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COLOUR TV SET
Models:
25CT23FSR
29CT23FSR
SERVICE MANUAL
www.akai.ru
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SERVICE MANUAL
TABLE OF CONTENTS
TABLE OF CONTENTS................................................................................................... 1
SAFETY INSTRUCTIONS AND MAINTENANCE......................................... 2
X-RAY RADIATION PRECAUTION.......................................................................................... 2
SAFETY PRECAUTION.............................................................................................................. 2
PRODUCT SAFETY NOTICE .................................................................................................... 3
SAFETY SYMBOL DESCRIPTION........................................................................................... 3
MAINTENANCE............................................................................................................................ 4
ADJUSTMENTS .................................................................................................................. 5
SET-UP ADJUSTMENTS ........................................................................................................... 5
CIRCUIT ADJUSTMENTS.......................................................................................................... 8
STRUCTURE AND CHASSIS FUNCTION DESCRIPTION..................... 14
STRUCTURE BLOCK DIAGRAM ............................................................................................. 14
BLOCK DIAGRAM FOR SUPPLY VOLTAGE SYSTEM ...................................................... 15
CHASSIS DESCRIPTION ...........................................................................................................16
SERVICE DATA ..................................................................................................................17
TECHNICAL DATA OF KEY ICS ...............................................................................................17
WAVEFORMS OF KEY POINTS ...............................................................................................35
SERVICE DATA OF KEY ICS ....................................................................................................38
REPLACEMENT OF PARTS .......................................................................................44
APPENDIX
1. CIRCUIT DIAGRAM
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INSTRUCTIONS FOR SERVICE SAFETY 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
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.
identical to the original fitted as specified in the parts list.
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.
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.
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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.
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
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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.
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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:
The purity/convergence magnet assembly and rubber wedges need mechanical
positioning. Refer to Fig1, 2.
For 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.
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.
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Yok
Fig. 1
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
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.
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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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
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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
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with I
C 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 Power on the TV and receive Philips test pattern.
2.2 Check the resistors and coils for being burned. (If the fuse is burned out, do not power on the
TV again until the cause is found out.)
2.3 Measure voltages of test points 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 table 2.
Table 2
Test Point Voltage (V)
Negative of VD831 145 1.5V
Negative of VD461B 12 1V
Negative of VD832 15 1V
Positive of C462 17 1V
Positive of C452 47 3V
Positive of C492 195 5V
Heater 6.3 0.3Vrms
CRT 28.8KV 1KV
3. High Voltage Inspection
Caution: No high voltage adjustment components inside the chassis. Please perform
high voltage inspection in the following ways.
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3.1 Connect a precise static high voltmeter to the second anode (inside the high voltage cap) of the
CRT.
3.2 Plug in the supply socket (150-250V ~, 50Hz) and turn on the TV. Set the brightness and
contrast to minimum (0 A).
3.3 The high voltage reading should be less than the limited EHT voltage.
3.4 Change the brightness from minimum to maximum, and ensure high voltage not beyond the
limitation in any case.
Nominal EHT voltage: 28.8KV 1KV Limited EHT voltage: 32KV
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.
Before Adjusting After Adjusting
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, 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 with a DC-500 high resistance meter and insulation resistance between the naked metal
and degaussing coil to be over 20M .
6. SERVICE mode
6.1 To enter the SERVICE mode
Set the volume to 0 by the remote control. Then press and hold the MUTE button on the
remote control and MENU button on the TV at the same time for over 2 seconds. In the S mode,
press the POWER button to quit the S mode.
S
( S is red and other items are yellow.)
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Use the / buttons on the remote control to highlight an adjustment and the / buttons
to adjust it.
The POS+/-, / / / ,1~6, RECALL, VOL+/-, MUTE and POWER buttons on the remote
control function in the S mode, but 100+, 7, 8, 9 and 0 buttons not.
6.2
Bus data
Table 3 Bus data
Data in S
Mode
OP1 7B Option set byte 1 See Table 4
OP2 48 Option set byte 2 See Table 4
OP3 FF Option set byte 3 See Table 4
OP4 F5 Option set byte 4 See Table 4
OP5 36 Option set byte 5 See Table 4
OP6 28 Option set byte 6 See Table 4
AVG Vertical output
INIT Initializing E2PROM
TAB Data check sheet See Table 5
VX00 19 4:3
VX50 01 16:9
VX99 38 Zoom
VS Set to the optimum Half vertical output
VA Set to the optimum
SC Set to the optimum S correction
VSH Set to the optimum
5OV Set to the optimum
HP Set to the optimum Parallelogram correction
HB Set to the optimum Bow correction
5HS Set to the optimum
5HA Set to the optimum
Adjustment Description
Vertical amplitude (When vertical frequency is identified to
50Hz, “5VA” is displayed when identified to 60Hz, “6VA”
displayed.)
Vertical shift (When vertical frequency is identified to 50Hz,
“5VSH” is displayed when identified to 60Hz, “6VSH”
displayed.)
Character field starting position (When vertical frequency is
identified to 50Hz, “5OV” is displayed when identified to
60Hz, “6OV” displayed.)
Horizontal shift (When vertical frequency is identified to
50Hz, “5HS” is displayed when identified to 60Hz, “6HS”
displayed.)
