Samtron SC-726GXL Service Manual

COLOR MONITOR

SC-726GXL

-. -

’

SERWCEManua”

1. Precautions

2. Reference Information

3. Product Specifications

4. User Controls

5. Disassembly & Reassembly

6. Alignments & Adjustments

7. Troubleshooting

8. Exploded View & Parts List

9. Servicing Diagrams 9-l. Block Diagram 9-2. Wiring Diagram

9-3. PCB Layout and Electrical Parts List 9-4. Schematic Diagram

1 Precautions

Follow these safety, servicing and ESD precautions to prevent damage and to protect against potential hazards such as electrical shock and X-rays.

l-1

Safety Precautions

l-l-l Warnings

For continued safety, do not attempt to modify the circuit board.

Disconnect the AC power before servicing. When the chassis is operating, semiconductor

heat sinks are potential shock hazards.

l-l-2

Servicing the High Voltage System and Picture Tube

When servicing the high voltage system, remove the static charge by connecting a

10k

ohm resistor in series with an insulated wire (such as a test probe) between the chassis and the anode lead. (Disconnect the AC line cord from the AC outlet.)

Do not lift the picture tube by the neck.

Handle the picture tube only when wearing shatterproof goggles and after completely discharging the high voltage anode.

l-l-3 X-Rays and High Voltage Limits

Keep the high voltage below the specified maximum level. Be sure all service personnel are aware of the procedures and instructions covering X-rays. The only potential source of X-ray in current

solid state display monitors is the tube. However, the picture tube does not emit measurable X-ray radiation if the high voltage is as specified in the fire and shock hazard instruction. Only when high voltage is excessive are X-rays capable of penetrating the shell of the picture tube, including the lead in glass material.

It is essential that service technicians have an accurate high voltage meter available at all times. Check the calibration of this meter periodically.

High voltage should always be kept at the rated value, no higher. Operation at high voltages may cause failure of the picture tube or high voltage circuitry and, also under certain conditions, may produce X-rays in excess of acceptable levels.

When the high voltage regulator is operating properly there is no possibility of an X-ray problem. Test the brightness and use a meter to monitor the high voltage each time a color monitor comes in for service. Make sure the high voltage does not exceed its specified value and that it is regulating correctly.

The picture tube is especially designed to prohibit X-ray emissions. To ensure continued X-ray protection, replace the picture tube only with one that is the same or equivalent type as

the original. Carefully reinstall the picture tube shields and mounting hardware; these also provide X-ray protection.

When troubleshooting a monitor with excessively high voltage, avoid being unnecessarily close to the monitor. Do not operate the monitor longer than is necessary to locate the cause of excessive voltage.

l-l-4 Fire and Shock Hazard

Before returning the monitor to the user, perform the following safety checks:

Inspect each lead dress to make certain that the leads are not pinched or that hardware is not lodged between the chassis and other metal parts in the monitor.

Inspect all protective devices such as nonmetallic control knobs, insulating materials, cabinet backs, adjustment and compartment cover or shields, isolation resistor-capacitor networks, mechanical insulators, etc.

SC-726GXL

l-l

1 Precautions

AC Voltmeter

To Exposed

To Known

Metal

Par%

Earth Ground

Use a SSVM or VOM with 1000 ohms per-volt or higher sensitivity to measure the AC voltage drop across the resistor (see Figure l-1).

Connect the resistor to an exposed metal part having a return path to the chassis (metal cabinet, screw heads, knobs, shafts, escutcheon, etc.) and measure the AC voltage drop across the resistor.

Any reading of 5.25 Volt RMS (this corresponds to 3.5 milliampere AC) or more is excessive and indicates a potential shock hazard. Correct the shock hazard before returning the monitor to the user.

l-l-5 Product Safety Notices

Some electrical and mechanical parts have special safety-related characteristics which are often not evident from visual inspection. The protection they give may not be obtained by replacing them with components rated for higher voltage, wattage, etc. Parts that have special safety characteristics are identified by A on schematics and parts lists. A substitute replacement that does not have the same safety characteristics as the recommended replacement part might create shock, fire and / or other hazards. Product safety is under review continuously and new instructions are issued whenever appropriate.

