LG CF28A64D Service Manual

ADJUSTMENT INSTRUCTIONS

*Safety Precautions

1. It is safe to adjust after using insulating transformer between the power supply line and chassis input to prevent the risk of electric shock and protect the instrument.

2. Never disconnect leads while the TV receiver is on.

3. Don't short any portion of circuits while power is on.

4. The adjustment must be done by the correct appliances. But this is changeable in view of productivity.

5. Unless otherwise noted, set the line voltage to 230Vac

+_10%, 50Hz.

* Test Equipment required

1. RF signal generator (with pattern generator)

2. DC Power Supply

3. Multimeter (volt meter)

4. Oscilloscope

5. Color analyzer

Main Board(Component side view)

MAIN BOARD

38.9MHz 10mVp-p

RF SIGNAL GENERATOR

5 0.1Vdc DC POWER SUPPLY

VL102

4.5M

CERAMIC CAP. 10000pF

TUNER

TP5

J156

AGC

VL101

PIF

TDA9811

17 16

TP1

IC101

TP3

30 32

Z102

CERAMIC CAP. 10000pF

VR101

VR102

ADJ.

AGC ADJ.

(TP point is on the copper side of PCB)

TP1 : pin23 of IC101 TP2 : pin9 of IC101 TP3 : pin30 of IC101 TP5 : J156

TP2

MULTIMETER

Frequency

38.9MHz

Modulation

OFF

Output level

10mVp-p

(Table 1)

* SECAM L' Adjustment

NOTE :This adjustment should be performed after PIF

adjustment.

Test Point : TP1

Adjust : VR101

1) Tune the TV set to receive a SECAM-L' signal.

2) Adjust VR101 so that the DC voltage may be indicated

+_0.1Vdc.

2.6

* SECAM L/L' sound Adjustment

Test Point : C638(Refer to the Fig.2)

Adjust : VL102

GND

MSP3410

AM INPUT

IC601

OSCILLOSCOPE

C638

J116

Fig. 2

Noise Level

Fig. 1 : Connection Diagram of Equipment for PIF Adjustment

* PIF (Picture Intermediate Frequency) Adjustment

Test Point : TP1

Adjust : VL101

1) Connect the measuring equipment to the Main Board as shown in Fig.1.

2) Set RF frequency and output level of RF SIGNAL GENERATOR as shown Table 1.

3) Turn on DC power supply.

4) Adjust VL101 so that the DC voltage may be indicated

+_0.1Vdc.

2.6

(Before Adjustment) (After Adjustment)

1) Connect the Oscilloscope to the Main Board as shown in Fig. 2.

2) Set pattern generator as shown Table 2.

3) Adjust VL102 so that the Noise level is minimized.

System

SECAM-L

Signal Pattern

Color bar

Sound signal

Off

Carrier signal

(Table 2)

* Vertical/Horizontal/E-W (East-West)

Adjustment (LINE SVC 1)

NOTE : These adjustments are already aligned at

the time of manufacture for optimum performance. Readjustment of them should not be necessary unless IC02 (EEPROM) is defective. Because all the information of these adjustment are memorized in that IC.

Adjustment Procedures

1) Tune the TV set to receive a digital circle pattern unless otherwise noted.

2) Press OKbutton on Control Board continuously and OK button on remote controller then you can find On Screen Display. (Refer to the following Fig.3).

3)Press PR+ or PR- button for desirous function adjustment.

4) Press VOL+ or VOL- button for correct picture.

5) Press OK button to memorize all the adjusted data.

6) After finishing adjustment, press TV/AV button on remote controller then TV is changed from SVC mode to normal mode.

[LINE SVC1] 1

VL 43EW 37 VA 21 EP 39 SC 35EC 29 VS 35ET 20 HS 31 50HZ*

CH5

EW--(Horizontal Width)

Adjust to that a digital circle pattern looks like exact circle.

EP--(East-west Parabola)

Adjust so that middle portion of the outermost left and right vertical line looks like parallel with vertical lines of the CPT.

EC--(East-west Corner)

Adjust so that the vertical line at every 4 corners of the screen looks like parallel with the vertical lines of the CPT.

ET--(East-west Trapezium)

Adjust to make the length of top horizontal line same with it of the bottom horizontal line.

* White Balance Adjustment.(LINESVC 2)

NOTE :This adjustment should be performed after screen

voltage adjustment.

1) Tune the TV set to receive an 100% white pattern.

2) Press Number 2 button on remote controller in the SVC Mode (press OK button on control board continuously and OK button on remote controller) then you can find On Screen Display. (Refer to the following Fig.4).

3) Press PSM (RED) button on remote controller. (Standard picture)

4)Press PR+ or PR- button for desirous function adjustment.

5) Adjust VOL+ or VOL- button for GG31. Adjust VOL+ or VOL-button in each status of "RG--"/"BG--"

for X=288

temperature 9000

+_8, Y=295+_8 with color analyzer (color

K).

