Service Manuals, User Guides, Schematic Diagrams or docs for : LG TV LG PC-63A Chassis
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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.
MAIN BOARD
Ceramic
CAP.
38.9MHz 10000pF
IC101 Multimeter &
Signal TDA4474 oscilloscope
generator 2.5Vdc
Z101 L107
Ceramic 3 4 5 G3962
CAP. C123(+)
10000pF 24
GND
C25(+) J77 J169 5V
12Vdc
Power
Supply SW1
AM/FM SW
GND(C26(-)) C25(-)
R124 R139 GND
SW2
L/L'SW
Fig.1: Connection Diagram of Equipment for BG VCO Adjustment
* 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 MAIN BOARD
CAP.
33.9MHz 10000pF
IC101 Multimeter &
Signal TDA4474 oscilloscope
generator 2.5Vdc
Z102 VR102
Ceramic 3 4 5 G3953
CAP. C123(+)
10000pF 24 GND(C122(-))
GND
C25(+) J77 J139 GND
12Vdc
Power
Supply SW1
AM/FM SW
GND(C26(-)) C25(-)
R124 R169 5V
SW2
L/L'SW
Fig. 2 : Connecting Diagram of Equipments for secam-L' system.
b) For Secam-L' system
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.
* Scr een v oltage 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.
BLACK Level
CPT BOARD
GND
Rk
150Vdc 1.5V
OSCILLSCOPE
Fig. 3 Fig. 4
* RF AGC (Auto Gain Control) A djustment
Test Poin t : J173 or Observing Display
Adjus t : VR101
MAIN BOARD
AGC TP.
TUNER
J173 VR101
6Vdc (AGC ADJ.)
Digital
Multimeter
Fig. 5
The RF AGC contro (VR101) was aligned at the time of manufacture for optimum performance over a wide range
l
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.
Adjusting th VR101 (RF AGC) control to one end of rotation will usually cause a relatively poor signal to noise ratio;
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, adjust VR101 control while performing on all other local channels, or the voltage at J173 will be 6.0+_0.1Vdc.
(RF level: 60dBuV).
* Focus A djustment
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 5. Reconnect the internal degaussing coil.
attempt to tamper with these alignments.
However, the effects of adjacent receiver components, or 6. Position the beam bender locking rings at the 9 o'clock
replacement of picture tube or deflection yoke may require the position and the other three pairs of tabs (2,4 and 6 pole
need to readjust purity any convergence. magnets) at the 12 o'clock position.
DEFLECTION YOKE 6-POLE
PURITY &CONVERGENCE 6-POLE
MAGNETS
MAGNES PURITY MAGNET(2-POLE)
MAGNET ASSEMBLY
6-POLE
,,,,
,,,, ,
,,,, ,
,,,, , ,
,,,,
,,,,
,,,, 4-POLE
X-AXIS YOKE MAGNET
,
,,,, , ,,,,
,,,, , ,, ,
,, ,,
,,,, , ,, ,,
,,,, , ,
,,,,
,, , POSITIONING
(L/R PURITY)
RUBBER
WEDGES PURITY MAGNET
4-POLE
GLASS CLOTH TAPE CONVERGENCE MAGNET ASSEMBLY
CONVERGENCE MAGNET ASSEMBLY
* Purity Adjustment
This procedure DOES NOT apply to bonded yoke and picture 7. Perform the following steps, in the order given, to prepare the
tube assemblies. receiver for the purity adjustment procedure.
The instrument should be at room temperature (60 degrees F or
above) for six (6) hours and be operating at low beam current a. Face the receiver in the "magnetic north" direction.
(dark background) for approximately 20 to 30 minutes before
performing purity adjustments. b. Externally degauss the receiver screen with the television
power turned off.
CAUTION: Do not remove any trim magnets that may be
attached to the bell of the picture tube. c. Turn the television on for approximately 10 seconds to
perform internal degaussing and then turn the TV off.
1. Remove the AC power and disconnect the internal
degaussing coil. d. Unplug the internal degaussing coil. This allows the
thermistor to cool down while you are performing the purity
2. Remove the yoke from the neck of the picture tube. adjustment. DO NOT MOVE THE RECEIVER FROM ITS
"MAGNETIC NORTH" POSITION.
3. If the yoke has the tape version beam bender, remove it and
replace it with a adjustable type beam bender (follow the e. Turn the receiver on and obtain a red raster by increasing
instructions provided with the new beam bender) the red bias control (CW) and decreasing the bias controls
for the remaining two colors (CCW).
4. Replace the yoke on the picture tube neck, temporarily
remove the three (3) rubber wedges from the bell of the f. Attach two round magnets on the picture tube screen at 3
picture tube and then slide the yoke completely forward. 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 2 .ADJUST BEAM BENDER 2 POLE
TO GET EQUAL BLUE MAGNET TO GET FOUR EQUAL
COLOR CIRCLES COLOR CIRCLES
MAGNETS
RED RED
8. Referring to above, perform the following two steps: 6. Reconnect the internal degaussing coil and apply AC power.
a. Adjust the yoke Z-axis to obtain equal blue circles.
b. Adjust the appropriate beam bender tabs to obtain correct 7. Turn the receiver on for 10 seconds to perform internal
purity (four equal circles). degaussing and then turn the receiver off again.
