Toshiba 20A42 Schematic

SERVICE MANUAL

DOCUMENT CREATED IN JAPAN, Jun., 2002

COLOR TELEVISION

FILE NO. 050-200209

20A42

SERVICING NOTICES ON CHECKING

As for the places which need special attentions, they are indicated with the labels or seals on the cabinet, chassis and parts. Make sure to keep the indications and notices in the operation manual.

2. AVOID AN ELECTRIC SHOCK

There is a high voltage part inside. Avoid an electric shock while the electric current is flowing.

3. USE THE DESIGNATED PARTS

The parts in this equipment have the specific characters of incombustibility and withstand voltage for safety. Therefore, the part which is replaced should be used the part which has the same character. Especially as to the important parts for safety which is indicated in the circuit diagram or the table of parts as a mark, the designated parts must be used.

4. PUT PARTS AND WIRES IN THE ORIGINAL POSITION AFTER ASSEMBLING OR WIRING

There are parts which use the insulation material such as a tube or tape for safety, or which are assembled in the condition that these do not contact with the printed board. The inside wiring is designed not to get closer to the pyrogenic parts and high voltage parts. Therefore, put these parts in the original positions.

5. TAKE CARE TO DEAL WITH THE CATHODE-RAY TUBE

In the condition that an explosion-proof cathoderay tube is set in this equipment, safety is secured against implosion. However, when removing it or serving from backward, it is dangerous to give a shock. Take enough care to deal with it.

6. AVOID AN X-RAY1. KEEP THE NOTICES

Safety is secured against an X-ray by considering about the cathode-ray tube and the high voltage peripheral circuit, etc. Therefore, when repairing the high voltage peripheral circuit, use the designated parts and make sure not modify the circuit. Repairing except indicates causes rising of high voltage, and it emits an X-ray from the cathoderay tube.

PERFORM A SAFETY CHECK AFTER

7. SERVICING

Confirm that the screws, parts and wiring which were removed in order to service are put in the original positions, or whether there are the portions which are deteriorated around the serviced places serviced or not. Check the insulation between the antenna terminal or external metal and the AC cord plug blades. And be sure the safety of that.

(INSULATION CHECK PROCEDURE)

Unplug the plug from the AC outlet.

Remove the antenna terminal on TV and turn on the TV.

Insulation resistance between the cord plug terminals and the eternal exposure metal [Note 2] should be more than 1M ohm by using the 500V insulation resistance meter [Note 1].

If the insulation resistance is less than 1M ohm, the inspection repair should be required.

[Note 1]

If you have not the 500V insulation resistance meter, use a Tester.

[Note 2]

External exposure metal: Antenna terminal

Earphone jack

HOW TO ORDER PARTS

Please include the following informations when you order parts. (Particularly the VERSION LETTER.)

1. MODEL NUMBER and VERSION LETTER The MODEL NUMBER can be found on the back of each product and the VERSION LETTER can be

found at the end of the SERIAL NUMBER.

2. PART NO. and DESCRIPTION You can find it in your SERVICE MANUAL.

IMPORTANT

Inferior silicon grease can damage IC's and transistors. When replacing an IC's or transistors, use only specified silicon grease (YG6260M). Remove all old silicon before applying new silicon.

GENERAL SPECIFICATIONS

G-1 TV CRT CRT Size / Visual Size 20 inch / 508.0mmV

G-2 Tuning Broadcasting System US System M

G-3 Power Power Source AC 120V AC 60Hz

G-4 Regulation Safety UL

G-5 Temperature Operation +5oC ~ +40oC

G-6 Operating Humidity Less then 80% RH

System CRT Type Normal

Color System NTSC Speaker 2Speaker

Sound Output MAX

NTSC3.58+4.43 /PAL60Hz No

System Tuner and System 1Tuner

Receive CH Destination Ohers

Intermediate Picture(FP) 45.75MHz Frequency Sound(FS) 41.25MHz

Preset CH No Stereo/Dual TV Sound Yes Tuner Sound Muting Yes

Power Consumption at AC

Protector Power Fuse Yes

Deflection Magnetic Field BV/BH +0.45G/0.18G

Position Front Size Impedance 8 ohm

10%(Typical)

