TOSHIBA 28N03B - Service Manual Immediate Download

TOSHIBA CORPORATION

1-1, SHIBAURA 1- CHOME, MINATO-KU, TOKYO 105-8001, JAPAN

SERVICE MANUAL

COLOUR TELEVISION

C0SS Chassis

FILE NO. 030-200003

PRINTED IN JAPAN.

Jun., 2000

28N03F, 28N03B

28N03D, 28N01F

GENERAL

ADJUSTMENTS

SPECIFIC

INFORMATIONS

TABLE OF CONTENTS

CHAPTER 1 GENERAL ADJUSTMENTS

SAFETY INSTRUCTIONS ........................................................................................................................................ 3

SET-UP ADJUSTMENT ............................................................................................................................................ 4

SERVICE MODE ...................................................................................................................................................... 6

ELECTRICAL ADJUSTMENTS .............................................................................................................................. 10

CIRCUIT CHECK .................................................................................................................................................... 15

CHAPTER 2 SPECIFIC INFORMATIONS

SETTING & ADJUSTING DATA .............................................................................................................................. 16

LOCATION OF CONTROLS ................................................................................................................................... 17

CHASSIS AND CABINET REPLACEMENT PARTS LIST ......................................................................................19

PC BOARDS BOTTOM VIEW ................................................................................................................................. 27

TERMINAL VIEW OF TRANSISTORS ................................................................................................................... 32

SPECIFICATIONS .................................................................................................................................................. 33

APPENDIX:

CIRCUIT DIAGRAM

GENERAL

ADJUSTMENTS

SPECIFIC

INFORMATIONS

PRODUCT SAFETY NOTICE

Many electrical and mechanical parts in this chassis have special safety-related characteristics. These characteristics are

often passed unnoticed by a visual inspection and the protection afforded by them cannot necessarily be obtained by using

replacement components rated for higher voltage, wattage, etc. Replacement parts which have these special safety char-

acteristics are identified in this manual and its supplements; electrical components having such features are identified by

the international hazard symbols on the schematic diagram and the parts list.

Before replacing any of these components, read the parts list in this manual carefully. The use of substitute replacement

parts which do not have the same safety characteristics as specified in the parts list may create shock, fire, X-ray radiation

or other hazards.

CHAPTER 1 GENERAL ADJUSTMENTS

SAFETY INSTRUCTIONS

WARNING: BEFORE SERVICING THIS CHASSIS, READ THE "X-RAY RADIATION PRECAUTION", "SAFETY PRECAU-

TION" AND "PRODUCT SAFETY NOTICE" INSTRUCTIONS BELOW.

X-RAY RADIATION PRECAUTION

1. Excessive high voltage can produce potentially hazardous

X-RAY RADIATION.To avoid such hazards, the high voltage

must not be above the specified limit. The nominal value of

the high voltage of this receiver is (A) kV at zero beam

current (minimum brightness) under a (C) V AC power

source. The high voltage must not, under any circum-

stances, exceed (B) kV.

Refer to table-1 for high voltage (A) , (B) & AC voltage (C).

(See SETTING & ADJUSTING DATA on page 16)

Each time a receiver requires servicing, the high voltage

should be checked following the HIGH VOLTAGE CHECK

procedure in this manual. It is recommended that the read-

ing of the high voltage be recorded as a part of the service

record. It is important to use an accurate and reliable high

voltage meter.

2. The only source of X-RAY RADIATION in this TV receiver

is the picture tube. For continued X-RAY RADIATION pro-

tection, the replacement tube must be exactly the same

type tube as specified in the parts list.

3. Some part in this receiver have special safety-related char-

acteristics for X-RAY RADIATION protection. For contin-

ued safety, parts replacement should be undertaken only

after referring to the PRODUCT SAFETY NOTICE below.

SAFETY PRECAUTION

WARNING : Service should not be attempted by anyone unfamiliar with the necessary precautions on this receiver. The follow-

ing are the necessary precautions to be observed before servicing this chassis.

1. An isolation transformer should be connected in the power line between the receiver and the AC line before any service is

performed on the receiver.

2. Always discharge the picture tube anode to the CRT conductive coating before handling the picture tube. The picture tube

is highly evacuated and if broken, glass fragments will be violently expelled. Use shatter proof goggles and keep picture

tube away from the unprotected body while handling.

3. When replacing a chassis in the cabinet, always be certain that all the protective devices are put back in place, such as; non-

metallic control knobs, insulating covers, shields, isolation resistor-capacitor network etc.

GENERAL

ADJUSTMENTS

SPECIFIC

INFORMATIONS

WARNING: BEFORE SERVICING THIS CHASSIS, READ THE "X-RAY RADIATION PRECAUTION", "SAFETY PRECAU-

TION" AND "PRODUCT SAFETY NOTICE" ON PAGE 3 OF THIS MANUAL.

