LG (CA-109) 701B CS778G 177V Schematic

COLOR MONIT OR

SER VICE MANUAL

CAUTION

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

MENU SELECT

MODEL: 177V

CHASSIS NO. : CA-109

F ACTORY MODEL: CS778G

1. PICTURE TUBE

Size : 17 inch
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 : 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 ~ 72 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

WIRING DIAGRAM ................................................. 6

DISASSEMBLY ....................................................... 7

BLOCK DIAGRAM ................................................... 8

DESCRIPTION OF BLOCK DIAGRAM.....................9

ADJUSTMENT ....................................................... 11

TROUBLESHOOTING GUIDE .............................. 13

EXPLODED VIEW...................................................23

REPLACEMENT PARTS LIST ............................... 25

PIN CONFIGURATION........................................... 30

SCHEMATIC DIAGRAM......................................... 32

PRINTED CIRCUIT BOARD................................... 34

SPECIFICATIONS

MODE

MAX

NORMAL (ON)

STAND-BY

SUSPEND

OFF

POWER CONSUMPTION

85 W

74 W
less than 8 W
less than 8 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 manufacturer 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

—

31.469

31.778

25.422

6.356

3.813

1.907

0.636

—

59.9

16.683

15.253

1.430

0.064

1.049

0.318

640

x

480

60Hz

Yes

MODE 1

—

31.472

31.774

25.419

6.355

3.813

1.906

0.635
+

70.1

14.267

12.710

1.557

0.064

1.080

0.413

720

x

400

70Hz

Yes

MODE 3

—

37.50

26.667

20.317

6.349

2.032

3.810

0.508

—

75.0

13.333

12.800

0.533

0.080

0.427

0.027

640

x

480

75Hz

Yes

MODE 4

—

43.269

23.111

17.778

5.333

1.556

2.222

1.556

—

85.0

11.764

11.093

0.670

0.069

0.578

0.023

640

x

480

85Hz

Yes

MODE 5

+

46.875

21.333

16.162

5.172

1.616

3.232

0.323
+

75.0

13.333

12.800

0.533

0.064

0.448

0.021

800

x

600

75Hz

Yes

MODE 6

+

53.674

18.631

14.222

4.409

1.138

2.702

0.569
+

85.061

11.756

11.179

0.578

0.056

0.503

0.019

800

x

600

85Hz

Yes

MODE 7

+

60.023

16.660

13.003

3.657

1.219

2.235

0.203
+

75.0

13.328

12.795

0.533

0.050

0.466

0.017

1024

x

768

75Hz

Yes

MODE 8

+

68.677

14.561

10.836

3.725

1.016

2.201

0.508
+

84.997

11.765

11.183

0.582

0.044

0.524

0.015

1024

x

768

85Hz

Yes

MODE 9

+

63.981

15.630

11.852

3.777

1.037

2.296

0.444
+

60.02

16.661

16.005

0.657

0.047

0.594

0.016

1280

x

1024

60Hz

Yes

MODE 10

—

50.6

19.752

15.802

3.950

1.580

1.975

0.395

—

100.1

9.995

9.481

0.514

0.059

0.435

0.020

640

x

480

100Hz

Yes

MODE 11

+

63.0

15.876

11.848

4.028

1.185

2.370

0.474
+

99.5

10.05

9.526

0.524

0.048

0.460

0.016

800

x

600

100Hz

Yes

MARK

E
A
B
D

F
C

E
A
B
D
F
C

Sync Polarity

Frequency

Total Period

Video Active Time

Blanking Time

Sync Duration

Back Porch

Front Porch

Sync Polarity

Frequency

Total Period

Video Active Time

Blanking Time

Sync Duration

Back Porch

Front Porch

FACTORY PRESET MODE

<< Dot Clock (MHz), Horizontal Frequency (kHz), Vertical Frequency (Hz), Horizontal etc... (µs), Vertical etc... (ms) >>

- 5 -

OPERATING INSTRUCTIONS

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 amber,
and if abnormal or damaging circuit turns out amber 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

WIRING DIAGRAM

- 6 -

P501

P201

P405

P301

P302

G2

P702

P701

T1

P402

P902

S

+

S

Signal

Cable

AC

Socket

FBT

- 7 -

DISASSEMBLY

Tip Spec.

A(Width) : 5.0~15.0mm
B(Depth) : 0.6~0.9mm
C(Height) : 12.0mm

1. TILT/SWIVEL & BACK COVER REMOVAL

1) Set the monitor face downward.

2) Pull 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.

2. TOTAL CHASSIS ASSEMBLY REMOVAL

1) Set the monitor face downward.

2) Pressing the latch (a), Main Chassis
by pushing it upward.