Tuning System F-Synth Input Impedance VHF/UHF 75 ohm

CH Coverage A - I, J - W, W+1 - W+84

FP-FS 4.50MHz

Stand by (at AC) Per Year

Radiation FCC X-Radiation DHHS

Storage -20oC ~ +60oC

90 degree

2 x 4.7 Inch

2.5+2.5 W

2.0+2.0 W

90 W at AC 120 V 60 Hz 5 W at AC 120 V 60 Hz

-- kWh/Year

2 - 69, 4A, A-5 - A-1,

GENERAL SPECIFICATIONS

G-7 On Screen Menu Yes

G-8 OSD Language English French Spanish

G-9 Clock and Sleep Timer Max Time 120 Min

Display Menu Type Character

Timer Step

On/Off Timer Program(On Tim / Off Tim) Wake Up Timer Timer Back-up (at Power Off Mode) more than -- Min Sec

Picture Yes

Contrast Yes Brightness Yes Color Yes Tint Yes Sharpness Yes

Audio Yes

Bass Yes Treble Yes Balance Yes BBE On/Off No Stable Sound On/Off No

CH Set Up Yes

TV/CABLE(CATV) Yes Auto CH Memory Yes

Add/ Delete Yes Lock Yes Language Yes V-chip Yes

CH Label No

Favorite CH No

Color Stream DVD/DTV No Control Level Yes

Volume Yes

Brightness Yes

Contrast Yes

Color Yes

Tint (NTSC Only) Yes

Sharpness Yes

Tuning No

Bass Yes

Treble Yes

Balance Yes

Back Light No Stereo,Audio Output,SAP Yes Video Yes Color Stream No Channel(TV/Cable) Yes CH Label No Game Timer Yes Sleep Timer Yes Sound Mute Yes V-chip Rating Yes

OSD Language Setting English

10 Min

No No

GENERAL SPECIFICATIONS

G-10 Remote Unit RC-EH

Control Glow in Dark Remocon Yes

Format Toshiba Custom Code Power Source Voltage(D.C) 3V

UM size x pcs UM-4 x 2 pcs

Total Keys Keys Power Yes

1 Yes

2 Yes

3 Yes

4 Yes

5 Yes

6 Yes

7 Yes

8 Yes

9 Yes

0 Yes

100 No

CH Up Yes

CH Down Yes

Volume Up Yes

Volume Down Yes

TV/Caption/Text Yes

CH1/CH2 Yes

TV/Video(TV/AV) Yes

CH RTN/CH ENT(Quick View) Yes

Sleep Yes

RE Call(Call) Yes

Reset Yes

Menu Yes

Enter Yes

Mute Yes

Exit No

MTS(Audio Select) Yes

Set + Yes

Set - Yes

Multi Brand Keys CH Up(VCR) No

CH Down(VCR) No

Pause/Still No

TV/VCR(VCR) No

Code No

FF No

Rew No

Rec No

Play No

Stop No

TV No

VCR No

Cable No

40-BF h

28 Keys

GENERAL SPECIFICATIONS

G-11 Features Auto Degauss Yes

G-12 Accessories Owner's Manual Language English /French

Auto Shut Off Yes Canal+ No CATV Yes Anti-theft No Rental No Memory(Last CH) Yes Memory(Last Volume) Yes V-Chip Yes

BBE No Auto Search No CH Allocation No SAP Yes Just Clock Function No CH Label No VM Circuit No Full OSD No Premiere No Comb Filter Yes

Auto CH Memory Yes Hotel Lock No Closed Caption Yes Stable Sound No FBT Leak Test Protect Yes CH Lock Yes Video Lock Yes Game Timer Yes Energy Star No Favorite CH No

Remote Control Unit Yes Rod Antenna No

Loop Antenna

U/V Mixer DC Car Cord (Center+) Guarantee Card Warning Sheet Circuit Diagram Antenna Change Plug Service Facility List Important Safety Instruction Dew/AHC Caution Sheet AC Plug Adapter Quick Set-up Sheet Battery Yes

AC Cord AV Cord (2Pin-1Pin) Registration Card (NDL Card) Yes ESP Card Yes PTB Sheet 300 ohm to 75 ohm Antenna Adapter

Type

W/ Warranty Yes

Poles

Terminal

UM size x pcs UM4 x 2

OEM Brand

USA,ORION Type

2 Lines

No No No No No No No No No No No

No No No

No No

GENERAL SPECIFICATIONS

(

)

(

)

dges / 6 Surfaces

G-13 Interface Switch Front Power Yes

Rear AC/DC No

Indicator Power Yes

Terminals Front Video Input

Rear Video Input(Rear1)

G-14 Set Size Approx. W x D x H (mm) G-15 Weight Net (Approx.)

