Changhong Electric 21BM91 User manual

FILE NO. SM-CTV-O-155
COLOR TELEVISION
SERVICE MANUAL
MODELNO.
CHASSIS NO. CN-18EA
Please read this manual carefully before service.
21BM91
(V2)

TABLE OF CONTENTS
SPECIFICATIONS............................................................................................................1
SAFETY INSTRUCTIONS AND MAINTENANCE.......................................2
X-RAY RADIATION PRECAUTION.........................................................................................2
SAFETY PRECAUTION ..........................................................................................................2
PRODUCT SAFETY NOTICE..................................................................................................3
SAFETY SYMBOL DESCRIPTION .........................................................................................4
MAINTENANCE.......................................................................................................................4
ADJUSTMENTS................................................................................................................5
SET-UP ADJUSTMENTS ........................................................................................................5
CIRCUIT ADJUSTMENTS.......................................................................................................8
STRUCTURE AND CHASSIS FUNCTION DESCRIPTION................. 24
STRUCTURE BLOCK DIAGRAM .........................................................................................24
BLOCK DIAGRAM FOR SUPPLY VOLTAGE SYSTEM .......................................................25
CHASSIS DESCRIPTION .....................................................................................................26
SERVICE DATA...............................................................................................................27
TECHNICAL DATA OF KEY ICS ..........................................................................................27
SERVICE DATA OF KEY ICS ............................................................................................... 51
REPLACEMENT OF PARTS................................................................................... 58
APPENDIX
1. CIRCUIT DIAGRAM
2. FINAL ASSEMBLY DIAGRAMS
3. FIND WIRING DIAGRAMS
4. PRINTED CIRCUIT BOARD LAYOUTS

SERVICE MANUAL
1
SPECIFICATIONS
Table 1 Specifications
Model Number
Color
system PAL, NTSC3.58, NTSC4.43, SECAM
RF system Sound
system B/G, D/K, I, M
Video system PAL4.43, NTSC3.58, NTSC4.43, SECAM (50/60Hz)
Channels preset 236 (0-235)
Antenna input 75 (unbalanced)
Picture tube
Effective screen dimensions
(Approx.)
406 305mm
Audio output
(THD 7%)
Power source 220V ~, 50Hz
Weight (Approx.)
Dimensions
(W HD) (Approx.) 590451475mm
Rated power consumption
(220V ~, 50Hz)
Designs and specifications are subject to change without notice.
21BM91
3W+3W
22kg
87W

SERVICE MANUAL
SAFETY INSTRUCTIONS AND MAINTENANCE
WARNING: BEFORE SERVICING THIS CHASSIS, READ THE “ X-RAY RADIATION
PRECAUTION ” , “ SAFETY PRECAUTION ” AND “ PRODUCT SAFETY NOTICE ” INSTRUCTION
BELOW.
X-RAY RADIATION PRECAUTION
1. The EHT must be checked every time the TV is serviced to ensure that the CRT does not emit
X-ray radiation as result of excessive EHT voltage. The maximum EHT voltage permissible in any
operating circumstances must not exceed the rated value. When checking the EHT, use the High
Voltage Check procedure in this manual using an accurate EHT voltmeter.
2. The only source of X-RAY radiation in this TV is the CRT. The TV minimizes X-RAY radiation,
which ensures safety during normal operation. To prevent X-ray radiation, the replacement CRT
must be identical to the original fitted as specified in the parts list.
3. Some components used in this TV have safety related characteristics preventing the CRT from
emitting X-ray radiation. For continued safety, replacement component should be made after
referring the PRODUCT SAFETY NOTICE below.
4. Service and adjustment of the TV may result in changes in the nominal EHT voltage of the CRT
anode. So ensure that the maximum EHT voltage does not exceed the rated value after service
and adjustment.
SAFETY PRECAUTION
WARNING: REFER SERVICING TO QUALIFIED SERVICE PERSONNEL ONLY.
1. The TV has a nominal working EHT voltage. Extreme caution should be exercised when working
on the TV with the back removed.
1.1 Do not attempt to service this TV if you are not conversant with the precautions and procedures for
working on high voltage equipment.
