LG-CB20T20X – TDA8841 or TDA8842 – LG WP32A30 – CXA1855S, CXA2050S – Service mode, Options adjustment and schematics

 

RF AGC (Automatic Gain Control) Adjustment,  Test Point - AGC TP (J05).  Adjust - Remote Control

The RF AGC was aligned at the time of manufacture for optimum performance over a wide range conditions.  Readjustment of RF AGC 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 RF AGC 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 in color beats or adjacent channel interference.

Adjustment

1. Connect RF signal (65dB!0.2dB) and turn on the TV. [ Standard adjustment Channel]
- EU 05 Ch. (frf = 175.25MHz) : CK, CL, CB
- EU 41 Ch. (frf = 631.25MHz) : CI
2. Press OK buttons on TV set and Remote Controller at the same time to get into SVC-0 mode.
3. Press Channel UP/DOWN button on the Remote Controller several times to find AGC?
4. Press Volume UP/DOWN button until the AGC Voltage is the same as the Table below.
5. Press OK button to memorize the data.

Service mode

To enter SVC mode, press "OK" buttons on both TV set and the Remote control at the same time.

Preparation for Deflection Adjustment
1) At SVC mode, press the Yellow colored button.  If the Remote Controller doesn't have the Yellow button, you should use a Service Remote Control (105-201G) and press SVC button.
And then, deflection data adjustment OSD (SVC1 mode) will be displayed.
2) Press Channel UP/DOWN button for desirous function
Adjustment.
3) Press Volume UP/DOWN button to adjust the data.

Vertical Adjustment
Select VS and adjust until the mechanical centre of CPT and that of screen coincides and select VA and adjust to coincide the inner circle of screen with outer frame of CPT.

2) Horizontal Adjustment
Select HS and adjust until the mechanical centre of CPT and that of screen coincides.

3) Vertical S Correction Adjustment
Select SC and adjust until top-bottom side pincushion are equal.

4) Press OK button to memorize the data.

White Balance Adjustment.(LINE SVC-0)

[This adjustment should be performed after screen voltage adjustment.]

Tune the TV set to receive an 100% white pattern.
2) Press OK(Y) buttons on TV set and remote controller at the same time to get into SVC mode.
3) Press PSM(RED) button on remote controller. (Standard picture)
4) Press Channel UP/DOWN button for desirous function adjustment.
5) Adjust VOL+ or VOL- button for GG031.
6) Adjust VOL+ or VOL-button in each status of "Rg--" "Bg--" for
X=293!8, Y=295!8 with color analyzer.
7) Press OK button to memorize the adjustment data.

OPTION Adjustment (SVC MODE: OPTION-1, OPTION-2)

[When the EEPROM has been replaced, the Option data should be restored as the function of individual system and specification.]

Press OK buttons on both TV set and Remote Controller at the same time to get into SVC mode.
2) Press the Yellow button several times to find OPTION-1 or OPTION-2.
3) Input the correspond OPTION data referring to Table below with the numeric buttons 0~9.

LG-CB20T20X schematic

LG WP32A30 SCHEMATIC

LG WP32A30 adjustments-service mode

These instructions apply to MC-75A color television chassis.

1. Because this is a cold chassis, it is not necessary to use an insulation transformer. But, operate it using an insulation transformer between the power supply line and chassis input to prevent electric shock and to protect the test instrument.
2. The adjustment must be done by the correct appliances.
3. Unless otherwise noted, the receiver must be operated for about 10 minutes prior to the adjustment.

MPX Adjustment
(1) Connect the Oscilloscope to pin 3 of IC101 on Main PCB.
(2) Input Stereo signal.
(3) Adjust VR101 until the Audio Output waveform is like figure

Sub-Bright Adjustment
(1) Press ADJ button of the Adjustment Remote Control to select S-BRI.
(2) Press VOL +/- of the Adjustment Remote Control for proper Sub-Brightness (Standard :50)

Sub-Color Adjustment
(1) Press ADJ button of the Adjustment Remote Control to select S-COL.
(2) Press VOL+/- of the Adjustment Remote Control for proper Sub-Color. (Standard : 10)

Sub-Tint Adjustment
(1) Press ADJ button of the Adjustment Remote Control to select S-TIN.
(2) Press VOL +/- of the Adjustment Remote Control for proper Sub-Tint (Standard : 6)

TWIN PICTURE BRIGHTNESS (MAIN/SUB)
Adjust VR02 until the Brightness of both MAIN and SUB picture is same.

Focus Adjustment
(1). Input digital Pattern signal.
(2) Press PICTURE button to select standard picture.
(3) Press MODE button to select WIDE mode.
(4) Turn both Upper and Lower Focus control until the best overall focus.

Standard CONTRAST : 85%
BRIGHTNESS : 50%
COLOR : 50%
TINT : 0
SHARPNESS : 50%

Vertical Position Adjustment.
(1) Input Digital Pattern Signal
(2) Press PICTURE button to select standard picture.
(3) Select WIDE mode.
(4) Adjust VR301 on SMPS board for proper position.

H Size Adjustment
(1) Input Digital Pattern Signal.
(2) Press Picture button to select standard picture.
(3) Select WIDE mode.
(4) Adjust VR401 on SMPS board for proper H size.

Deflection setting Data Adjustment
(1) Press MENU and CH up buttons on the drawer together for about 2 seconds to get into Deflection setting mode.
(2) Press CH +/- to select adjustment item.
(3) Press CH +/- to change Data.
(4) Input Digital Pattern Signal and select the standard picture.

Vertical Amplitude Adjustment : Wide mode
(1) Press CH +/- button and select V-ASP.
(2) Press VOL +/- button for the proper amplitude.

Standard mode : Same as Wide mode.
Spectacle mode : Press VOL +/- until (A) of Digital Pattern coincides with upper and Lower frame.
Zoom1 mode : Press VOL +/- until (B) of Digital Pattern coincides with Lower frame.
Zoom2 mode : Press VOL +/- until (C) of Digital Pattern comes 7!3mm from the upper frame.

H Position Adjustment
(1) Press CH +/- button and select H-POS.
(2) Press VOL +/- button until left and right of screen is equal.

WHITE BALANCE Adjustment
(1) Input Digital Pattern signal
(2) Select Wide mode
(3) Press MENU and CH+ buttons on the drawer together for about 2 seconds to get into Deflection setting mode.
(4) Press CH+/- to select adjustment item.
(5) Press VOL +/- to change Data.

(1) Adjust Contrast and Brightness until the highlight area of signal is 30!3.5F.L.

(2) Select G-DRI and B-DRI and adjust to get the Highlight data (X=282!8, Y=288!8).
(3) Adjust Contrast and Brightness until the highlight area of signal is 4.5!0.5F.L.
(4) Select G-CUT and B-CUT and adjust to get the Low light data (X=282!8, Y=288!8).
(5) Repeat adjustment (1)~(4) above to get both Low and High light data.
(6) Check the result of adjustment using White Balance Meter
HIGH LIGHT : X=282!8, Y=288!8
LOW LIGHT : X=282!8, Y=288!8

OSD COLOR :

Green - Adjust at all modes

Cyan - Adjust only WIDE mode

Yellow - Adjust only WIDE mode, correction at other modes.