G-16 Carton Master Carton

Gift Box Yes

Drop Test

Container Stuffing

G-17 Cabinet Material Cabinet Front PS 94V0 DECABROM

System Select No

Main Power SW No

Sub Power No

Channel Up/Reset Yes

Channel Down/Enter Yes

Volume Up/Set Up Yes

Volume Down/Set Down Yes

MENU=Volume Up+Volume Down Yes

TV/CATV Selector No

Degauss No

Main Power SW No

Stand-by No

On Timer No

Audio Input

Other Terminal

Video Input(Rear2)

Audio Input(Rear1)

Audio Input(Rear2)

Video Output

Audio Output

Euro Scart

Color Stream

Diversity No

Ext Speaker No

DC Jack 12V(Center +) No

VHF/UHF Antenna Input

AC Outlet No

Gross (Approx.) 22.1kg

Content

Material

Dimensions W x D x H(mm)

Description of Origin

Material Double/Brown

Dimensions W x D x H(mm)

Design As per Buyer's

Description of Origin Yes

Height (cm) 46

Cabinet Rear PS 94V0 DECABROM

RCA RCA x 2 Head phone RCA

RCA x 2

F Type 590 x 492 x 446.5

18.6kg

----

-- x -- x --

658 x 575 x 529

Natural Dropping At 1

288

No No No No No

41.0 lbs

48.7 lbs No Sets /--

Sets/40' container

orner / 3

DISASSEMBLY INSTRUCTIONS

1. REMOVAL OF ANODE CAP

Read the following NOTED items before starting work. *

After turning the power off there might still be a potential voltage that is very dangerous. When removing the Anode Cap, make sure to discharge the Anode Cap's potential voltage.

Do not use pliers to loosen or tighten the Anode Cap terminal, this may cause the spring to be damaged.

REMOVAL

1. Follow the steps as follows to discharge the Anode Cap.

(Refer to Fig. 1-1.)

Connect one end of an Alligator Clip to the metal part of a flat-blade screwdriver and the other end to ground. While holding the plastic part of the insulated Screwdriver, touch the support of the Anode with the tip of the Screwdriver. A cracking noise will be heard as the voltage is discharged.

GND on the CRT

3. After one side is removed, pull in the opposite direction to remove the other.

NOTE

Take care not to damage the Rubber Cap.

INSTALLATION

1. Clean the spot where the cap was located with a small amount of alcohol. (Refer to Fig. 1-3.)

Location of Anode Cap

Fig. 1-3

NOTE

Confirm that there is no dirt, dust, etc. at the spot where the cap was located.

2.3.Arrange the wire of the Anode Cap and make sure the wire is not twisted. Turn over the Rubber Cap. (Refer to Fig. 1-4.)

Screwdriver

Alligator Clip

GND on the CRT

Flip up the sides of the Rubber Cap in the direction of the

2. arrow and remove one side of the support.

(Refer to Fig. 1-2.)

Rubber Cap

CRT

Support

CRT

Fig. 1-1

Fig. 1-2

Fig. 1-4

4. Insert one end of the Anode Support into the anode button, then the other as shown in Fig. 1-5.

Support

CRT

5.6.Confirm that the Support is securely connected. Put on the Rubber Cap without moving any parts.

Fig. 1-5

DISASSEMBLY INSTRUCTIONS

REMOVAL AND INSTALLATION OF FLAT PACKAGE IC

REMOVAL

Put the Masking Tape (cotton tape) around the Flat

1. Package IC to protect other parts from any damage.

(Refer to Fig. 2-1.) NOTE

Masking is carried out on all the parts located within 10 mm distance from IC leads.

When IC starts moving back and forth easily after

3. desoldering completely, pickup the corner of the IC using a tweezers and remove the IC by moving with the IC desoldering machine. (Refer to Fig. 2-3.)

NOTE

Some ICs on the PCB are affixed with glue, so be careful not to break or damage the foil of each IC leads or solder lands under the IC when removing it.

Blower type IC desoldering machine

Masking Tape (Cotton Tape)

Heat the IC leads using a blower type IC desoldering

machine. (Refer to Fig. 2-2.)

NOTE

Do not add the rotating and the back and forth directions force on the IC, until IC can move back and forth easily after desoldering the IC leads completely.

Blower type IC desoldering machine

Fig. 2-1

Tweezers

Peel off the Masking Tape.4. Absorb the solder left on the pattern using the Braided

5. Shield Wire. (Refer to Fig. 2-4.)

NOTE

Do not move the Braided Shield Wire in the vertical direction towards the IC pattern.