1.2 When handling or working on the CRT, always discharge the anode to the TV chassis before
removing the anode cap in case of electric shock.
1.3 The CRT, if broken, will violently expel glass fragments. Use shatterproof goggles and take
extreme care while handling.
1.4 Do not hold the CRT by the neck as this is a very dangerous practice.
2. It is essential that to maintain the safety of the customer all power cord forms be replaced exactly
as supplied from factory.
3. Voltage exists between the hot and cold ground when the TV is in operation. Install a suitable
isolating transformer of beyond rated overall power when servicing or connecting any test
equipment for the sake of safety.
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SERVICE MANUAL
4. When replacing ICs, use specific tools or a static-proof electric iron with small power (below 35W).
5. Do not use a magnetized screwdriver when tightening or loosing the deflection yoke assembly to
avoid electronic gun magnetized and decrement in convergence of the CRT.
6. When remounting the TV chassis, ensure that all guard devices, such as nonmetal control buttons,
switch, insulating sleeve, shielding cover, isolating resistors and capacitors, are installed on the
original place.
7. Replace blown fuses within the TV with the fuse specified in the parts list.
8. When replacing wires or components to terminals or tags, wind the leads around the terminal
before soldering. When replacing safety components identified by the international hazard symbols
on the circuit diagram and parts list, it must be the company-approved type and must be mounted
as the original.
9. Keep wires away from high temperature components.
PRODUCT SAFETY NOTICE
CAUTION: FOR YOUR PROTECTION, THE FOLLOWING PRODUCT SAFETY NOTICE
SHOULD BE READ CAREFULLY BEFORE OPERATING AND SERVICING THIS TV SET.
1. Many electrical and mechanical components in this chassis have special safety-related
characteristics. These characteristics are often passed unnoticed by a visual inspection and the
X-ray radiation protection afforded by them cannot necessarily be obtained by using replacements
rated at higher voltages or wattage, etc. Components which have these special safety
characteristics in this manual and its supplements are identified by the international hazard
symbols on the circuit diagram and parts list. Before replacing any of these components read the
parts list in this manual carefully. Substitute replacement components which do not have the same
safety characteristics as specified in the parts list may create X-ray radiation.
2. Do not slap or beat the cabinet or CRT, since this may result in fire or explosion.
3. Never allow the TV sharing a plug or socket with other large-power equipment. Doing so may result
in too large load, causing fire.
4. Do not allow anything to rest on or roll over the power cord. Protect the power cord from being
walked on, modified, cut or pinched, particularly at plugs.
5. Do not place any objects, especially heavy objects and lightings, on top of the TV set. Do not install
the TV near any heat sources such as radiators, heat registers, stove, or other apparatus that
produce heat.
6. Service personnel should observe the SAFETY INSTRUCTIONS in this manual during use and
servicing of this TV set. Otherwise, the resulted damage is not protected by the manufacturer.
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SERVICE MANUAL
SAFETY SYMBOL DESCRIPTION
The lightning symbol in the triangle tells you that the voltage inside this product may
be strong enough to cause an electric shock. Extreme caution should be exercised
when working on the TV with the back removed.
This is an international hazard symbol, telling you that the components identified by
the symbol have special safety-related characteristics.
FDA This symbol tells you that the critical components identified by the FDA marking have
special safety-related characteristics.
UL This symbol tells you that the critical components identified by the UL marking have
special safety-related characteristics.
C UL This symbol tells you that the critical components identified by the C-UL marking
have been evaluated to the UL and C-UL standards and have special safety-related
characteristics.
VDE
This symbol tells you that the critical components identified by the VDE marking have
special safety-related characteristics.
MAINTENANCE
1. Place the TV set on a stable stand or base that is of adequate size and strength to prevent it from
being accidentally tipped over, pushed off, or pulled off. Do not place the set near or over a
radiator or heat register, or where it is exposed to direct sunlight.
2. Do not install the TV set in a place exposed to rain, water, excessive dust, mechanical vibrations or
impacts.
