LG CB777F-AA, CB777F-NA, LN777F, CB777F-EA, StudioWorks 700S Service Manual

COLOR MONIT OR

SER VICE MANUAL

Website:http://biz.LGservice.com

E-mail:http://www.LGEservice.com/techsup.html

CAUTION

BEFORE SERVICING THE UNIT,
READ THE SAFETY PRECAUTIONS IN THIS MANUAL.

MENU SELECT

MODEL:

StudioWorks 700S (CB777F-NA), StudioWorks 700E (CB777F-AA)
StudioWorks 700B (CB777F-EA), LN777F(LN777F)

CHASSIS NO. : CA-90

F ACTORY MODEL: CB777F

*( ) ID LABEL Model No.

1. PICTURE TUBE

Size : 17 inch (Flat Square Tube)
DefIection Angle : 90°
Neck Diameter : 29.1 mm
Dot Pitch : 0.27 mm
Face Treatment : W-ARASC (Anti-Reflection and

Anti-Static Coating),

Anti-static coating

Low Radiation : MPR II, TCO 99

2. SIGNAL

2-1. Horizontal & Vertical Sync

1) Input Voltage Level: Low=0~1.2V, High=2.5~5.5V

2) Sync Polarity : Positive or Negative

2-2. Video Input Signal

1) Voltage Level : 0 ~ 0.7 Vp-p
a) Color 0, 0 : 0 Vp-p
b) Color 7, 0 : 0.467 Vp-p
c) Color 15, 0 : 0.7 Vp-p

2) Input Impedance : 75 Ω

3) Video Color : R, G, B Analog

4) Signal Format : Refer to the Timing Chart

2-3. Signal Connector

3 row 15-pin Connector (Attached)

2-4. Scanning Frequency

Horizontal : 30 ~ 70 kHz
Vertical : 50 ~ 160 Hz

3. POWER SUPPLY

3-1. Power Range

AC 100~240V (Free Voltage), 50/60Hz, 2.0A Max.

3-2. Power Consumption

4. DISPLAY AREA

4-1. Active Video Area :

• Max Image Size - 326.7 x 245.5 mm (12.86" x 9.67")

• Preset Image Size - 310 x 230 mm (12.20" x 9.06")
4-2. Display Color : Full Colors
4-3. Display Resolution : 1280 x 1024 / 60Hz

(Non-Interlace)

4-4. Video Bandwidth : 110 MHz

5. ENVIRONMENT

5-1. Operating Temperature: 15°C ~ 30°C (59°F ~ 86°F)

(Ambient)

5-2. Relative Humidity : 8%~ 80%

(Non-condensing)

5-3. Altitude : 5,000 m

6. DIMENSIONS (with TILT/SWIVEL)

Width : 400.0 mm (15.74 inch)
Depth : 420.0 mm (16.53 inch)
Height : 395.0 mm (15.55 inch)

7. WEIGHT (with TILT/SWIVEL)

Net Weight : 14.4 kg (31.75 lbs.)
Gross Weight : 17.0 kg (37.48 lbs.)

CONTENTS

- 2 -

SPECIFICATIONS ................................................... 2

SAFETY PRECAUTIONS ........................................ 3

TIMING CHART ....................................................... 4

OPERATING INSTRUCTIONS ................................ 5

CONTROL LOCATIONS ......................................... 6

WIRING DIAGRAM ................................................. 7

DISASSEMBLY ....................................................... 8

BLOCK DIAGRAM ................................................. 11

DESCRIPTION OF BLOCK DIAGRAM...................12

ADJUSTMENT ...................................................... 14

TROUBLESHOOTING GUIDE .............................. 16

EXPLODED VIEW...................................................26

REPLACEMENT PARTS LIST ............................... 28

PIN CONFIGURATION........................................... 34

SCHEMATIC DIAGRAM......................................... 36

PRINTED CIRCUIT BOARD................................... 38

SPECIFICATIONS

MODE

MAX

NORMAL (ON)

STAND-BY

SUSPEND

OFF

POWER CONSUMPTION

100 W

74 W
less than 15 W
less than 15 W
less than 5 W

LED COLOR

GREEN
GREEN

AMBER

AMBER

SAFETY-RELATED COMPONENT WARNING!