Horizontal amplitude (When vertical frequency is identified to
50Hz, “5HA” is displayed when identified to 60Hz, “6HA”
displayed.)
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East-west pincushion correction (When vertical frequency is
5EW Set to the optimum
UCP Set to the optimum Upper corner correction
BCP Set to the optimum Bottom corner correction
TC Set to the optimum Trapezoidal correction
RCUT Set to the optimum Red gun cutoff voltage
GCUT Set to the optimum Green gun cutoff voltage
RDRV Set to the optimum Red gun drive voltage
GDRV Set to the optimum Green gun drive voltage
BDRV 20 Blue gun drive voltage
YDFP 0D Brightness delay PAL
YDFN 0D Brightness delay NTSC
YDFS 0D Brightness delay SECAM
YDAV 0D AV brightness delay
AGC Set to the optimum Automatic gain control (AGC)
VOL 28 Volume initial value
IFFS O3 Intermediate frequency
CL OB
AGCS 03 AGC speed
VG2B 30 VG2 brightness
SVOL 36 Volume 00
MVOL 3C Volume 25
SBRI 1F Sub brightness
MBRI 33 Brightness Max.
SCON 0C Sub contrast
MCON 3F Contrast Max.
MCOL 3F Color Max.
identified to 50Hz, “5EW” is displayed when identified to
60Hz, “6EW” displayed.)
OP1
Table 4 Option bit setting
Bit Item Description
0 OP_HOTEL Hotel Mode: 1: Yes, 0: No
1 OP_HWSN Audio processor: 1: TDA9859, 0: No
2 OP_SUPERWOOFER Super woofer: 1: Yes, 0: No
3 OP_NTSC NTSC option: 1: Yes, 0: No
4 OP_AV2 1: With AV2; 0: Without AV2
5 OP_SVHS S-Video: 1: Yes, 0: No
6 OP_DVD DVD 1: Yes, 0: No
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7 OP_RGB RGB 1: Yes, 0: No
0 OP_AVL AVL 1: Yes, 0: No
OP2
OP3
1 OP_AUTO_SOUND
2 OP_KEY
3 OP_OSO Switch off in vertical overscan
4 OP_NOT_3 National option (disabled)
5 OP_USER_LOGO User write-in logo option (prior to Changhong logo)
6 OP_ON_BACK Power-on auto-test background: 1: Blue, 0: Black
7 OP_FSL Slicing level for vertical sync
0 OP_ENGLISH English
1 OP_FARSI Farsi
2 OP_ARABIC Arabic
3 OP_RUSSIAN Russian
4 OP_FRENCH French
5 OP_GERMAN German
6 OP_ITALY Italian
uto sound system test: 1:Yes, 0: No
Key: 1: Standard 0: Non-standard
OP4
OP5
7 OP_SPAIN Spanish
Window selection of sound PLL:
0 OP_FMWS
1: Large window, 0: Small window
OP_DIRECT_SWITCH_ONMemory on: 1: Remote on if remote off; instant on if
1
AC off 0: Soft on
2 OP_HCO EHT: EW control 1:On 0: Off
Changhong logo display
3 OP_CHH_LOGO
1: Yes under no signal condition 0: No
4 OP_SOUND_DK Audio system DK option: 1: Yes, 0: No
5 OP_SOUND_BG Audio system BG option: 1: Yes, 0: No
6 OP_SOUND_I Audio system I option: 1: Yes, 0: No
7 OP_SOUND_M Audio system M option: 1: Yes, 0: No
0 OP_TUNER Tuner 1: Philips tuner, 0: Panasonic tuner
1 OP_AUTO_LANG0
Auto language option: English - Farsi - Arabic -
2 OP_AUTO_LANG1
Russian - French - German - Italian – Spanish, for
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example:
OP6
3 OP_AUTO_LANG2
4 OP_FORF
5 OP_FORS
6 OP_AV_ON
7 OP_HOTEL_ON_PROG
0 OP_AUTOTEST Power-on auto test: 1: Yes, 0: No
1 OP_PSNS Sensitivity
2 OP_BSCREEN Black screen when changing channels 1: Yes 0: No
3 OP_SECAM SECAM option: 1: Yes, 0: No
4 OP_DFL Disable flash protection
LANG2 /LANG1/ LANG0
0/0/0”: English, “0/0/1”: Farsi
Vertical frequency (OP_FORS/FORF): 00-Auto (60Hz
under no signal condition), 01-KeepLast,
10-Force60Hz, 11-Auto (50Hz under no signal
condition)
1: The former mode before power-off when power-on
0: TV mode when power-on
Fixed to Channel 1 when power-on Activated with
OP-HOTEL 1: Yes, 0: No
Notes:
5 OP_SIF SIF selection 1: External, 0: Internal
6 OP_EXT_SIF0
7 OP_EXT_SIF1
Table 5 TAB data check sheet
OP1 OP2 OP3 OP4 OP5 OP6
VX00 YD( FP/FN/FS/ AV) AGC I FFS CL AGCS
VOL VG2B SVOL MVOL
SBRI MBRI SCON MCON MCOL
RCUT GCUT RDRV GDRV BDRV
The data sheet may differ dependent on different models.
The data sheet may differ dependent on different CRTs for the same model.
External circuit sound system selection (SIF1/SIF0)
00: DK, 01: BG, 10: I, 11: M
Activated with OP-SIF
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