Toshiba 14AS20 Schematic
FILE NO. 063-200006
SERVICE MANUAL
COLOR TELEVISION
N0E Chassis
14AS20
(TAC0002)
– SUMMARY –
14AS20 is the same as 19A20 except for the parts and setting & adjusting data tabled
on back of this sheet.
Use this service manual together with the service manual of 19A20 (File No. 020-200003).
PUBLISHED IN JAPAN, Aug., 2000 So
SETTING & ADJUSTING DATA DIFFERENCES
SAFETY INSTRUCTIONS
CIRCUIT CHECKS
REPLACEMENT PARTS LIST DIFFERENCES
14"
HIGH VOLTAGE AT ZERO BEAM: (A) 23.5 kV
MAX HIGH VOLTAGE:
(B) 24.9 kV
Table-1
FBT DETECTION VOLTAGE (C) 21.02V
Table-4
Location
No.
A201 23549359 Front Cover
A401 23003326 Back Cover
A701 23525144 Case
A702A 23935906 Packing
A702B 23935907 Packing
C230 24794470 EL, 47?F, ±20%, 16V
C310 24796470 EL, 47?F, ±20%, 35V
C311 24214101 CD, 100pF, ±10%, 500V
C440 24082952 PF, 6200pF, ±3%, 1500V
C611 24591104 PF, 0.1?F
C810 24086939 EL, 330?F, ±20%, 200V
D472 23115774 Diode, Zener, RD6.2E(4)
E502 23848729 Rubber Wedge
L462 23231183 Deflection Yoke, TDY-314QY
L901 23200306 Coil, Degaussing, TSB-2219AL
M051Z Main Board, PB9391B1
*
M052Z CRT Drive Board, PB9391B2
*
P801 23372123 Power Cord
R227 24366473 CF, 47k ohm
R304 24366473 CF, 47k ohm
R305 24322159 MF, 1.5 ohm, 1W
R306 24366683 CF, 68k ohm
R307 24366474 CF, 470k ohm
R312 24381222 OMF, 2200 ohm, 1/2W
R313 24366274 CF, 270k ohm
Part No. Description
Location
No.
R317 24366243 CF, 24k ohm
R327 24338689 MF, 6.8 ohm, 1W
R416 24019327 OMF, 2700 ohm, 5W
R475 24367821 CF, 820 ohm, ±2%
R802 24376274 CF, 270k ohm, 1/2W
R808 24000209 PTC Thermistor, 14 ohm,
R810 24510229 Cement, 2.2 ohm, 5W
R811 24569241 Cement, 240 ohm, 10W
R812 24510689 Cement, 6.8 ohm, 5W
R920 24000568 FR, 4.7 ohm, 1W
R921 24366471 CF, 470 ohm
R922 24366471 CF, 470 ohm
R923 24366471 CF, 470 ohm
R931 24366122 CF, 1200 ohm
R932 24366122 CF, 1200 ohm
R933 24366122 CF, 1200 ohm
T461 23236589 Transformer, Flyback,
V901 23312577 Picture Tube, A34JFQ90X(VW)
V901M 23102409 Magnet, Purity-Convergence,
Y101 23565007 Owner’s Manual,
Part No. Description
±20%, AC140V
TFB4139AY
MAG-1070
English/Spanish, 14AS20
TOSHIBA CORPORATION
1-1, SHIBAURA 1-CHOME, MINATO-KU, TOKYO 105-8001, JAPAN
FILE NO. 020-200003
SERVICE MANUAL
COLOR TELEVISION
N0E Chassis
19A20
(TAC0001)
PRINTED IN U.S.A. Mar., 2000 U
CHAPTER 1 GENERAL ADJUSTMENTS
SAFETY INSTRUCTIONS........................................................................................................................................3
SET-UP ADJUSTMENT............................................................................................................................................4
SERVICE MODE ...................................................................................................................................................... 8
DESIGN MODE ...................................................................................................................................................... 11
ELECTRICAL ADJUSTMENTS ..............................................................................................................................12
CIRCUIT CHECKS .................................................................................................................................................14
GENERAL ADJUSTMENTSSPECIFIC INFORMATIONS
CHAPTER 2 SPECIFIC INFORMATIONS
SETTING & ADJUSTING DATA ............................................................................................................................. 15
LOCATION OF CONTROLS................................................................................................................................... 16
PROGRAMMING CHANNEL MEMORY.................................................................................................................17
CIRCUIT BLOCK DIAGRAM ..................................................................................................................................18
CHASSIS AND CABINET REPLACEMENT PARTS LIST......................................................................................19
PC BOARDS BOTTOM VIEW ................................................................................................................................23
TERMINAL VIEW OF TRANSISTORS ................................................................................................................... 26
TABLE OF CONTENTS
SPECIFICATIONS ..................................................................................................................................................29
APPENDIX:
CIRCUIT DIAGRAM
– 2 –
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 abov e the specified limit. The nominal
value of the high voltage of this receiver is (A) kV at zero
beam current (minimum brightness) under a 120V AC
power source. The high voltage must not, under any circumstances, exceed (B) kV.