There are special components used in this color monitor
which are important for safety. These parts are marked

on the schematic diagram and the replacement

parts list. It is essential that these critical parts should be

replaced with the manufacturer's specified parts to
prevent X-radiation, shock, fire, or other hazards. Do not
modify the original design without obtaining written
permission from LG or you will void the original parts and
labor guarantee.

CAUTION:

No modification of any circuit should be
attempted.
Service work should be performed only after
you are thoroughly familiar with all of the
following safety checks and servicing
guidelines.

SAFETY CHECK

Care should be taken while servicing this color monitor
because of the high voltage used in the deflection circuits.
These voltages are exposed in such areas as the
associated flyback and yoke circuits.

FIRE & SHOCK HAZARD

An isolation transformer must be inserted between the

color monitor and AC power line before servicing the
chassis.

• In servicing, attention must be paid to the original lead
dress specially in the high voltage circuit. If a short
circuit is found, replace all parts which have been
overheated as a result of the short circuit.

• All the protective devices must be reinstalled per the
original design.

• Soldering must be inspected for the cold solder joints,
frayed leads, damaged insulation, solder splashes, or
the sharp points. Be sure to remove all foreign
materials.

IMPLOSION PROTECTION

All used display tubes are equipped with an integral
implosion protection system, but care should be taken to
avoid damage and scratching during installation. Use only
same type display tubes.

X-RADIATION

The only potential source of X-radiation is the picture tube.
However, when the high voltage circuitry is operating
properly there is no possibility of an X-radiation problem.
The basic precaution which must be exercised is keep the
high voltage at the factory recommended level; the normal
high voltage is about 25.5kV. The following steps describe
how to measure the high voltage and how to prevent X­radiation.

Note : It is important to use an accurate high voltage

meter calibrated periodically.

• To measure the high voltage, use a high impedance
high voltage meter, connect (–) to chassis and (+) to
the CDT anode cap.

• Set the brightness control to maximum point at full
white pattern.

• Measure the high voltage. The high voltage meter
should be indicated at the factory recommended level.

• If the meter indication exceeds the maximum level,
immediate service is required to prevent the possibility
of premature component failure.

• To prevent X-radiation possibility, it is essential to use
the specified picture tube.

CAUTION:

Please use only a plastic screwdriver to protect yourself
from shock hazard during service operation.