3. Allow enough space (at least 10cm) between the TV and wall or enclosures for proper ventilation.
4. Slots and openings in the cabinet should never be blocked by clothes or other objects.
5. Please power off the TV set and disconnect it from the wall immediately if any abnormal condition
are met, such as bad smell, belching smoke, sparkling, abnormal sound, no picture/sound/raster.
Hold the plug firmly when disconnecting the power cord.
6. Unplug the TV set from the wall outlet before cleaning or polishing it. Use a dry soft cloth for
cleaning the exterior of the TV set or CRT screen. Do not use liquid cleaners or aerosol cleaners.
4

SERVICE MANUAL
ADJUSTMENTS
SET-UP ADJUSTMENTS
The following adjustments should be made when a complete realignment is required or a new picture
tube is installed.
Perform the adjustments in the following order:
1. Color purity
2. Convergence
3. White balance
Notes:
①The purity/convergence magnet assembly and rubber wedges need mechanical positioning.
②For some picture tubes, purity/ convergence adjustments are not required.
1. Color Purity Adjustment
Preparation:
Before starting this adjustment, adjust the vertical sync, horizontal sync, vertical amplitude and
focus.
1.1 Face the TV set north or south.
1.2 Connect the power plug into the wall outlet and turn on the main power switch of the TV set.
1.3 Operate the TV for at least 15 minutes.
1.4 Degauss the TV set using a specific degaussing coil.
1.5 Set the brightness and contrast to maximum.
1.6 Counter clockwise rotate the R /B low brightness potentiometers to the end and rotate the green
low brightness potentiometer to center.
1.7 Receive green raster pattern signals.
1.8 Loosen the clamp screw holding the deflection yoke assembly and slide it forward or backward to
display a vertical green zone on the screen. Rotate and spread the tabs of the purity magnet
around the neck of the CRT until the green zone is located vertically at the center of the screen.
1.9 Slowly move the deflection yoke assembly forward or backward until a uniform green screen is
obtained.
1.10 Tighten the clamp screw of the assembly temporarily. Check purity of the red raster and blue
raster until purities of the three rasters meet the requirement.
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SERVICE MANUAL
Yok
Fig. 1
2. Convergence Adjustment
Preparation:
Before attempting any convergence adjustment, the TV should be operated for at least 15 minutes.
2.1 Center convergence adjustment
2.1.1 Receive dot pattern.
2.1.2 Adjust the brightness/contrast controls to obtain a sharp picture.
2.1.3 Adjust two tabs of the 4-pole magnet to change the angle between them and red and blue
vertical lines are superimposed each other on the center of the screen.
2.1.4 Turn both tabs at the same time keeping the angle constant to superimpose red and blue
horizontal on the center of the screen.
2.1.5 Adjust two tabs of the 6-pole magnet to superimpose red/blue line and green line.
2.1.6 Remember red and blue movement. Repeat steps 2.1.3～2.1.5 until optimal convergence is
obtained.
2.2 Circumference convergence adjustment
2.2.1 Loosen the clamp screw holding the deflection yoke assembly and allow it tilting.
2.2.2 Temporarily put the first wedge between the picture tube and deflection yoke assembly. Move
front of the deflection yoke up or down to obtain better convergence in circumference. Push the
mounted wedge in to fix the yoke temporarily.
2.2.3 Put the second wedge into bottom.
2.2.4 Move front of the deflection yoke to the left or right to obtain better convergence in
circumference.
2.2.5 Fix the deflection yoke position and put the third wedge in either upper space. Fasten the
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SERVICE MANUAL
deflection yoke assembly on the picture tube.
2.2.6 Detach the temporarily mounted wedge and put it in either upper space. Fasten the deflection
yoke assembly on the picture tube.
2.2.7 After fastening the three wedges, recheck overall convergence and ensure to get optimal
convergence. Tighten the lamp screw holding the deflection yoke assembly.
Fig. 2
4-pole Magnet Movement 6-pole Magnet Movement
Center Convergence by Convergence Magnets
Incline the Yoke Up (or Down) Incline the Yoke Right (or Left)
Circumference Convergence by DEF Yoke
Fig.3
3. White Balance Adjustment
Generally, white balance adjustment is made with professional equipment. It’s not practical to get
good white balance only through manual adjustment. For TVs with I2C bus control, change the bus
data to adjust white balance.