Refer to table-1 for high voltage (A), (B).
(See SETTING & ADJUSTING DATA on page 15)
Each time a receiver requires servicing, the high voltage
should be checked f ollowing the HIGH VOLTAGE CHECK
procedure in this manual. It is recommended that the reading 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.
SAFETY PRECAUTION
2. This receiver is equipped with a Fail Safe (FS) circuit which
prevents the receiver from producing an excessively high
voltage ev en if the B+ voltage increases abnormally. Each
time the receiver is serviced, the FS circuit must be checked
to determine that the circuit is properly functioning, following the FS CIRCUIT CHECK procedure in this manual.
3. The only source of X-RAY RADIA TION in this TV receiver
is the picture tube. F or contin ued X-RAY RADIATION protection, the replacement tube must be exactly the same
type tube as specified in the parts list.
4. Some part in this receiver have special safety-related characteristics for X-RAY RADIATION protection. For continued safety, parts replacement should be undertaken only
after referring to the PRODUCT SAFETY NO TICE below.
GENERAL ADJUSTMENTSSPECIFIC INFORMATIONS
WARNING : Service should not be attempted by any one unf amiliar with the necessary precautions on this receiver. The following are the necessary precautions to be observed before
servicing this chassis.
1. An isolation Transf ormer should be connected in the power
line between the receiver and the AC line bef ore an y service is performed on the receiver.
2. Always discharge the picture tube anode to the CR T 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.
4. Before returning the set to the customer, always perform
an AC leakage current check on the e xposed metallic parts
of the cabinet, such as antennas, terminals, screwheads,
metal overlays, control shafts etc. to be sure the set is
safe to operate without danger of electrical shock. Plug
the AC line cord directly into a 120V AC outlet (do not use
a line isolation transformer during this check). Use an AC
voltmeter having 5000 ohms per volt or more sensitivity in
the following manner:
Connect a 1500 ohm 10 watt resistor, paralleled b y a 0.15
µF, AC type capacitor, between a known good earth ground
(water pipe, conduit, etc.) and the exposed metallic parts,
one at a time. Measure the AC voltage across the combination of 1500 ohm resistor and 0.15 µF capacitor. Reverse the AC plug at the AC outlet and repeat AC voltage
measurements for each exposed metallic part. Voltage
measured must not exceed 0.3 v olts rms. This corresponds
to 0.2 milliamp. AC. Any value exceeding this limit constitutes a potential shock hazard and must be corrected immediately.
AC VOLTMETER
0.15µF
Place this probe on
Good earth ground
such as a water
pipe, conduit, etc.
1500 ohm
10 watt
each exposed
metallic part.
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 b y using
replacement components rated for higher voltage, wattage, etc. Replacement parts which have these special safety characteristics 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.