*: This is only displayed according to

receiving system. PAL/SECAM System : 50Hz

[

NTSC System : 60Hz

Fig. 3

VL--(Vertical Linearity)

Adjust so that the boundary line between upper and lower half is in accord with geometric horizontal center of the CPT.

VA--(Vertical Amplitude)

Adjust so that the circle of a digital circle pattern may be located within the effective screen of the CPT.

SC--(Vertical "S" correction)

Adjust so that all distance between each horizontal lines are to be the same.

VS--(Vertical Shift)

Adjust so that the horizontal center line of a digital circle pattern is in accord with geometric horizontal center of the CPT.

HS--(Horizontal Shift)

Adjust so that the vertical center line of a digital circle pattern isinaccordwithgeometricverticalcenteroftheCPT

[LINE SVC2] 1

RG31 GG31 BG23 DY12*

CH5

Fig. 4

* : Never change this data, this is an important

reference data for TV.

Ref) PAL I/I': DY15

NOTE :If press Number 3 button on the remote controller

in the SVC mode then you can find On Screen Display. (Refer to the following Fig.5).

[LINE SVC3] 1

FP 30 NP 110 SP 23 SV 75

CH5

Fig. 5

*Never change these data, these are important

referencedataforTV

PURITY & CONVERGENCE ADJUSTMENT

Caution:

Convergence and Purity have been factory aligned. Do not attempt to tamper with these alignments. However, the effects of adjacent receiver components, or replacement of picture tube or deflection yoke may require the need to readjust purity any convergence.

DEFLECTION YOKE

PURITY &CONVERGENCE MAGNET ASSEMBLY

6-POLE

,,,

RUBBER WEDGES

,,,

PURITY MAGNET

4-POLE

GLASS CLOTH TAPE

X-AXIS YOKE POSITIONING (L/R PURITY)

5.Reconnect the internal degaussing coil.

6. Position the beam bender locking rings at the 9 o'clock position and the other three pairs of tabs (2,4 and 6 pole magnets) at the 12 o'clock position.

6-POLE

MAGNETS

4-POLE MAGNET

MAGNES

CONVERGENCE MAGNET ASSEMBLY

PURITY MAGNET(2-POLE)

* Purity Adjustment

This procedure DOES NOT apply to bonded yoke and picture tube assemblies. The instrument should be at room temperature (60 degrees F or above) for six (6) hours and be operating at low beam current (dark background) for approximately 20 to 30 minutes before performing purity adjustments.

CAUTION:Do not remove any trim magnets that may be

attached to the bell of the picture tube.

1. Remove the AC power and disconnect the internal degaussing coil.

2. Remove the yoke from the neck of the picture tube.

3. If the yoke has the tape version beam bender, remove it and replace it with a adjustable type beam bender (follow the instructions provided with the new beam bender)

4. Replace the yoke on the picture tube neck, temporarily remove the three (3) rubber wedges from the bell of the picture tube and then slide the yoke completely forward.

7. Perform the following steps, in the order given, to prepare the receiver for the purity adjustment procedure.

a. Face the receiver in the "magnetic north" direction.

b. Externally degauss the receiver screen with the television

power turned off.

c. Turn the television on for approximately 10 seconds to

perform internal degaussing and then turn the TV off.

d. Unplug the internal degaussing coil. This allows the

thermistor to cool down while you are performing the purity adjustment. DO NOT MOVE THE RECEIVER FROM ITS "MAGNETIC NORTH" POSITION.

e. Turn the receiver on and obtain a red raster by increasing

the red bias control (CW) and decreasing the bias controls for the remaining two colors (CCW).

f. Attach two round magnets on the picture tube screen at 3

o'clock and 9 o'clock positions, approximately one (1) inch from the edge of the mask (use double-sided tape).

3-2

1.ADJUST YOKE Z-AXIS FIRST TO GET EQUAL BLUE COLOR CIRCLES

MAGNETS

RED RED

2 .ADJUST BEAM BENDER 2 POLE MAGNET TO GET FOUR EQUAL COLOR CIRCLES

8. Referring to above, perform the following two steps: a. Adjust the yoke Z-axis to obtain equal blue circles. b. Adjust the appropriate beam bender tabs to obtain correct

purity (four equal circles).

9. After correct purity is set, tighten the yoke clamp screw and

remove the two screen magnets.

10.Remove the AC power and rotate the receiver 180 degrees

(facing "magnetic south").

11. Reconnect the internal degaussing coil.

12. Turn the receiver on for 10 seconds (make sure the receiver

came on) to perform internal degaussing, and then turn the receiver off.

13. Unplug the internal degaussing coil.

14. Turn on the receiver and check the purity by holding one (1)

round magnet at the 3 o'clock and a second round magnet at 9 o'clock position. If purity is not satisfactory, repeat steps 8 through 14.

15. Turn off the receiver and reconnect the internal degaussing

coil.