Figure1

-1.

leakage Current Test Circuit

To be sure that no shock hazard exists, check

for leakage current in the following manner:

Plug the AC line cord directly into a 120 Volt AC outlet. (Do not use an isolation transformer for this test)

Using two clip leads, connect a

1.5k

ohm,

10 watt resistor paralleled by a 0.15

capacitor in series with an exposed metal cabinet part and a known earth ground, such as an electrical conduit or electrical ground connected to an earth ground.

1-2

SC-726GXL

. ,-., - ,

,* :. . ,

1 Precautions

1-2 Servicing Precautions

Warning: AI-I electrolytic capacitor installed with the wrong polarity might explode.

Caution: Before servicing instruments covered by this service manual and its supplements, read and follow the Safety Precautions section of this manual.

Note: If unforeseen circumstances create conflict between the following servicing precautions and any of the safety precautions, always follow the safety precautions.

1-2-1 General Servicing Precautions

Always connect a test instrument’s ground

1.2.Servicing precautions are printed on the cabinet. Follow them.

Always unplug the unit’s AC power cord from the AC power source before attempting to: (a) remove or reinstall any component or assembly, (b) disconnect an electrical plug or connector, (c) connect a test component in parallel with an electrolytic capacitor.

lead to the instrument chassis ground before connecting the positive lead; always remove the instrument’s ground lead last.

Some components are raised above the printed circuit board for safety. An insulation tube or tape is sometimes used. The internal wiring is sometimes clamped to prevent contact with thermally hot components. Reinstall all such elements to their original position.

After servicing, always check that the screws, components and wiring have been correctly reinstalled. Make sure that the portion around the serviced part has not been damaged.

Check the insulation between the blades of the AC plug and accessible conductive parts (examples: metal panels, input terminals and earphone jacks).

Insulation Checking Procedure: Disconnect the power cord from the AC source and turn the

power switch ON. Connect an insulation

resistance meter (500 V) to the blades of the

AC plug. The insulation resistance between each blade

of the AC plug and accessible conductive parts (see above) should be greater than 1

megohm.

Never defeat any of the B+ voltage interlocks. Do not apply AC power to the unit (or any of its assemblies) unless all solid-state heat sinks are correctly installed.

SC-726GXL

l-3

1 Precautions

l-3 Electrostatically Sensitive Devices (ESD) Precautions

Some semiconductor (solid state) devices can be easily damaged by static electricity. Such components commonly are called Electrostatically Sensitive Devices (ESD). Examples of typical ESD devices are integrated circuits and some field-effect transistors. The following techniques will reduce the incidence of component damage caused by static electricity.

Immediately before handling any semiconductor components or assemblies, drain the electrostatic charge from your body by touching a known earth ground. Alternatively, wear a

dischar,tig

wrist-strap device. To avoid a shock hazard, be sure to remove the wrist strap before applying power to the monitor.

After removing an ESD-equipped assembly, place it on a conductive surface such as aluminum foil to prevent accumulation of electrostatic charge.

Do not use freon-propelled chemicals. These can generate electrical charges sufficient to damage

ESDs.

Use only a grounded-tip soldering iron to solder or desolder

ESDs.

Minimize body motions when handling unpackaged replacement

ESDs.

Motions such as brushing clothes together, or lifting your foot from a carpeted floor can generate enough static electricity to damage an ESD.

marks parts for

ESDs

on schematic

diagrams and electrical parts list.

Use only an anti-static solder removal device. Some solder removal devices not classified as “antistatic” can generate electrical charges sufficient to damage

ESDs.

Do not remove a replacement ESD from its protective package until you are ready to install it. Most replacement

ESDs

are packaged with leads that are electrically shorted together by conductive foam, aluminum foil or other conductive materials.

Immediately before removing the protective material from the leads of a replacement ESD, touch the protective material to the chassis or circuit assembly into which the device will be installed.

Caution: Be sure no power is applied to the

chassis or circuit and observe all other safety precautions.

1-4

SC-726GXL

- =__

-’

Reference Information

2-l

Eming

Chart

This

section of the service manual describes the timing that the computer industry recognizes as standard

for computer-generated video signals.