Fig. 2-3

Braided Shield Wire

Soldering Iron

Fig. 2-2

IC pattern

Fig. 2-4

DISASSEMBLY INSTRUCTIONS

INSTALLATION

Take care of the polarity of new IC and then install the new

1. IC fitting on the printed circuit pattern. Then solder each lead on the diagonal positions of IC temporarily.

(Refer to Fig. 2-5.)

Soldering Iron

Solder temporarily

Supply the solder from the upper position of IC leads

2. sliding to the lower position of the IC leads. (Refer to Fig. 2-6.)

Solder temporarily

Fig. 2-5

When bridge-soldering between terminals and/or the

4. soldering amount are not enough, resolder using a Thin-tip Soldering Iron. (Refer to Fig. 2-8.)

Thin-tip Soldering Iron

Fig. 2-8

Finally, confirm the soldering status on four sides of the IC

5. using a magnifying glass. Confirm that no abnormality is found on the soldering position and installation position of the parts around the IC. If some abnormality is found, correct by resoldering.

NOTE

When the IC leads are bent during soldering and/or repairing, do not repair the bending of leads. If the bending of leads are repaired, the pattern may be damaged. So, be always sure to replace the IC in this case.

Soldering IronSolder

Supply soldering from upper position to lower position

Fig. 2-6

Absorb the solder left on the lead using the Braided Shield

3. Wire. (Refer to Fig. 2-7.)

NOTE

Do not absorb the solder to excess.

Soldering Iron

Braided Shield Wire

Fig. 2-7

SERVICE MODE LIST

This unit provided with the following SERVICE MODES so you can repair, examine and adjust easily. To enter the Service Mode, press both set key and remote control key for more than 1 second.

Set Key

VOL. (-) MIN

VOL. (-) MIN 8

VOL. (-) MIN

Remocon Key

Releasing of V-CHIP PASSWORD and LOCK PASSWORD. Initialization of the factory.

NOTE:

POWER ON total hours is displayed on the screen. Refer to the "CONFIRMATION OF HOURS USED".

Can be checked of the INITIAL DATA of MEMORY IC. Refer to the "WHEN REPLACING EEPROM (MEMORY) IC".

Writing of EEPROM initial data. NOTE: Do not use this for the normal servicing.

Display of the Adjustment MENU on the screen. Refer to the "ELECTRICAL ADJUSTMENT" (On-Screen Display Adjustment).

Do not use this for the normal servicing. If you set a factory initialization, the memories are reset such as the channel setting, and the POWER ON total hours.

Operations

CONFIRMATION OF HOURS USED

POWER ON total hours can be checked on the screen. Total hours are displayed in 16 system of notation.

NOTE: If you set a factory initialization, the total hours is reset to "0".

Set the VOLUME to minimum.

Press both VOL. DOWN button on the set and Channel button (6) on the remote control for more than 1 second.

After the confirmation of using hours, turn off the power.

ADDRESS DATA

INIT 00 08 CRT ON 0010

FIG. 1

Initial setting content of MEMORY IC. POWER ON total hours.

= (16 x 16 x 16 x thousands digit value) + (16 x 16 x hundreds digit value) + (16 x tens digit value) + (ones digit value)

WHEN REPLACING EEPROM (MEMORY) IC

If a service repair is undertaken where it has been required to change the MEMORY IC, the following steps should be taken to ensure correct data settings while making reference to TABLE 1.

INI

+0 +1 +2 +3 +4 +5 +6 +7 +8 +9 +A +B +C +D +E +F

00 44 20 0C 4B 4B 9B

08 60 C9 0A 09 B3 24 6B 8B 00 62 26 27 67 28 68 29 69 4A10 25 6A 4B 6B 4C 6C 4D

6D 4F 6F 50 70 51 71 52 7220 4E 53 73 54 74 55 75

56 57 57 77 77 58 58 78 7830 76 59 59 79 79 5A 5A

7A 5B 5B 7B 7B 5C 5C 7C 7C40 7A 5D 5D 5D 7D 7D 7D

Table 1

Enter DATA SET mode by setting VOLUME to minimum.

Press both VOL. DOWN button on the set and Channel button (6) on the remote control for more than 1 second. ADDRESS and DATA should appear as FIG 1.

ADDRESS is now selected and should "blink". Using the SET +/- button on the remote, step through the ADDRESS until required ADDRESS to be changed is reached.

Press ENTER to select DATA. When DATA is selected, it will "blink".

Again, step through the DATA using SET +/- button until required DATA value has been selected.