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SERVICE MANUAL
CIRCUIT ADJUSTMENTS
Preparation:
Circuit adjustments should be made only after completion of set-up adjustments.
Circuit adjustments can be performed using the adjustable components inside the TV set. For TVs with
I2C bus control, first change the bus data.
1. Degaussing
A degaussing coil is built inside the TV set. Each time the TV is powered on, the degaussing coil
will automatically degauss the TV. If the TV is magnetized by external strong magnetic field,
causing color spot on the screen, use a specific degausser to demagnetize the TV in the following
ways. Otherwise, color distortion will be shown on the screen.
1.1 Power on the TV set and operate it for at least 15 minutes.
1.2 Receive red full-field pattern.
1.3 Power on the specific degausser and face it to the TV screen.
1.4 Turn on the degausser. Slowly move it around the screen and slowly take it away from the TV.
1.5 Repeat the above steps until the TV is degaussed completely.
2. Confirmation and Adjustment for Voltage
Caution: +B voltage has close relation to high voltage. To prevent X-ray radiation, set +B voltage to
the rated value.
2.1 Make sure that the supply voltage is within the range of the rated value.
2.2 Connect a digital voltmeter to the voltage output terminal of the main PCB. Power on the TV and
set the brightness and sub-brightness to minimum. Ensure that the voltage from the main PCB
reads as follows.
2.3 Regulate voltage adjustment components on the power section until the +B the voltage reaches the
rated value.
Table 2
Test Point Voltage (V)
Negative of VD851 118V±2V
Negative of VD852 17V±1V
Negative of VD854 11V±1V
Negative of VD857 14V +1V
-1.5V
Positive of C874 9V±0.5V
Positive of C878 5V±0.5V
Positive of C800 5V±0.25V
Note:
It’s impossible to check the power part separately from the main chassis board as the part is
mounted on the main chassis board. The power components, etc. should be checked for burnout
when power-on. If burned out, do not power on the TV again until the cause is found out.
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SERVICE MANUAL
3. High Voltage Inspection
Measure voltages of test points on the main PCB with the digital voltmeter. Measure the CRT high
voltage with the high-voltage testing equipment and heater voltage with the high-frequency
effective voltmeter. The rated values are shown as below.
Table 3
Test Point Voltage (V)
Negative of VD603 25±1.5V
27±1.5V (for BSC68V1 FBT only)
Negative of VD855A 190±5.0V
CRT anode 25±1.5KV
Heater 6.3±0.3Vrms
4. Focus Adjustment
Caution: Dangerously high voltages are present inside the TV. Extreme caution should be
exercised when working on the TV with the back removed.
4.1 After removing the back cover, look for the FBT on the main PCB. There should be a FCB on the
FBT.
4.2 Power on the TV and preheat it for 15 min.
4.3 Receive a normal TV signal. Rotate knob of the FCB until you get a sharp picture.
BeforeAdjusting AfterAdjusting
Fig. 4
5. Safety Inspection
5.1 Inspection for insulation and voltage-resistant
Perform safety test for all naked metal of the TV. Supply high voltage of 3000V AC, 50Hz (limit
current of 10mA) between all naked metal and cold ground. Test every point for 3 sec. and ensure
no arcing and sparking.
5.2 Requirements for insulation resistance
Measure resistance between naked metal of the TV and feed end of the power cord to be infinity
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SERVICE MANUAL
with a DC-500 high resistance meter and insulation resistance between the naked metal and
degaussing coil to be over 20MΩ.
6. SERVICE mode
6.1 To enter the DESIGN/SERVICE mode
Set the volume to 0. Then press and hold the MUTE button on the remote control, and press the
MENU button on the TV to enter the SERVICE mode. In this case, red “S”is displayed on the
upper center of the screen. To exit from the S mode, turn off the TV set by the POWER button on
the remote control.
Caution: The user service mode adjustment can be changed only when service personnel adjust
the whole set data during servicing. As the control data have dramatic effects on functions and
performance of the TV, service personnel should not tell user how to enter the SERVICE mode to
avoid improper data settings.