SAFETY PRECAUTIONS

- 3 -

TIMING CHART

- 4 -

VIDEO

SYNC

C

E

D

F

AB

MODE

Resolution

Recall

H
O
R

I
Z
O
N
T
A
L

V
E

R

T

I
C
A

L

kHz

µs
µs
µs
µs
µs
µs

Hz
ms
ms
ms
ms
ms
ms

MODE 2

+

46.88

21.33

16.16

5.17

0.32

1.62

3.23
+

75.01

13.331

12.798

0.533

0.021

0.064

0.448

800

x

600

75Hz

Yes

MODE 1

—

37.50

26.67

20.32

6.35

0.51

2.03

3.81

—

74.99

13.335

12.802

0.533

0.026

0.080

0.427

640

x

480

75Hz

Yes

MODE 3

+

53.68

18.63

14.22

4.41

0.57

1.14

2.70
+

85.07

11.775

11.178

0.577

0.018

0.056

0.503

800

x

600

85Hz

Yes

MODE 4

+

68.677

14.561

10.836

3.725

0.508

1.016

2.201
+

85.00

11.764

11.182

0.582

0.014

0.044

0.524

1024

x

768

85Hz

Yes

MODE 5

—

31.47

31.78

25.42

6.36

0.64

3.81

1.91
+

70.08

14.269

12.712

1.557

0.414

0.063

1.080

640

x

400

70Hz

Yes

MODE 6

—

31.47

31.78

25.42

6.36

0.64

3.81

1.91

—

59.94

16.684

15.254

1.430

0.318

0.063

1.049

640

x

480

60Hz

Yes

MODE 7

+

37.88

26.40

20.00

6.40

1.00

3.20

2.20
+

60.32

16.579

15.840

0.739

0.026

0.106

0.607

800

x

600

60Hz

Yes

MODE 8

—

43.269

23.112

17.778

5.334

1.556

1.556

2.222

—

85.008

11.764

11.093

0.670

0.023

0.069

0.578

640

x

480

85Hz

Yes

MODE 9

—

49.75

20.10

14.52

5.58

0.55

1.12

3.91

—

74.95

13.407

12.542

0.865

0.021

0.060

0.784

832

x

624

75Hz

Yes

MODE 10

+

60.02

16.66

13.00

3.66

0.20

1.22

2.24
+

75.03

13.328

12.795

0.533

0.017

0.050

0.466

1024

x

768

75Hz

Yes

MODE 11

+

63.98

15.63

11.85

3.78

0.44

1.04

2.30
+

60.02

16.661

16.005

0.656

0.015

0.047

0.594

1280

x

1024

60Hz

Yes

MARK

E
A
B
C

D
F

E
A
B
C

D
F

Sync Polarity

Frequency

Total Period

Video Active Time

Blanking Time

Front Porch

Sync Duration

Back Porch

Sync Polarity

Frequency

Total Period

Video Active Time

Blanking Time

Front Porch

Sync Duration

Back Porch

FACTORY PRESET MODE

* Mode 1~Mode 4: Preset Mode (Mode 5~Mode 11: Default Mode)

OPERATING INSTRUCTIONS

- 5 -

MENU SELECT

FRONT VIEW REAR VIEW

AC Power Socket

Signal Connector

ID Label

Power ON/OFF Button

See Front Control Panel

Front Control Panel

1. Power ON/OFF Button

Use

this button to turn the monitor ON or OFF.

2. Power Indicator

This indicator lights up green when the monitor operates
normally; in DPMS (Energy Saving) mode, - stand-by,
suspend, or power off mode - its color changes to orange,
and if abnormal or damaging circuit turns out orange blink.

3. Select Button

Use this button to enter a selection in the on screen
display.

4. Button

Use these buttons to choose or adjust items in the on
screen display.

5. MENU Button

Use this button to enter or exit the on screen display.

MENU SELECT

4

5

1

2

3

CONTROL LOCATIONS

- 6 -

MAIN

FBT

CONTROL

1

2

3

4

5

7

6

8

NO.

1

2

3

4

5

Ref. No.

SW207

SW204

SW205

SW203

SW206

NO.

6

7

8

Ref. No.

SW202

SW201

VR901

Control Function

POWER

BUTTON

OSD SELECT

OSD ADJUSTMENT(UP)

OSD ADJUSTMENT(DAUN)

OSD ADJUSTMENT(LEFT)

Control Function

OSD ADJUSTMENT(RIGHT)

MENU BUTTON

B+ ADJUSTMENT

WIRING DIAGRAM

- 7 -

P501

P201

CABINET

P405

P102

P301

P302

P702

P402

P902

S

+

S

TO G2

Signal
Cable

AC
Socket

FBT

DISASSEMBLY

- 8 -

1. TILT/SWIVEL & BACK COVER REMOVAL

1) Set the monitor face downward.

2) Pressing the latch (a), carefully remove the Tilt/Swivel by pulling it upward.

3) Pressing the latch (b), Back cover by pushing it upward.

4) Release the latch (c).

5) Slide the Back Cover away from the Front Cabinet of the monitor.

Tip Spec.

A(Width) : 5.0~15.0mm
B(Depth) : 0.6~0.9mm
C(Height) : 10.0mm

Back Cover

(c)

Cabinet

(a)

C

Tip

B

A

(b)

1

3

2

3

2

- 9 -

(b)

(a)

(a)

(a)

P302

P301

3. VIODEO PCB ASSEMBLY REMOVAL

1) Disconnect P301, P302 from the Video PCB.