Pressing ENTER will take you back to ADDRESS for further selection if necessary.

Repeat steps 3 to 6 until all data has been checked.

When satisfied correct DATA has been entered, turn POWER off (return to STANDBY MODE) to finish DATA input.

The unit will now have the correct DATA for the new MEMORY IC.

ELECTRICAL ADJUSTMENTS

BEFORE MAKING ELECTRICAL ADJUSTMENTS

Read and perform these adjustments when repairing the circuits or replacing electrical parts or PCB assemblies.

CAUTION

Use an isolation transformer when performing any service

•

on this chassis. Before removing the anode cap, discharge electricity

•

because it contains high voltage. When removing a PCB or related component, after

•

unfastening or changing a wire, be sure to put the wire back in its original position. When you exchange IC and Transistor for a heat sink, apply

•

the silicon grease on the contact section of the heat sink. Before applying new silicon grease, remove all the old silicon grease. (Old grease may cause damages to the IC and Transistor.)

Prepare the following measurement tools for electrical adjustments.

1. Oscilloscope

2. Digital Voltmeter

3. Multi-sound Generator

4. Pattern Generator

On-Screen Display Adjustment

In the condition of NO indication on the screen.

Press the VOL. DOWN button on the set and the Channel button (9) on the remote control for more than 1 second to appear the adjustment mode on the screen as shown in Fig. 1-1.

00 OSD 15

Fig. 1-1

Use the Channel UP/DOWN button or Channel button (0-

9) on the remote control to select the options shown in Fig. 1-2.

Press the ACTION button on the remote control to end

the adjustments.

2. BASIC ADJUSTMENTS

2-1: CONSTANT VOLTAGE

Place the set with Aging Test for more than 15 minutes.

Set condition is AV MODE without signal.

Using the remote control, set the brightness and contrast to normal position.

Connect the digital voltmeter to the TP402.

Adjust the VR502 until the digital voltmeter is 130 ± 1V.

2-2: RF AGC

Place the set with Aging Test for more than 15 minutes.

1. Receive the VHF HIGH (63dB).

2. Connect the digital voltmeter to the TP001.

3. Activate the adjustment mode display of Fig. 1-1 and

4. press the channel button (02) on the remote control to select "RF.AGC". Press the VOL. UP/DOWN button on the remote control

5. until the digital voltmeter is 2.5 ± 0.05V.

2-3: CUT OFF

Adjust the unit to the following settings. R.DRIVE=10, B.DRIVE=10, R.BIAS=64, G.BIAS=64, B.BIAS=64, BRIGHTNESS=124, CONTRAST=65.

Place the set with Aging Test for more than 15 minutes.

Activate the adjustment mode display of Fig. 1-1 and press the channel button (01) on the remote control to select "CUT OFF".

Adjust the Screen Volume until a dim raster is obtained.

2-4: WHITE BALANCE NOTE: Adjust after performing CUT OFF adjustment.

Place the set with Aging Test for more than 10 minutes.

Receive the gray scale pattern from the Pattern Generator.

Using the remote control, set the brightness and contrast to normal position.

Activate the adjustment mode display of Fig. 1-1 and press the channel button (10) on the remote control to select “R. BIAS”.

Press the CH. UP/DOWN button on the remote control to select the “R. BIAS”, “G. BIAS”, “B. BIAS”, “R. DRIVE” or “B. DRIVE”.

Adjust the VOL. UP/DOWN button on the remote control to whiten the R. BIAS, G. BIAS, B. BIAS, R. DRIVE, and B. DRIVE at each step tone sections equally.

Perform the above adjustments 5 and 6 until the white color is looked like a white.

FUNCTION

NO.

OSD H

CUT OFF

RF AGC

VIF VCO

H.VCO

H.PHASE

V.SIZE

V.SHIFT

R.DRIVE

B.DRIVE

R.BIAS

G.BIAS

B.BIAS

BRIGHT CENT

BRIGHT MAX

BRIGHT MIN

FUNCTION

NO.

CONTRAST CENT

CONTRAST MAX

CONTRAST MIN

COLOR CENT

COLOR MAX

COLOR MIN

TINT

SHARPNESS

FM LEVEL

LEVEL

SEPARATION 1

SEPARATION 2

TEST MONO

TEST STEREO

X-RAY TEST

Fig. 1-2

2-5: FOCUS

Receive a broadcast.

Turn the Focus Volume fully counterclockwise once.

Adjust the Focus Volume until picture is distinct.

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