6.2 Adjustments and bus data (CH08T0606)
Table 4 Function Description for Bus Data
10
Bit Function Description Status
Bit7.6 Audio system options (available during
auto search and use of AUTO button)
00: B/G 01:I
10: D/K 11:M
Bit5
Bit4
SECAM
INHIBIT
00: SECAM gate pulse width, 2.2
usec
01: 2.0 usec
10: 1.8 usec
11: SECAM demodulation inhibit
Bit3 V MUTE When changing channels:
0:Y-MUTE 1:RGBMUTE
Bit2 SECAM 0:No 1:Yes
Bit1 AUTO2 0: PAL 1: Without PAL
MODE0
Bit0 Power-on modes 0: Memory on 1: Soft on
(
continued
)

SERVICE MANUAL
11
Bit7 Write-in LOGO 0:No 1:Yes
Bit6
Refresh AV terminals in main
cycle
0: Yes (Recommended) 1: No
Bit5 RFNTSCoptions 0:No 1:Yes
Bit4 Screen saver 0: No 1: Yes
Bit3 M 0:No 1:Yes
Bit2 D/K 0:No 1:Yes
Bit1 I 0:No 1:Yes
MODE1
Bit0 B/G 0:No 1:Yes
Bit7
With Channel Lock, horizontal
AFC is off?
0: Yes (Recommended) 1: No
Bit6 Mono system 1:Yes 0：No
Bit5 Single language 1:Yes 0：No
Bit4
TA1343 woofer or MDB output
mode options
0: Mono output 1: Overlapped to main
channel（Recommended）
Bit 3 Pull down sub menus? 1:Yes 0：No
Bit 2
Bit 1
MODE2
Bit.0
Auto language options
000 ENGLISH
0 0 1 FRENCH
010 GERMAN
011 RUSSIAN
100 INDONE
101 MALAY
110 FARSI
111 ARABIC
MODE3 BIT 7
Small character processor 1: Old 0: New
(Recommended)
(
continued
)

SERVICE MANUAL
(
continued
)
BIT 6
Waiting time when changing
channels with 0-9 buttons
1: Fast (1 sec.) 0: Slow (2 sec.)
(Recommended)
BIT 5 DVD option
1: No 0: Yes
(Recommended)
BIT.4
Step length setting for lighting up
gradually during power-on
1: Large step (Recommended) 0：Small
step
BIT 3
Numeral in Arabic indicated in
local language?
0:No 1: Yes
BIT 2 PWM output option 0: No 1: Yes
BIT 1 Instant on 1:Yes 0：No
BIT 0 AV Switch 4053 option 0:No 1:Yes
BIT 7
Audio processing IC (SOUND
menu) 0:No 1:Yes
BIT 6 Woofer option in SOUND menu 0:No 1:Yes
BIT 5 TA1343 option 0:No 1:Yes
BIT 4 No use 0:No 1:Yes
BIT 3 NJW1161 option (SRS IC) 0:No 1:Yes
BIT 2
NJW1160 option (BBE IC & SRS
IC) 0:No 1:Yes
BIT 1 NJW1137 option (BBE IC) 0:No 1:Yes
MODE4
BIT 0 Soft IIC option 0:No 1:Yes
Bit 7 No useOPT
Bit 6 VCO adjustments
0: PIF VCO functions (PIFVCO = 10) during
auto search and search；
1: PIFVCO = 10 during turn-on，and PIFVCO =
00 in Normal mode
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SERVICE MANUAL
Bit 5 No use
Bit 4 Large-amplitude AFT switch when no
signal
1:Off 0:On
Bit 3 Audio gain switch in MONO mode
0：927mVrms at 25kHz/dev
1：500mVrms at 25kHz/dev
Bit 2 Y-MUTE when changing channels 0: No 1: Yes
Bit 1
Turn-on logo display? (Logo
write-in function required)
1:Yes 0:No
Bit 0 No use
OSD Horizontal position of OSD
RCUT R cut off
GCUT G cut off
BCUT B cut off
GDRV G drive
BDRV B drive
CNTX Contrast Max.
