LG MC-64A Sch. and Adjusments.pdf part of LG LG MC-64A Sch. and Adjusments.rar, Sch. and Adjusments text manual preview

Text preview for : LG MC-64A Sch. and Adjusments.pdf part of LG Sch. and Adjusments

Back to : LG MC-64A Sch. and Adjus | Home

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 220Vac+_ 20%, 50/60Hz.

* VCO (Voltage Controlled Oscillator)
Adjustment
Test Point Adjust JP4(L504) : VL501 :

1) Turn on DC power supplies. 2) Adjust VCO ADJ. coil(L501) so that the level of Picture Carrier (PC) may be at the lowest position as shown Fig. 2.

*T est Equipment required
1. 2. 3. 4. 5. 6. 7. Swee p Generator Marker Generator(38.0MHz: Picture/32.5MHz: Sound) Alignmen t Scope(5121A) Patter n Generator(PAL/SECAM) DC Power Supply Color analyzer Multimeter(Volt meter)

SC (Sound Carrier) : 32.5 MHz

PC (Picture Carrier) : 38.0 MHz
Fig. 2: Output waveform on Alignment Scope

Preparation for VCO Adjustment 1. Connect the measuring equipment to the TV as shown in Fig. 1 2. Set RF output level of Sweep Generator to 90dBuV.

NOTE :

When performing this adjustment, if there are 2 adjusted point in VL501, select the lower core position.

* RF AGC (Auto Gain Control)
MAIN BOARD
C533 (JP 3) Z101 (JP 1) 5 7 CK 0.01uF 3.3K L504 (JP 4) 1 TUNER IC401

Adjustment
Test Point

:J9(AGC ADJ.) or Observing Display :VR501

48

IC501

Adjust

J9 AGC ADJ.

VL501 VCO ADJ.

(JP 6)

The RF AGC control VR501 was aligned at the time of manufacture for optimum performance over a wide range conditions. Readjust VR501 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 reciever 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.

RF out Hor SWEEP S.G with Marker Alignment Scope Ver DC POWER SUPPLY 5.0 + 0.1V DC POWER SUPPLY 16 + 0.5V

Fig. 1: Connection Diagram of Equipment for VCO Adjustment

- 1 -

Adjusting the VR501(RF AGC) control to one end of rotation will usually cause a relatively poor signal to noise ratio; Adjusting to the other end of rotation will usually cause a degradation of over load capabilities resulting on color beats or adjacent channel interference. For the best results, adjust VR501 contol while performing on all other local channels, or Refer to the following Table 1.
Tuner P/N 113-118C/D/F 113-238H Maker Adjustment Voltage REMARK
RF 60+_1dBuV RF 60+_1dBuV RF 60+_1dBuV

* Scr een & White Balance

(color temperature) Adjustment
NOTE: 1. This adjustment should be performed after warming up for 20 minutes. 2. The color bias controls (VR901, VR902, VR903) affect the low light (dark) area of the picture while the color drive controls (VR904, VR905) affect the high light (white) areas. 1) Set all the controls (VR901-VR905) on CPT Board to geometric center position. 2) Set the standard mode (contrast : 80, bright : 60, color : 50). 3) Set the AV mode, adjust and set the screen volume of FBT at just cut-off position(No AV input signal). 4) Set the TV mode, tune the TV set to receive white pattern. 5) By using color analyzer (white balance checker), adjust X position equals to 281+_8 and Y position equals to 288 +_8, it means that color temperature is 10,000+_800 at low light (4.5ftL) and high light (over 45ftL).

LG-ALPS 5.7+_0.1Vdc LG-ALPS 6.0+_0.1Vdc

6700VMV001A SANYO

4.9+_0.1Vdc

* Vertical Height, Center Adjustment
Test Poin t : Observing display Adjust : VR30 (Vertical Height) 1 VR302 (Vertical Center)

1) Tune the TV set to receive a digital test pattern. 2) Set standard picture mode(contrast: 80, bright :60, color: 50). 3) Adjust the Vertical height control (VR301) so that the circle of a digital test pattern may be located within the effective screen of the CPT. 4) Adjust the Vertical center control (VR302) for obtaining geometric center of valuable display vertically.

* Focus A djustment
NOTE: This adjustment should be performed after warming up for 10 minutes. Test Poin t : Observing display Adjust : Focus control of FBT

1) Tune the TV set to receive a digital test pattern. 2) Adjust the Focus control for the best overall focus.

* Horizontal Center Adjustment
Test Poin t : Observing display Adjust : VR502

1) Tune the TV set to receive a PAL digital pattern. 2) Adjust the Horizontal center control(VR502) for obtaining geometric center of valubale display horizontally.

- 2 -

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. 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.

DEFLECTION YOKE PURITY &CONVERGENCE MAGNET ASSEMBLY

6-POLE 6-POLE MAGNETS
MAGNES PURITY MAGNET(2-POLE)

6-POLE
,, ,, ,, ,, ,, , ,,,, ,,,, ,,,,
, ,,,,

RUBBER WEDGES

* 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.

3-2

,, , ,,,, , ,,,, , ,,,, , ,,,, , , ,,,, , ,,,, , ,,,, , ,,,,

, ,,,,

4-POLE X-AXIS YOKE MAGNET POSITIONING (L/R PURITY)

PURITY MAGNET 4-POLE

GLASS CLOTH TAPE

CONVERGENCE MAGNET ASSEMBLY CONVERGENCE MAGNET ASSEMBLY

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).

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

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

MAGNETS

RED

RED

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.

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.

* 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. 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 PAIRS

ROTATION DIRECTION OF BOTH TABS

MOVEMENT OF RED AND BLUE BEAMS

B OPPOSITE 4 POLE SAME B R OR

B R

R

OR

B

R

B OPPOSITE R 6 POLE SAME B R OR OR

B R

B

R

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

AND BLUE RASTERS

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

THE RED AND BLUE RASTERS

GREEN

GREEN
ADJUSTMENT VIEWING AREA

BLUE

RED

ADJUSTMENT VIEWING AREA

RED 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 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.

3-4