LG CF25A64D Service Manual

Troubleshooting Guide

NO RASTER

Check +B voltage at D825 Cathode.

Is the voltage at pin8 and

37 of IC501 8V?

Check pin40 of IC501 (H-Out).

Check Q451

Collector waveform.

Check Q452

Collector waveform.

Check T401 &

each pin voltage.

Check

Fuse of AC line.

Check the voltage of

C808.

Check the voltage

at pin9 of IC801.

Check/replace

IC803, D824 and D835.

Check/replace

IC501.

Check/replace Q451,

T451 and R452.

Check/replace

Q452.

Check the in/output

of IC607.

Check the IIC Bus

Line (SDA,SCL) pin3

and 4 of IC501.

Check/replace

Fuse, D801 and

IC801.

Check/replace

R801 and D801.

Check D802,

D805, D807, Q801

and IC801.

Normal

Yes

254~380V

Lower than 6V

Open

Abnormal

NO SOUND

(PICTURE OK)

Select correct

system in MENU

Check L System

is right?

AM NO SOUND NICAM,FM NO SOUND

Abnor mal

Not OK

Yes

Not OK

Normal

Check the logic of

pin3 and 15 of

IC101.

Check/replace

Z104 & +B of

IC101.

Check the AM

Line.

(pin27 of IC101)

Check AM Input of

IC601, pin44.

Check/replace

pin14 & 25 of

IC01.

Check Sound

system in MENU

OSD.

Select correct

system in MENU.

Check

pin47 of IC601.

Check X601 & pin16 and 46 of IC601, IIC

Bus Line.

Check/replace

X601 and IC601.

Check C607

& R601.

Check pin14

& 25 of IC01.

Check demodulated

SIF signal (pin26 of

IC101).

Check the logic of

pin3 and 15 of

IC101.

Check R, L input

of IC651, pin2 and

Check +B of

IC651

& D822.

Is any OSD

displayed?

Check R,L Out

of IC601.

Check Z103,

Q102

& pin25 of IC101.

NO PICTURE

NO SOUND

Is any OSD displayed?

Go to

NO RASTER (SOUND OK).

Go to

NO SOUND.

Check receiving system in

MENU & excute Auto-

programme.

Does the Auto-programme

operate properly?

Direct Input channel number

& store in manual-program

MENU.

And Check 5V, 12V, 33V &

IIC Bus Line of TUNER.

Is the CVBS signal

OK (pin 14 of IC101).

Check pin9 and 18 of

MICOM IC01.

Check IC01 &

H-Sync Line.

Check 5V, 12V,

33V

& IIC Bus Line.

Go to NO SOUND

PICTURE OK.

Yes

Not OK

OKOK

Yes

NO RASTER

(SOUND OK)

OK OK

OKOK

Not OK

Not OKNot OK

Check the

Heater voltage of CPT(6-6.5Vrms).

Check

the HEATER pulse of FBT

T401.

Check

FR405,FR901 & P402.

Check

FBT T401.

Check

lk Current of IC501,pin18.

Check

HV,SCREEN voltage of

CPT.

Check

P501,ZD564 & IC501.

Check/replace

CPT Board components.

Check/replace

FBT T401.

NO PICTURE

NO COLOR

Is the CVBS signal at pin14 of

IC101 normal?

Check Receiving system in

MENU & go to NO PICTURE,

NO SOUND.

Check the state of pin11 and 13

of IC201,L201 and R206(+B of

IC201).

Check/replace

Q201,L603(12V) & CVBS Line.

Check pin9 of IC501, IC702

IIC Bus Line & Q701.

Check IC502, L542

& pin26 of IC501.

Check X501, IC503, L541,

ZD541 & IC504(In case of

SECAM system).

Is the CVBS signal at pin16 of

IC201 normal?

Is the CVBS signal at pin 13 of

IC501 normal?

Is the CVBS signal at pin 2 of

IC702 normal?

Is the CVBS signal at pin11 of

IC501 normal?

Is the Y signal at pin 27 of

IC501 normal?

Check if R-Y and B-Y signal of

pin32 and 33 of IC501 are

normal?

Yes

NO TELETEXT

Check the voltage of

pin7, 16 and 21 of IC701.

Check CVBS signal at pin2

of IC702 & X701.

Check IC701, 702 & IIC Bus

Line (SDA, SCL).

Check 5V & 12V Supply

Line of IC701 and 702.

And check pin803B & Power

Line (MAIN2 PCB).

Check/replace Q701, X701

& IC501.

Not OK

ADJUSTMENT INSTRUCTIONS

YSafety 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.

YTest Equipment required

1. RF signal generator (with pattern generator)

2. DC Power Supply

3. Multimeter (volt meter)

4. Oscilloscope

5. Color analyzer

PIF (Picture Intermediate Frequency) Adjustment

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

2) Set RF frequency and output level of RF SIGNAL

(Table 1)

T SECAM-L' Adjustment

NOTE : This adjustment should be performed after PIF

adjustment.

1) Turn on S1 and S3 and off S2.

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

3.1

!0.1Vdc.

IC01

TP1

JP7 IC05

IC102

JP3

JP5 JP6

Q106

4.7k½

100½

VR101

103pF

Signal- Generator

JP1

L107

VR102

38.9MHz

33.9MHz

Power- Supply

V Multimeter or Oscilloscope

JP2

JP4

Test Point : TP1

Adjust : L107

Test Point : TP1

Adjust : VR102

Frequency

38.9MHz

33.9MHz

System

B/G/SECAM-L

SECAM-L'

Modulation

OFF

Output level

10mVp-p

Adjust

L107

VR102

Main Board(Component side view)

Fig. 1 : Connection Diagram of Equipment for PIF Adjustment

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

Adjustment (LINE SVC 1)

Adjustment Procedures

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

2) 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.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.

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.

VH--(Vertical Height)

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.

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.

T White Balance Adjustment.(LINE SVC 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

8, Y=295!8 with color analyzer (color temperature

9000

cK).

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.

[LINE SVC1] 1

CH5

VL 31 EW 40 VH 42 EP 44 SC 31 EC 31 VS 33 ET 31 HS 20 50HZ*

*: This is only displayed according to

receiving system. PAL/SECAM System : 50Hz NTSC System : 60Hz

[

RF AGC (Automatic Gain Control) Adjustment

The RF AGC control (VR101) was aligned at the time of manufacture for optimum performance over a wide range conditions. Readjustment 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 the VR101(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 in color beats or adjacent channel interference. For best results, adjust the VR101 control while performing on all over local channels, or the voltage at TP2 will be 6.5

!0.1Vdc in RF level 60!1dBuV.

T Screen Voltage Adjustment

1) Tune the TV set to receive a digital pattern.

2) Press PSM (RED) button on remote controller. (standard picture)

3) Connect the probe of oscilloscope to the RK (Red Cathode) of CPT Board.

4) Adjust Screen Volume of FBT so that the waveform is the same as below Fig. 6.

T Focus Adjustment

NOTE: This adjustment should be performed after warming

up for 10 minutes.

1) Tune the TV set to receive an inactive channel station.

2) Adjust the Focus control of FBT for best overall focus.

Test Point : TP2 (J8) or Observing Display

Adjust : VR101

Test Point : RK (Red Cathode of CPT Board)

Adjust : Screen Control of FBT

Test Point : Observing Display

Adjust : Focus control of FBT

Horizontal FlyBack Time

Black level

White level

170Vp-p

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