(a)

(a’)

CDT

Please be careful, not to cut pattern.

Back Cover

(c)

Cabinet

(a)

C

Tip

B

A

(b)

1

3

2

3

2

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

Voltage

Regulating

Circuit

80V
50V

15V

6.3V

TILT
Control
Circuit

6.3V

15V

E2PROM
(IC402)

H / V POSITION

BRIGHTNESS
CONTRAST

H / V SIZE
SPCC
TRAPEZOID
PIN BALANCE
PARALLELOGRAM
ROTATION
RECALL
DEGAUSS
COLOR CURVE
MOIRE
LANGUAGE
RESET
VIDEO LEVEL
OSD TIME

5V

OSD IC
(IC301)

MTV038-15

H-Sync Sig
V-Sync Sig

I2C DATA(SDA)
I2C CLOCK(SCL)

VIDEO

LM1269

PRE-AMP
(IC302)

Signal
Cable

R
G
B

VIDEO

LM2467

LM2480

CUT OFF IC
(IC304)

MAIN AMP
(IC303)

5V

5V

H/V Sync Processor

( IC701 )

TDA4857

V-OUT

( IC601)

TDA4866

H-OUT

( Q706)

H-Linearity

Correction

DC/DC Converter

X-RAY

Protection

Circuit

FBT

( T701 )

Dynamic

Focus

Circuit

Auto
Beam
Limit

Vertical Blanking,

Brightness Control

- 160V

40V

400V

STEP UP

15V

D/D Feed Back

15V

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

I2C

H/V

Sync

G
1

Screen(G2)

Dynamic Focus

Static Focus

H.V

R/G/B

Drive/Contrast

Cut-Off

H-DRV

B-DRV

B+

15V

TILT

COIL

DEGAUSSING

COIL

I2C

Vout 1
Vout 2

DESCRIPTION OF BLOCK DIAGRAM

- 9 -

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. Display Power Management Circuit.

This circuit control power consumption of the monitor by
detecting H and V sync signal. There are stand-by and
suspend mode. When no horizontal or vertical sync signal
input, the circuit consists of Q941 and Q951 becomes stand­by or suspend mode. It’s power consumption is below 8W.

5. X-ray Protection.

If the high voltage of the FBT reaches up to 29kV (abnormal
state), IC401(MICOM) pin 35 Sensing from FBT directly.
Then MICOM control IC701 (Deflection controller) to stop
Horizontal drive pulse and stop Horizontal Deflection.

6. 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).

7. Horizontal and Vertical Synchronous Processor.

This circuit generates the horizontal drive pulse and the
vertical drive pulse by taking sync-signal from the Signal­Cable. This circuit consists of the TDA4857(IC701) and
the associated circuit.

8. 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.

9. Side-Pincushion & Trapezoid Correction Cirucit.

This circuit improves the side-pincushion and the
trapezoid distortion of the screen by mixing parabola and
saw-tooth wave to output of the horizontal deflection D/D
converter which is used for the supply voltage(B + ) of the
deflection circuit.

10. Horizontal Deflection Output Circuit.

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

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

The high voltage output circuit is used for generating pulse
wave to the primary coil of the FBT(Flyback Transformer) .
A boosted voltage(about 26KV) appears at the secondary
of the FBT and it is supplied to the anode of the CDT. And
there are another output voltages such as the dynamic
focus and the screen voltage(G2).

12. H-Linearity Correction Circuit.

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

13. Vertical Output Circuit.

This circuit takes the vertical ramp wave from the
TDA4857(IC701) and performs the vertical deflection by
supplying the saw-tooth current from the TDA4866(IC601)
to the vertical deflection yoke.

14. Dynamic Focus Output Circuit.

This circuit takes the horizontal and the vertical parabola
waves from the TDA4857(IC701) and amplifies it to
maintain constant focus on center and corners in the
screen.

- 10 -

15. 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.

16. 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.

17. Moire Rdduction Circuit

This circuit reduce interference between the periodical
display pattern and the CDT’s mask.
The positions of every other one dot video signal
beams(red, green, and blue beam) are shifted finely, thus
reducing interference.

18. OSD Circuit

This circuit is used for performing the OSD(On-Screen­Display) function.
When a user selects the OSD Select/Adjustment control,
the adjustment status displays on the screen.

19. Video Pre-Amp Circuit.

This circuit amplifies the analog video signal from 0-0.7V
to 0-4V. It is operated by taking the clamp, R, G, B drive
and contrast signal from the Micom(IC401).

20. Video Output Amp Circuit.

This circuit amplifies the video signal which comes from
the video pre-amp circuit and amplified it to applied the
CRT cathode.