Table 2-l. Timing Chart

fH (kHz)

psec

fv (Hz)

msec

msec R msec

msec

Clock Frequency

@J-W

Polarity

H.Sync

V. Sync

Remark

IBM

VGAzf70

720x400

VGA3l60 Hz

640x480

640/Z

640x480

31.469

37.500

31.777

31.778

26.667

3.813

2.032

1.907

3.810

25.422

20.317

0.636

0.508

70.087

59.940

75.000

14.268

16.683

13.333

0.064

0.080

1.080

i ,048

0.427

12.711

15.253

12.800

0.413

0.318

0.027

28.322

25.175

31.500

Positive

Negative

Separate

Negative Negative

Separate

Negative Negative

Separate

Separate Sync

VESA

aoop5

800x600

46.875

21.333

1.616

3.232

16.162

0.323

75.000

13.333

0.064

0.448

12.800

0.021

49.500

Positive

Separate

1024/60

1024x768

1024P5 Hz

1024x768

48.363

60 023

20.677

6.660

2.092

1.219

2.462

2.235

15.754 13.003

0.369

0.203

60.004 75.029

16.666

13.328

0.124 0.050

0.600 0.466

15.880 12.795

0.062 0.017

65.000 78.750

Negative Negative

Separate

Positive Positive

Separate

A : Line time total

6 :

Sync width C : Back porch

0 :

Active time E : Front porch

0 : Frame time total P : Sync width Q : Back porch

R :

Active time

S : Front porch

SC-726GXL

2-l

2 Reference Information

Mode

Timing

fH (kHz)

usec

psec

C psec

Cl usec

usec

fv (Hz)

0 msec

msec Cl msec R msec

msec

Clock

Frequency

(MHz)

Polarity

HSync V.Syrlc

Remark

VESA

128OP5

1280x1024

79.976

12.504

1.067

1.837

9.481

0.119

75.025

13.329

0.038

0.475

12.804

0.013

Table 2-l.

Timi

SIGMA

800/120

800x600

76.923

13.000

1.100

1.400

10.000

0.500

120.192

8.320

0.195

0.247

7.800

0.078

135.000

Positive Positive

Separate

80.000

Negative Negative

Separate

Chart Continued

Apple Mac.

WI75

832x624

49.726

20.110

1.117

3.910

14.524

0.559

74.551

13.414

0.060

0.784

12.549

0.020

57.284

Negative Negative

Separate

1152P5

1152x870

68.681

14.560

1.280

1.440

11.520

0.320

75.062

13.322

0.044

0.568

12.667

0.044

100.000

Negative Negative

Composite

ISync-on-green+Composlte)

SUN

lWJ76

1152x900

71.713

13.945

0.909

1.970

10.913

0.152

76.047

13.150

0.112

0.460

12.550

0.028

105.560

Negative/Positive Negative/Positive

Separate

A : Line time total

B : Sync width

C : Back porch

D : Active time E : Front porch

R :

Active time

0 : Frame time total S : Front porch

P : Sync width

Cl :

Back porch

2 Reference Information

2-2 Semiconductor lead Identification

D109,D110,0111.D301,D303 D310.D401.D402.D404,D414 D417.0515, D602,D606,0802 D803,D804,DBl,DBZ,DB3,

DG3, DG4, DG5, DG6, DG7,

DAl,

ZD101,20102.20103.

D403 D617,0618.D619,

SC726GXL

2-3

2 Reference Information

2-2 Semiconductor Lead Identification

2-4

SC-726GXL

3 Product Specifications

3-1 Specifications

Picture Tube:

Scanning Frequency

Display Colors Analog input

Maximum Resolution

Input Video Signal

Input Sync Signal

Maximum Pixel Clock

Active Display

Input Voltage

Power Consumption

Dimensions Unit

(HxWxD)

Carton (HxWxD)

Weight

Environmental Considerations

CRT Code No.

17-Inch

(43 cm):

15.7-Inch

(40 cm) Visual, Full square/flat face tube, 90” deflection,

0.26 mm Dot pitch, Semi-tint, Non-glare, Antistatic silica coating, lnvar shadow mask

Horizontal : 30

kHz

to 85

kHz

(Automatic)

Vertical

50 Hz to 120 Hz (Automatic)

Unlimited Colors

Horizontal : 1280 Dots Vertical : 1024 Lines

Analog 0.714 Vp-p Positive at 75 Q Terminated

Separate Sync : TTL level Positive/Negative Sync-on-Green: Composite Sync 0.286 Vp-p ? 5 %/Negative (Video on Vp-p positive) Composite Sync : TTL level Positive/Negative

135 MHz

Horizontal 306 mm + 3 mm

(4:3

ratio) / 287.5 mm k 3 mm

(54

Ratio)