– 3 –
WARNING: BEFORE SERVICING THIS CHASSIS, READ THE “X-RAY RADIATION PRECAUTION”, “SAFETY PRECAUTION” AND “PRODUCT SAFETY NOTICE” ON PAGE 3 OF THIS MANUAL.
SET-UP ADJUSTMENT FOR 13", 14", 19", 20".
■ 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.
GENERAL ADJUSTMENTSSPECIFIC INFORMATIONS
*
COLOR PURITY ADJUSTMENT
NOTE : Before attempting any purity adjustments, the receiver
1. Demagnetize the picture tube and cabinet using a degauss-
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
Refer to figure 1.
Mounting position of the purity magnet assembly should fit to same position as old one because slightly difference to
the position depend on a kind of tube.
There are no adjustment of purity and convergence in some picture tube (Unified with purity magnet)
should be operated for at least fifteen minutes.
ing coil.
yoke backward or forward to provide vertical green belt
(zone) in the picture screen.
SET-UP ADJUSTMENT
5. Remove the Rubber Wedges.
6. Rotate and spread the tabs of the purity magnet (See figure 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
14mm(13", 14")
19mm(19", 20")
PURITY/
CONVERGENCE
MAGNET ASS'Y
TEMPORARY
MOUNTING
RUBBER WEDGE
ADHESIVE
DEFLECTION
YOKE
Figure 1.
– 4 –
CONVERGENCE ADJUSTMENTS
NOTE: Before attempting any convergence adjustments, the
receiver should be operated for at least fifteen minutes.
■ CENTER CONVERGENCE ADJUSTMENT
1. Use the cross-dot pattern from among the built-in test signals.
2. Set the brightness and contrast for well defined pattern.
3. Adjust two tabs of the 4-Pole Magnets to change the angle 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 horizontal 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.
4-POLE
MAGNETS
6-POLE
MAGNETS
ADJUST THE ANGLE
(VERTICAL LINES)
■ 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 convergence 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 another 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 y oke
is firm.
9. Stick three adhesive tapes on wedges as shown in figure
1.
FIXED
GENERAL ADJUSTMENTSSPECIFIC INFORMATIONS
ROTATE TWO TABS
AT THE SAME TIME
(HORIZONTAL LINES)
PURITY
MAGNETS
CONVERGENCE MAGNET ASSEMBLY ADJUSTMENT OF MAGNETS
Figure 2.
BLU RED
BLU
RED
4-POLE MAGNETS MOVEMENT
BGR
R
G
B
RGB
RED/BLU
GRN
Center Convergence by Convergence Magnets
B
G
R
RED/BLU GRN
6-POLE MAGNETS MOVEMENT
B
G
R
BGR
RGB
R
G
B
INCLINE THE YOKE UP (OR DOWN)
Circumference Convergence by DEF Yoke
Figure 3. Dot Movement Pattern
INCLINE THE YOKE RIGHT (OR LEFT)
– 5 –
WARNING: BEFORE SERVICING THIS CHASSIS, READ THE “X-RAY RADIATION PRECAUTION”, “SAFETY PRECAUTION” AND “PRODUCT SAFETY NOTICE” ON PAGE 3 OF THIS MANUAL.
SET-UP ADJUSTMENT FOR 35", 36".
■ 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.
GENERAL ADJUSTMENTSSPECIFIC INFORMATIONS
*
COLOR PURITY ADJUSTMENT
NOTE : Before attempting any purity adjustments, the
1. Evenly degauss the entire screen.
2. Set the CONTRAST and BRIGHTNESS Controls to
3. Display built-in green raster using the TEST SIGNAL
4. Loosen the clamp screw holding the deflection yoke
5. Slide the yoke forward or backward to provide vertical
6. Rotate and spread the tabs of the purity magnet (See
Mounting position of the purity magnet assembly should fit to same position as old one because slightly difference to
the position depend on a kind of tube.
