SITRONICS 25F83 Manuale utente

FILENO.SM-CTV-098

COLOR TELEVISION

MODEL NO. 25F83/PF25F83/PF29F83

CHASSIS NO. CH-16(S)

Please read this manual carefully before service.

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. Refer to Fig1, 2.

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.

1.10Tighten 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.

SERVICE MANUAL

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.

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

SERVICE MANUAL

Center Convergence by Convergence Magnets

Incline the Yoke Up (or Down) Incline the Yoke Right (or Left)

the bus data to adjust white balance.

Fig. 2

4-pole Magnet Movement 6-pole Magnet Movement

Circumference Convergence by DEF Yoke

Fig.3

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 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 anode voltages 25KV±1KV (for 25" pure flat CRT only)

29KV±1KV (for 25" super pure flat CRT only)

28.8KV±1KV (for 29” CRT only)

SERVICE MANUAL

3. High Voltage Inspection

Caution: No high voltage adjustment components inside the chassis. Please perform

high voltage inspection in the following ways.

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 (0μA).

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 Limited EHT voltage Remarks

25KV±1KV 30KV for25"pureflatCRTonly

29KV±1KV 32KV for 25" super pure flat CRT only

28.8KV±1KV 32KV for29”CRTonly

Note: The data sheet may differ dependent on different CRTs.

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, 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 20MΩ.

SERVICE MANUAL

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”is red and other items are yellow.)

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 Adjustment Description

OP1 7B Option set byte 1（See Table 4）

OP2 4C 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 Vertical amplitude (When vertical frequency is identified to

50Hz, “5VA” is displayed；when identified to 60Hz, “6VA”

displayed.)

( continued )

SERVICE MANUAL

SC Set to the optimum S correction

VSH Set to the optimum Vertical shift (When vertical frequency is identified to 50Hz,

“5VSH” is displayed；when identified to 60Hz, “6VSH”

displayed.)

5OV Set to the optimum Character field starting position (When vertical frequency is

identified to 50Hz, “5OV” is displayed；when identified to

60Hz, “6OV” displayed.)

HP Set to the optimum Parallelogram correction

HB Set to the optimum Bow correction

5HS Set to the optimum Horizontal shift (When vertical frequency is identified to

50Hz, “5HS” is displayed；when identified to 60Hz, “6HS”

displayed.)

5HA Set to the optimum Horizontal amplitude (When vertical frequency is identified to

50Hz, “5HA” is displayed；when identified to 60Hz, “6HA”

displayed.)

5EW Set to the optimum East-west pincushion correction (When vertical frequency is

identified to 50Hz, “5EW” is displayed；when identified to

60Hz, “6EW” displayed.)

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.

( continued )

SERVICE MANUAL

SCON 0C Sub contrast

MCON 3F Contrast Max.

MCOL 3F Color Max.

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

OP1

7 OP_RGB RGB 1: Yes, 0: No

0 OP_AVL AVL 1: Yes, 0: No

1 OP_AUTO_SOUND

uto sound system test: 1:Yes, 0: No

2 OP_KEY Key: 1: Standard，0: Non-standard

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

OP2

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

OP3

7 OP_SPAIN Spanish

OP4 0 OP_FMWS Window selection of sound PLL:

1: Large window, 0: Small window

( continued )

SERVICE MANUAL

1 OP_DIRECT_SWITCH_

Memory on: 1: Remote on if remote off; instant on if

AC off 0: Soft on

2 OP_HCO EHT: EW control 1:On 0: Off

3 OP_CHH_LOGO Changhong logo display

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

2 OP_AUTO_LANG1

3 OP_AUTO_LANG2

Auto language option: English - Farsi - Arabic -

Russian - French - German - Italian – Spanish, for

example:

LANG2 /LANG1/ LANG0：

“0/0/0”: English, “0/0/1”: Farsi

4 OP_FORF

5 OP_FORS

Vertical frequency (OP_FORS/FORF): 00-Auto (60Hz

under no signal condition), 01-KeepLast,

10-Force60Hz, 11-Auto (50Hz under no signal

condition)

6 OP_AV_ON 1: The former mode before power-off when power-on

0: TV mode when power-on

OP5

7 OP_HOTEL_ON_PROG Fixed to Channel 1 when power-on （Activated with

OP-HOTEL）1: Yes, 0: No

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

5 OP_SIF SIF selection 1: External, 0: Internal

6 OP_EXT_SIF0

OP6

7 OP_EXT_SIF1

External circuit sound system selection (SIF1/SIF0)

00: DK, 01: BG, 10: I, 11: M

（Activated with OP-SIF）

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