9. After correct purity is set, tighten the yoke clamp screw and 8. Unplug the internal degaussing-coil.
remove the two screen magnets.
9. Turn on the receiver, connect a signal generator to the VHF
10. Remove the AC power and rotate the receiver 180 degrees antenna terminal and apply a crosshatch signal.
(facing "magnetic south").
Caution: During the convergence adjustment procedure, be
11. Reconnect the internal degaussing coil. very careful not to disturb the purity adjustment tabs
are accidentally move, purity should be confirmed
12. Turn the receiver on for 10 seconds (make sure the receiver before proceeding with the convergence adjustments.
came on) to perform internal degaussing, and then turn the
receiver off. Note: Make sure the focus is set correctly on this instrument
before proceeding with the following adjustment.
13. Unplug the internal degaussing coil.
10. Converge the red and blue vertical lines to the green vertical
14. Turn on the receiver and check the purity by holding one (1) line at the center of the screen by performing the following
round magnet at the 3 o'clock and a second round magnet at steps (below TABLE).
9 o'clock position. If purity is not satisfactory, repeat steps 8 a. Carefully rotate both tabs of the 4-pole ring magnet
through 14. simultaneously in opposite directions from the 12 o'clock
position to converge the red and blue vertical lines.
15. Turn off the receiver and reconnect the internal degaussing b. Carefully rotate both tabs of the 6-pole ring magnet
coil. 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.
* Convergence Adjustment
11. Converge the red and blue horizontal with the green line at
Caution: This procedure DOES NOT apply to bonded yoke and the center of the screen by performing the following steps.
picture tube assemblies. (below TABLE)
Do not use screen magnets during this adjustment a. Carefully rotate both tabs of the 4-pole ring magnet
procedure. Use of screen magnets will cause an simultaneously in the same direction (keep the spacing
incorrect display. between the two tabs the same) to converge the red and
blue horizontal lines.
1. Remove AC power and disconnect the internal degaussing b. Carefully rotate both tabs of the 6-pole ring magnet
coil. simultaneously in same direction (keep the spacing
between the two tabs the same) to converge the red and
2. Apply AC Power and set the brightness to the Picture Reset blue (now purple) horizontal lines with the green
condition. Set the Color control to minimum. horizontal line.
c. Secure the tabs previsouly adjusted by locking them in
3. Apply 8V to the pin. 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
RING ROTATION DIRECTION MOVEMENT OF RED
PAIRS OF BOTH TABS AND BLUE BEAMS
B B
OPPOSITE OR
R R
4
POLE
SAME B R OR B R
B B
OPPOSITE OR
R R
6
POLE
SAME B R OR B R
UP/DOWN ROCKING OF THE YOKE LEFT/RIGHT ROCKING OF THE YOKE
UP/DOWN ROCKING OF THE YOKE
CAUSES OPPOSITE ROTATION OF RED CAUSES OPPOSITE SIZE CHANGE YOKE
LEET/RIGHT ROCKING OF THE OF THE
AND BLUEOPPOSITE ROTATION OF RED
CAUSES RASTERS RED AND BLUE RASTERS CHANGE OF
CAUSES OPPOSITE SIZE
AND BLUE RASTERS THE RED AND BLUE RASTERS
GREEN
GREEN
ADJUSTMENT
VIEWING ADJUSTMENT RED
AREA BLUE RED VIEWING
AREA
RED
GREEN RED BLUE
BLUE RED
GREEN
RED BLUE
TV
SCREEN
GREEN
12. While watching the 6 o'clock positions on the screen, rock the 17. Temporarily place a rubber wedge at the 5 o'clock and 7
front of the yoke in a vertical (up/down) direction to converge o'clock positions to hold the horizontal position of the yoke.
the red and blue vertical lines. (Fig upper left) 18. Check the 3 o'clock and 9 o'clock areas to confirm that the
13. Temporarily place a rubber wedge at the 12 o'clock position red and blue vertical lines are converged. If the lines are not
to hold the vertical position or the yoke. converged, slightly offset the horizontal tilt of the yoke (move
14. Check the 3 o'clock and 9 o'clock areas to confirm that the red the temporary rubber wedges if necessary) to equally
and blue horizontal lines are converged. balance the convergence error of the horizontal lines at 6
If the lines are not converged, slightly offset the vertical tilt of the o'clock and 12 o'clock and the vertical lines at 3 o'clock and 9
yoke (move the rubber wedge if necessary) to equally balance the o'clock.
convergence error of the horizontal lines at 3 o'clock and 9 o'clock 19. Using a round magnet confirm purity at the center, right and
and the vertical lines at 6 o'clock and 12 o'clock. left sides and corners. See Purity Adjustment Procedure.
15. Place a 1.5 inch piece of glass tape over the rubber foot at 20. Reconfirm convergence and apply a 1.5 inch piece of glass
the rear of the 12 o'clock wedge. tape over the rubber foot at the rear of the 5 o'clock and the 7
16. While watching the 6 o'clock and 12 o'clock areas of the o'clock wedges.
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)
3-4
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