

3. Terminate the audio output with a 10k ohm impedance. Make sure the output is as specified (1.76 Vp-p ±3 dB).

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 audio outputs are according to the input and output terminals for each mode.

20CT-250

9-1 9-2

+ 20 hidden pages