2) Remove three connects (a).

3) Remove screws (b).

4) Remove the Video PCB Assembly.

2. TOTAL CHASSIS ASSEMBLY REMOVAL
(

Figure.1)

1) Carefully separate the CDT Board

Assembly from the CDT neck.

2) Discharge the remaining static electricity

by shorting between the Anode Cap and
the CDT ground.

3) Disconnect the Anode Cap from the

CDT.

4) Disconnect P902 (Degaussing pin),

P701 (DY pin), and P501, P405 from
the Main PCB.

5) Remove the Total Chassis

Assembly from the Main Frame.

(

Figure.2)

6) Set the monitor face downward.

7) Pressing the latch (a), Main Chassis

by pushing it upward.

Anode Cap

P501

to Tilt coil

(P501)

Degaussing pin

(P902)

P902

T

P701

P201
(Control PCB)

P405

(a)

(a)

CDT

Figure.1

Figure.2

- 10 -

(b)

(b)

(b)

(a)

(a)

5. BOTTOM BRACKET REMOVAL

1) Remove two holer (a).

2) Remove three screw (b).

3) Remove the Bottom Bracket.

MENU

SELECT

(a)

4. CONTROL PCB ASSEMBLY REMOVAL

1) Remove the screw (a).

2) Remove the Control PCB.

BLOCK DIAGRAM

- 11 -

OSD

ON/OFF

SELECT

POWER

POWER INPUT

100~240VAC

(50/60Hz)

Line

Filter

Degaussing

Circuit

< OSD Control >

SMPS

TRANS

(T901)

SMPS

CONTROL

(IC901)

DPM

CONTROL

CIRCUIT

5V

Voltage

Regulating

Circuit

80V

50V 15V

6.3V

TILT

Control

Circuit

6.3V

15V

E

2

PROM

(IC402)

H / V POSITION

H / V SIZE

SPCC

TRAPIZODE

PIN BALANCE

PARALLELOGRAM

ROTATION

RECALL

DEGAUSS

DDC OPTION

COLOR CURVE

MOIRE

LANGUAGE

RECALL

VIDEO LEVEL

BRIGHTNESS CONTROL

OSD POSITION

5V

OSD IC

(IC301)

H-Sync Sig

V-Sync Sig

I

2

C DATA(SDA)

I

2

C CLOCK(SCL)

VIDEO

PRE-AMP

(IC302)

Signal

Cable

R

G

B

VIDEO

CUT OFF IC

(IC304)

MAIN AMP

(IC303)

5V

5V

H/V Sync Processor

( IC701 )

TDA4841

V-OUT

( IC601)

TDA4866

H-OUT

( Q706)

H-Linearity

Correction

Screen Control

Circuit

DC/DC Converter

X-RAY

Protection

Circuit

FBT

( T701 )

Dynamic

Focus

Circuit

TCO

Auto

Beam

Limit

Vertical Blanking,

Brightness Control

- 157V

40V

300V

600V

15V

D/D Feed Back

12V

MICOM

(IC401)

SCL / SDA

H/V Sync,

PWM Control

15V

5V

15V

80V

15V

50V

DY CDT

Heater ( 6.3V )

I

2

C

I

2

C

I

2

C

H/V

Sync

G

1

Screen

Dynamic Focus

Static Focus

H.V

R/G/B

Drive/Contrast

Cut-Off

H-DRV

B-DRV

In

Out

B+

15V

TILT

COIL

DEGAUSSING

COIL

I

2

C

Vout 1

Vout 2

105V

40V

15V

DESCRIPTION OF BLOCK DIAGRAM

- 12 -

1. Line Filter & Associated Circuit.

This is used for suppressing noise of power input line
flowing into the monitor and/or some noise generated in
this monitor flowing out through the power input line.
That is to say, this circuit prevents interference between
the monitor and other electric appliances.