BRTC Bright center
CNTC Contrast center
CNTN Contrast Min.
BRTX Bright Max.
BRTN Bright Min.
HPOS 50hz horizontal phase 00: -3usec 10: 01F: +3usec
VP50 V phase (50Hz) 0: V phase delay, 0H 7: 7H
HIT V size 00:-50% 20:0% 3F:50%
(continued)
13

SERVICE MANUAL
HPS Adjusting difference between horizontal centers in PAL and NTSC
VP60 V phase (60Hz) 0: V phase delay, 0H 7: 7H
HITS Adjusting difference between vertical amplitudes in PAL and NTSC
VLIN V-linearity 0:-15% 8: 0% F:15%
VSC V-S correction 0:-16% 8: 0% F:16%
VLIS Adjusting difference between vertical linear in PAL and NTSC
VSS Shift data of 50 Hz/ 60 Hz Correction
HIT69 Vertical amplitude in 16:9 mode (PAL)
HIT69S Vertical amplitude in 16:9 mode (NTSC)
V01 Volume output data at 1%
V25 Volume output data at 25%
V50 Volume output data at 50%
V100 Volume output data at 100%
Bit 3.2 VCD standby
00: Normal 01: Normal
10: Normal 11: VCD standby
STBY
Bit 1.0 IF standby
00: Normal 01: Normal
10: Normal 11: IF standby
VCEN Vertical centering 00: -32% 20: 0% 3F: 30%
Bit7 Arabic 1:Yes 0:No
Bit6 Farsi 1:Yes 0:No
Bit5 Malay 1:Yes 0:No
Bit 4 Indonesian 1: Yes 0: No
Bit3 Russian 1:Yes 0:No
Bit2 German 1:Yes 0:No
Bit1 French 1:Yes 0:No
LANG
BIT0 English 1:Yes 0:No
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SERVICE MANUAL
15
Table 5 Bus Data
Item Data Item Data Item Data Item Data
*MODE0 84 SCNT 09 HPOS 11 BSNS 00
*MODE1 1F CNTC 40 VP50 01 MOD 40
*MODE2 1BCNTN 08HIT 18 STBY 00
*MODE3 18 BRTX 19HPS 04 SVM 00
*MODE4 60 BRTN 20 VP60 02 VBLK 00
*LANG FF COLX 35 HITS 01 UCOM 00
NOT MENU 9E COLN 00 VLIN 05 VTST 00
MEUN ICON FB TNTX 28 VSC 00 PYNX 26
MAIN MEUN 91 TNTN 28 VLIS 00 PYNN 1B
MEUN CHAR 07 ST3 25 VSS 00 PYXS 22
MEUN CHAR
HIGH 02 SV3 30 VCEN 16 PYNS 1E
BBE 9C ST4 20 HIT69 14 BASC 40
OSDF 64 SV4 30 HIT69S 01 BASX 70
OSD 20 SVD 30 SBY 05 TREC 40
*OPT 60 ASSH 07 SRY 09 BALC 40
RCUT 40 SHPX 3F BRTS 00 BAS1 64
GCUT 20 SHPN 20 RAGC 20 BAS2 20
BCUT 20 TXCX 3F HAFC 09 BAS3 50
GDRV 40 RGCN 1F *V01 15 TRE1 64
BDRV 40 ABL 2C *V25 4D TRE2 20
CNTX 7F DCBS 13 *V50 65 TRE3 50
BRTC 40 CLTO 26 *V100 7F TA1343-06 6C
COLC 40 CLTM 22 WOOFER 40 NO USE 00
TNTC 48 CLTS 20 STAT 00 NO USE 64
TNTCAV 48 CLVO 24 FLG0 06 WON1 01
COLP F8 CLVD 20 FLG1 08 WON2 00
COLS 40 DEF 01 REFP 00 NOIS 01
DCOL 20 AKB 00 RSNS 00 VATT 70
SCOL 07 SECD 18 GSNS 00
Notes:
The data sheet may differ dependent on different models.
The data sheet may differ dependent on different CRTs for the same model.