There are no adjustment of purity and convergence in some picture tube (Unified with purity magnet)
receiver should be operated for at least fifteen
minutes.
the maximum.
SELECTION function.
(and remove the Rubber Wedges).
green belt (zone) in the picture screen.
figure 4.) around the neck of the picture tube until the
green belt is in the center of the screen. At the same
time, center the raster vertically by adjusting the magnet as shown below.
Xv Coil
DEFLECTION YOKE
1-5/8"
PURITY/
CONV.
MAGNET
Green Belt
7. Move the yoke slowly forward or backward until a uniform green screen is obtained. Tighten the clamp scre w
of the yoke temporarily.
8. Check the purity of the red and blue raster.
9. Put four wedges into the space between the picture
tube and the yoke to hold the yoke in the adjusted
position. (See figure 2.)
Do not tilt the yoke by excessive insertion of the wedge.
10. Remove cover paper of wedge and stick wedges on
the tube to fix the yoke in the adjusted position.
Fix the wedges with glass cloth tapes.
Figure 1.
RUBBER WEDGES
Adhesive
DEFLECTION
YOKE
Figure 2.
– 6 –
CONVERGENCE ADJUSTMENTS
NOTE: Before attempting any convergence adjustments,
the receiver should be operated for at least fifteen
minutes.
■ CENTER CONVERGENCE ADJUSTMENT
1. Display built-in cross-dot pattern using the TEST SIGNAL SELECTION function.
2. Adjust the BRIGHTNESS and CONTRAST Controls
for well defined pattern.
3. Loosen the tightening ring and adjust two tabs of the
4-Pole Magnets to change the angle between them
(See figure 4.) and superimpose red and blue vertical
lines in the center area of the picture screen.
(See figure 3.)
4. Turn the both tabs at the same time keeping the constant angle to superimpose red and blue horizontal
lines at the centre of the screen. (See figure 3.)
5. Adjust two tabs of 6-Pole Magnets to superimpose red/
blue line with green one. Adjusting the angle affects
the vertical lines and rotating both magnets affects the
horizontal lines.
6. Repeat adjustments 3, 4, 5 keeping in mind red, green
and blue movement, because 4-Pole Magnets and 6Pole magnets interact and make dot movement complex.
7. After completing the “CENTER CONVERGENCE ADJUSTMENT” tighten the tightening ring to fix the magnets.
BLU RED
RED/BLUE GRN
6-POLE
MAGNETS
PURITY
MAGNETS
ADJUST THE ANGLE
(VERTICAL LINES)
4-POLE
MAGNETS
PURITY/CONVERGENCE
MAGNETS
FIXED
ROTATE TWO TABS
AT THE SAME TIME
(HORIZONTAL LINES)
ADJUSTMENT OF MAGNETS
GENERAL ADJUSTMENTSSPECIFIC INFORMATIONS
BLU
RED
4-POLE MAGNETS
MOVEMENT
Center Convergence by Convergence Magnets
■ Xv COIL ADJUSTMENT
Adjust the Xv coil (on the deflection yoke) to correct
misconvergence at both sides on screen.
Use a hexagonal tip stick (plastic) to adjust the core of
coil.
Clockwise Adjustment Counterclockwise Adjustment
R
B
RED/BLUE
Figure 3.
B
R
GRN
6-POLE MAGNETS
MOVEMENT
B
R
R
B
Figure 4.
■ SCREEN-CORNER CONVERGENCE
When the misconvergence is still evident on corners even
though the above adjustment is done, use the ferrite sheet
(Part No. 23993622) to correct misconvergence.
1. Put ferrite sheets into the space under the yoke.
Decide such position that misconvergence becomes
minimum, watching picture screen. (See figure below .)
2. Remove cover paper of ferrite sheet to stick it in the
place on the tube. Put adhesive tapes on ferrite sheets
to fix.
Ferrite
Sheets
Ferrite
Sheets
A
Xv Cross Pattern View
For correcting misconvergence
on the position A
– 7 –
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