* Convergence Adjustment

Caution:This procedure DOES NOT apply to bonded yoke and

picture tube assemblies. Do not use screen magnets during this adjustment procedure. Use of screen magnets will cause an incorrect display.

1. Remove AC power and disconnect the internal degaussing

coil.

2. Apply AC Power and set the brightness to the Picture Reset

condition. Set the Color control to minimum.

3. Apply 8V to the pin.

6. Reconnect the internal degaussing coil and apply AC power.

7. Turn the receiver on for 10 seconds to perform internal degaussing and then turn the receiver off again.

8. Unplug the internal degaussing-coil.

9. Turn on the receiver, connect a signal generator to the VHF antenna terminal and apply a crosshatch signal.

Caution:During the convergence adjustment procedure, be

very careful not to disturb the purity adjustment tabs are accidentally move, purity should be confirmed before proceeding with the convergence adjustments.

Note:

Make sure the focus is set correctly on this instrument

before proceeding with the following adjustment.

10. Converge the red and blue vertical lines to the green vertical line at the center of the screen by performing the following steps (below TABLE). a. Carefully rotate both tabs of the 4-pole ring magnet

simultaneously in opposite directions from the 12 o'clock position to converge the red and blue vertical lines.

b. Carefully rotate both tabs of the 6-pole ring magnet

simultaneously in opposite directions form the 12 o'clock position to converge the red and blue (now purple) vertical lines with the green vertical line.

11. Converge the red and blue horizontal with the green line at the center of the screen by performing the following steps. (below TABLE)

a. Carefully rotate both tabs of the 4-pole ring magnet

simultaneously in the same direction (keep the spacing between the two tabs the same) to converge the red and blue horizontal lines.

b. Carefully rotate both tabs of the 6-pole ring magnet

simultaneously in same direction (keep the spacing between the two tabs the same) to converge the red and blue (now purple) horizontal lines with the green horizontal line.

c. Secure the tabs previsouly adjusted by locking them in

place with the locking tabs on the beam bender.

4. Adjust the Red, Green and Blue Bias controls to get a dim white line.

5. Remove the AC power and 8V from the pin.

3-3

3-4

RING PAIRS

POLE

ROTATION DIRECTION

OF BOTH TABS

OPPOSITE

SAME

OPPOSITE

SAME

MOVEMENT OF RED

AND BLUE BEAMS

B B

B R B R

B R

POLE

12. While watching the 6 o'clock positions on the screen, rock the front of the yoke in a vertical (up/down) direction to converge the red and blue vertical lines. (Fig upper left)

13. Temporarily place a rubber wedge at the 12 o'clock position to hold the vertical position or the yoke.

14.

Check the 3 o'clock and 9 o'clock areas to confirm that the red and blue horizontal lines are converged. If the lines are not converged, slightly offset the vertical tilt of the yoke (move the rubber wedge if necessary) to equally balance the convergence error of the horizontal lines at 3 o'clock and 9 o'clock and the vertical lines at 6 o'clock and 12 o'clock.

15. Place a 1.5 inch piece of glass tape over the rubber foot at the rear of the 12 o'clock wedge.

16. While watching the 6 o'clock and 12 o'clock areas of the screen, rock the front of the yoke in the horizontal (left to right) motion to converge the red and blue horizontal lines. (Fig. upper right)

17. Temporarily place a rubber wedge at the 5 o'clock and 7 o'clock positions to hold the horizontal position of the yoke.

18. Check the 3 o'clock and 9 o'clock areas to confirm that the red and blue vertical lines are converged. If the lines are not converged, slightly offset the horizontal tilt of the yoke (move the temporary rubber wedges if necessary) to equally balance the convergence error of the horizontal lines at 6 o'clock and 12 o'clock and the vertical lines at 3 o'clock and 9 o'clock.

19. Using a round magnet confirm purity at the center, right and left sides and corners. See Purity Adjustment Procedure.

20. Reconfirm convergence and apply a 1.5 inch piece of glass tape over the rubber foot at the rear of the 5 o'clock and the 7 o'clock wedges.

RED

BLUE

RED BLUE

BLUE

RED

GREEN

BLUE RED

GREEN

ADJUSTMENT

VIEWING

AREA

UP/DOWN ROCKING OF THE YOKE CAUSES OPPOSITE ROTATION OF RED AND BLUE RASTERS

ADJUSTMENT

VIEWING

AREA

RED

GREEN

TV SCREEN

LEET/RIGHT ROCKING OF THE YOKE CAUSES OPPOSITE SIZE CHANGE OF THE RED AND BLUE RASTERS

UP/DOWN ROCKING OF THE YOKE CAUSES OPPOSITE ROTATION OF RED AND BLUE RASTERS

LEFT/RIGHT ROCKING OF THE YOKE CAUSES OPPOSITE SIZE CHANGE OF THE RED AND BLUE RASTERS

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