LG PC63A Schematic

Preparation for VCO Adjustment

1. Connect the measuring equipment to the TV as shown in Fig. 1.

2. Set RF output level of sweep S.G.(Signal Generator) to 80dBuV.

3. Set Alignment Scope, Volts/Div to 100mV, AC/DC switch to AC, Line/Ext switch to Ext.

38.9MHz

Signal generator

GND

12Vdc

Power Supply

GND(C26(-))

Ceramic CAP. 10000pF

Fig.1: Connection Diagram of Equipment for BG VCO Adjustment

MAIN BOARD

Z101

4 5

G3962

C25(+)

C25(-)

IC101 TDA4474

J77

R124

L107

C123(+)

J169 5V

R139

Multimeter & oscilloscope

2.5Vdc

SW1

AM/FM SW

GND

SW2

L/L'SW

* VCO (Voltage Controlled Oscillation) Adjustment

a) For B/G system

Test Poin t : Pin 24 of IC101 (+ lead of C123)

Adjust : L107

1) Turn on DC power supplies.

2) Adjust VCO adjust

coil(L107)so that DMM reads 2.5Vdc+_0.1V.

Ceramic CAP.

33.9MHz

Signal generator

GND

12Vdc

Power Supply

GND(C26(-))

10000pF

Ceramic CAP. 10000pF

Fig. 2 : Connecting Diagram of Equipments for secam-L' system.

b) For Secam-L' system

MAIN BOARD

Z102

4 5

G3953

C25(+)

C25(-)

IC101 TDA4474

J77

R124

VR102

C123(+)

J139 GND

R169

Multimeter & oscilloscope

2.5Vdc

GND(C122(-))

SW1

AM/FM SW

SW2

L/L'SW

Test Poin t : J5 (one lead of R533)

Adjus t : VR102

1) Turn on DC power supplies.

2) Apply 5Vdc to the + lead of C25.

3) Adjust VCO adjust

volume(VR102) so that the DMM reads 2.5Vdc+_0.1V.

* Screen voltage adjustment

1) Tune the TV set to receive digital pattern.

2) Press PSM button on the Remote Controller to get the STANDARD picture.

3) Turn the screen VR of FBT until the black level of picutre signal is 150Vdc at the digital pattern.

CPT BOARD

GND Rk

BLACK Level

150Vdc 1.5V

OSCILLSCOPE

Fig. 3 Fig. 4

* RF AGC (Auto Gain Control) Adjustment

TUNER

Test Poin t : J173 or Observing Display

Adjus t : VR101

MAIN BOARD

AGC TP.

6Vdc

Digital Multimeter

The RF AGC contro l(VR101)was aligned at the time of manufacture for optimum performance over a wide range conditions. Readjust of VR101 should not be necessary unless unusual local conditions exist, such as ;

1) Channel interference in a CATV system

2) Picture bending and/or color beats, which are unusually due to excessive RF signal input when the receiver is too close to a transmitting tower or when the receiver is connected to an antenna distribution system where the RF signal has been amplified. In this case, the input signal should be attenuated (with pad or filter) to a satisfactory level.

3) Picture noise caused by “broadcast noise” or weak signal. If the broadcast is “clean” and the RF signal is at least 1mV (60dBu), the picture will be noise free in any area.

J173

Fig. 5

VR101

(AGC ADJ.)

Adjusting th e Adjusting to the other end of rotation will usually cause a degradation of over load capabilities resulting in color beats or adjacent channel reference.

For best results,

(RF level: 60dBuV).

VR101 (RF AGC)control to one end of rotation will usually cause a relatively poor signal to noise ratio;

adjust VR101 control while performing on all other local channels, or the voltage at J173 will be 6.0+_0.1Vdc.

* Focus Adjustment

NOTE : This adjustment should be performed after warming up for 10 minutes.

Test Poin t : Observing Display

Adjus t : Focus control of FBT

1) Set color & brightness to minimum, contrast to 50% respectively.

2) Input the PAL BG Digital Pattern signal.

3) Adjust the Focus control for best overall focus.

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).

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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.

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