Refer to table 4 set the data marked with “*” defending on functions of TVs.

SERVICE MANUAL
STRUCTURE AND CHASSIS FUNCTION DESCRIPTION
1. STRUCTURE BLOCK DIAGRAM
16
Tuner
U101
FBT
T402
Horizontal
Output
V405
IF Pro-amp.
+S AW F
Rem ote control
TDA8 9 4 4 AJ
N301
R
L
Video
Am plifier
V901-V903
Vertical Out
LA78040
N602
Line Drive
V404 T401
2INI IC
TMPA8801PSBNG
N201
AV Switch
HEF4053BP
N
3
50
Rem ote
Sensor
HS0038
EEPROM
AT24C16
D702
Circui for
Buttons On
The TV
A in
L
H
Y
Cb
Cr
I2C
R G B
CRT
S-Terminal
TV Audio
ABL
HV
SV
FV
V in
STR-G5653
Power Circuit
N801
220V
50Hz
9V-2
12V
17V
5V-1
120V
9V
5V-2
V out
I2C
TA1343N
N302
A out

SERVICE MANUAL
2. BLOCK DIAGRAM FOR SUPPLY VOLTAGE SYSTEM
.
17
Degaussing
Circuit
RT801XT801
Switch
Regulator
N801 T801etc.
SamplingAmplifier
VD820
V/R/L
Output Contr ol
V501-V503
AV Switch
Vertical
Output
N601
2in1IC
N201
Regulator
V881 VD883
C80
Line Drive
V431
EEPROM
D702 2 in 1 IC
N201
Band Contr ol
V230 V231
Sound Powe r
Amplifier
N301
Video
Amplifier
V901-V903
SecondSound
Trap
V204V207
Hz Bridge
Rectifier
VD801-VD804
C803-C806
Filter
L803C807
9V-2
5V-2
17V
5V-1
118V
33V
27V
190V
IF Pre-
amplifier
V101
2 in 1 IC
N201
Regulator
V883 VD887
C874
Regulator
N802 C878
Regulator
N121 R128
C125 C126
U101
Tuner
HV FV SV
Horizontal
Output
V432
FBT
T402
Vertical
Output
N601
5V-2
5V-2
LED RMT
Circuit
N701 D701
Interference-
proofCircuit
L802C801C802
N350
12V
17V
220V
50Hz
TA1343N
N302

SERVICE MANUAL
18
3. CHASSIS DESCRIPTION
General Description
CN-18EA(V2) chassis is applied in 21BM91 series.By use of Toshiba V/C/D-MCU 2IN1 IC for TV
small signal processing and bus control, the chassis enables TV tuning, adjustment, control and
picture correction, featuring high-integration, high-performance-to-price ratio and high-
reliability and compact circuit with fewer externalcomponents. The chassis, widely
used in small and medium TVs, providesmuch more convenience for manufacturing and technical
service. It includes:
 2IN1 IC TMAP8801PSBNG for PAL/NTSC/SECAM small signal processing and bus control
 EEPROM AT24C16 for data memory
 LA78040 for vertical output power amplifying
 TA1343N for audio processor
 TDA8944J for audio power amplifying
 Thick-film IC STR-G5653 for power circuit adjustment and control
The following features are available in the chassis:
 Color systems: PAL, NTSC, SECAM
 Sound systems: D/K B/G I M
 236 programs preset
 AV stereo/Surround/Woofer
 I2C bus control
 Electronic program table
 Intelligent lock
 Biorhythm
 Calendar inquiry
The chassis mainly uses the following ICs and assemblies.
Table 6 Key ICs and Assemblies
Serial
No. Position Type Description
1 D702 AT24C16 EERPOM
2 N201 CH08T0606
(TMPA8801PSBNG) 2IN1 IC (Small signal processor + micro control unit (MCU))
3 N301 TDA8943SF/TDA8944AJ Audio power amplifier
4 N302 TA1343N Audio processor
5 N602 LA78040 Vertical scan output stage circuit
6 N801 STR-G5653 Switch-mode power supply control
7 N350 HEF4053BP AV/TV Switch
8 U101 TDQ-5B6M Tuner