SET-UP ADJUSTMENT

s The following adjustments should be made when a complete realignment is required or a new picture tube is installed.

Perform the adjustments in order as follows :

1. Color Purity

2. Convergence

3. White Balance

Note: The PURITY/CONVERGENCE MAGNET assembly and rubber wedges need mechanical positioning.

Refer to figure 1.

Mounting position of the purity magnet assembly should fit to same position as old one because slightly difference to

the postition depend on a kind of tube.

* There are no adjustment of purity and convergence in some picture tube (Unified with purity magnet)

Figure 1.

COLOR PURITY ADJUSTMENT

NOTE : Before attempting any purity adjustments, the receiver

should be operated for at least fifteen minutes.

1. Demagnetize the picture tube and cabinet using a degauss-

ing coil.

2. Set the brightness and contrast to maximum.

3. Use a green raster from among the built-in test signals.

4. Loosen the clamp screw holding the yoke and slide the

yoke backward or forward to provide vertical green belt

(zone) in the picture screen.

5. Remove the Rubber Wedges.

6. Rotate and spread the tabs of the purity magnet (See fig-

ure 2.) around the neck of the picture tube until the green

belt is in the center of the screen. At the same time, enter

the raster vertically.

7. Slowly move the yoke forward or backward until a uniform

green screen is obtained. Tighten the clamp screw of the

yoke temporarily.

8. Check the purity of the red and blue raster.

GLASS CLOTH

TAPES

DEFLECTION

YOKE

TEMPORARY

MOUNTING

RUBBER WEDGE

ADHESIVE

DEFLECTION

YOKE

PURITY/

CONVERGENCE

MAGNET ASS'Y

29.1mm(28", 29")

25mm(25")

19mm(19", 20", 21")

14mm(13", 14")

GENERAL

ADJUSTMENTS

SPECIFIC

INFORMATIONS

CONVERGENCE ADJUSTMENTS

NOTE: Before attempting any convergence adjustments, the

receiver should be operated for at least fifteen min-

utes.

CENTER CONVERGENCE ADJUSTMENT

1. Use the cross-dot pattern from among the built-in test sig-

nals.

2. Set the brightness and contrast for well defined pattern.

3. Adjust two tabs of the 4-Pole Magnets to change the an-

gle between them (See figure 2.) and superimpose red

and blue vertical lines in the center area of the picture

screen.

4. Turn the both tabs at the same time keeping the angle

constant to superimpose red and blue horizontal lines at

the center of the screen.

5. Adjust two tabs of 6-Pole Magnets to superimpose red/

blue line and green one. Adjusting the angle affects the

vertical lines and rotating both magnets affects the hori-

zontal lines.

6. Repeat adjustments 3, 4, 5 keeping in mind red, green

and blue movement, because 4-Pole Magnets and 6-Pole

Magnets have mutual interaction and make dot movement

complex.

CIRCUMFERENCE CONVERGENCE ADJUSTMENT

1. Loosen the clamping screw of deflection yoke slightly to

allow the yoke to tilt.

2. Temporarily put a wedge as shown in figure 1. (Do not

remove cover paper on adhesive part of the wedge.)

3. Tilt front of the deflection yoke up or down to obtain better

convergence in circumference. (See figure 3.) Push the

mounted wedge into the space between picture tube and

the yoke to fix the yoke temporarily.

4. Put other wedge into bottom space and remove the cover

paper to stick.

5. Tilt front of the yoke right or left to obtain better conver-

gence in circumference. (See figure 3.)

6. Keep the yoke position and put another wedge in either

upper space. Remove cover paper and stick the wedge

on picture tube to fix the yoke.

7. Detach the temporarily mounted wedge and put it in an-

other upper space. Stick it on picture tube to fix the yoke.

8. After fixing three wedges, recheck overall convergence.

Tighten the screw firmly to fix the yoke and check the yoke

is firm.

9. Stick three adhesive tapes on wedges as shown in figure

Figure 2.

Figure 3. Dot Movement Pattern

4-POLE

MAGNETS

PURITY

MAGNETS

6-POLE

MAGNETS

ADJUST THE ANGLE

(VERTICAL LINES)

FIXED

ROTATE TWO TABS

AT THE SAME TIME

(HORIZONTAL LINES)

CONVERGENCE MAGNET ASSEMBLY

ADJUSTMENT OF MAGNETS

BLU

RED

BLU

RED

RED/BLU GRN

RED/BLU

GRN

BGR

RGB

BGR

RGB

4-POLE MAGNETS MOVEMENT

INCLINE THE YOKE UP (OR DOWN)

6-POLE MAGNETS MOVEMENT

Center Convergence by Convergence Magnets

Circumference Convergence by DEF Yoke

INCLINE THE YOKE RIGHT (OR LEFT)