2. Degauss Circuit & Coil.

The degauss circuit consists of the degaussing coil, the
PTC(Positive Temperature Coefficient) thermistor(TH901),
and the relay(RL901). This circuit eliminates abnormal
color of the screen automatically by degaussing the
shadow mask in the CRT during turning on the power
switch. When you need to degauss in using the monitor,
select DEGAUSS on the OSD menu.

3. SMPS(Switching Mode Power Supply).

This circuit is working of 90~264V AC(50/60Hz).
The operation procedure is as follows:

1) AC input voltage is rectified and smoothed by the
bridge diodes (D900) and the capacitor (C908).

2) The rectified voltage(DC) is applied to the primary
coil of the transformer(T901).

3) The control IC(IC901) generates switching pulse to
turn on and off the primary coil of the transformer
(T901) repeatedly.

4) Depending on turn ratio of the transformer, the
secondary voltages appear at the secondary coils of
the transformer(T901).

5) These secondary voltages are rectified by each
diode(D941, D942, D951, D961, D962, D971) and
operate other circuit. (horizontal and vertical deflection,
video amplifier, ...etc.)

4. X-ray Protection.

I

f the high voltage of the FBT reaches up to 29kV (abnormal
state), Q807 operates and IC401(MICOM) pin 41 come to
low level. Then MICOM control IC701 (Deflection controller)
to stop Horizontal drive pulse and stop Horizontal Deflection.

5. Micom(Microprocessor) Circuit.

The operating procedure of Micom(Microprocessor) and its
associated circuit is as follows:

1) H and V sync signal is supplied from the signal cable.

2) The Micom(IC401) distinguishes polarity and
frequency of H and V sync.

3) The Micom sets operating mode and offers the
controlled data. (H-size, H-position, V-size, ... etc.)

4) The controlled data of each mode is stored in itself.

5) User can adjust screen condition by each OSD
function. The data of the adjusted condition is stored
in EEPROM(IC402).

6. Horizontal and Vertical Oscillation.

This circuit generates the horizontal pulse and the vertical
pulse by taking the H and V sync signal.
This circuit consists of the TDA4841(IC701) and the
associated circuit.

7. D/D(DC to DC) Converter.

This circuit supplies DC voltage to the horizontal deflection
output circuit by increasing DC 50V which is the
secondary voltage of the SMPS in accordance with the
input horizontal sync signal.

8. Horizontal Deflection Output Circuit.

This circuit makes the horizontal deflection by supplying
the saw-tooth current to the horizontal deflection yoke.

9. High Voltage Output & FBT(Flyback Transformer).

The high voltage output circuit is used for generating pulse
to the primary coil of the FBT(Flyback Transformer
(T701)). A boosted voltage(about 25.5kV) appears at the
secondary of the FBT and it is supplied to the anode,
focus, and screen voltage of the CRT.

10. H-Linearity Correction Circuit.

This circuit corrects the horizontal linearity for each
horizontal sync frequency.

11. Vertical Output Circuit.

This circuit inputs the vertical ramp ware from the
IC701(TDA4841) to the IC601(TDA4866) and amplifies,
supplies the saw-tooth current to the vertical deflection
yoke(V-DY).

12. Dynamic Focus Output Circuit.

This circuit amplifies the focus output ware of
IC701(TDA4841) pin 32 at the Q710 circuit, and then
superpositioning with H signal of T702, supplies it to the
FBT(T701). Therefore this circuit maintains constant focus
on center and corners in the screen.

13. H& V Blanking and Brightness Control.

Blanking circuit eliminates retrace line by supplying
negative pulse to the G1 of the CRT. And Brightness
circuit is used for control of the screen brightness by
changing DC level of the G1.

14. Image Rotation (Tilt) Circuit.

This circuit corrects the tilt of the screen by supplying the
image rotation signal to the tilt coil which is attached near
the deflection yoke of the CRT.