Vertical : 230

mm_+3

AC 90-l 32 / 198-264 Volt, 60 Hz/50 Hz+3 Hz

120 Watt (Max)

16.5 x 16.9 x 17.3 Inches (420 x 428 x 439 mm)

21.2 x 21.5 x 21.9 Inches (538 x 545 x 554 mm)

Net/Gross: 41.9 Lbs (19 kg) / 48.5 Lbs (22 kg)

Operating Temperature : 32°F to 104°F

(0’

C to 40” C)

Humidity : 10 % to 80 %

Storage Temperature

-4°F to 113°F (-20” c to 45”

Humidity : 5 % to 95 %

897

25013OAA

(Hitachi) : ASC Coating

BH03-10008A (Samsung): ASC Coating

l SC-726GXL complies with SWEDAC (MPRII) recommendations for reduced electrostatic fields. l Designs and specifications are subject to change without prior notice.

3 Product Specifications

3-2 Dimensions

SC-726GXL

428 mm

___----

.-__

,_------~_

439 mm

451“- -f- 45’

Swivel angle

3-2

SC-726GXL

3 Product Specifications

3-3 Pin Assignments

Red

Green

Blue

GND

DDC Return

GND-R

GND-G

GND-B

Reserved

GND-Sync/Self-Raster

GND

DDC Data

H-Sync

V-Sync

DDC Clock

15-Pin Signal Cable Corldectm (Figure 3-1)

Separate

Figure 3-l. Male

Type

Composite

Red Green Blue GND DDC Return GND-R GND-G GND-B Reserved GND-Sync/Self-Raster GND DDC Data H/V-Sync Not Used DDC Clock

BNC Connectors

BNC connectors are used with coaxial cable for improved signal transmission. Better signal transmission becomes critical at high frequencies such as those required for

1280X1024

resolution.Most

video boards that operate at 1280X1024 resolution

recommend using coaxial cable with BNC connectors.The

5BNC

connectors on the rear of

the

monitor can accept Red, Green, and Blue video. Composite sync can be applied separately, or combined with the Green video signal (commonly

referred to as “composite sync-on-green”). If composite sync-on-green is used, then only 3 of the 5 BNC connectors are used. The connectors are

labeled accordingly.

Sync

Green

Red

GreentH/V

Sync Blue GND DDC Return GND-R

GND-G

GND-B Reserved

GND-Sync/Self-Raster

GND DDC Data Not Used Not Used DDC Clock

Cable Adapter (Figure

3-2)

Macintosh

GND-R Red H/V Sync Sense 0 Green

GND-G Sense 1 Reserved Blue Sense 2

GNO

V-Sync GND-B GND H-Sync

Figure 3-2. Male Type

Signals

Figure 3-3. BNC Signal Input Type

SC-726GXL

3-3

_. .

* --_.

.’ ._

4 User Controls

4-l Front View and

Cotitrols

4-l-l SC-726GXL Front View

Figure

4-l.

SC-726GXL Front Control Panel

User Adjustments

Directions for making User Adjustments are the

same as those given in Chapter 6, Alignments and Adjustments, under the directions for “Without microcomputer control jig.”

_. . .

4-l-2 SC-726GXL Front Control Panel

.ocation

Symbol

633

” /

On Screen Display

Description

Power Button (Push)

Power Indicator LED (Dual

Color1

Contrast Control

Brightness Control

Adjustment Controls

Degauss Button

BNC/D-SUB,

Recall Button Push once: Recall Push twice:

BNC/D-SUB

Color Temperature Control / Color Control

(Hue/Saturation)/Sync Select

Push Once: Color Temperature Control Push twice:Color Control (Hue/Saturation) Push three times: Sync Select

G/D (Geometric Distortion) Push once: Pincushion /Trapezoid Push twice: Parallelogram /Tilt

Size and Information Push once: Size (Horizontal /Vertical) Push twice: Information

Position and Modes Push once: Position (Horizontal /Vertical)

Push twice: User and Preset Modes

The monitor features an On Screen Display (OSD) that shows information about the display settings. The OSD appears on the screen when you select a function button. The OSD shows the name, range and current setting of the control function. In addition, the OSD shows the current input signal frequency and the list of user and factory preset timings. The OSD remains active for approximately 1C seconds after completion of any

adjustment.

SC-726GXL

4-1

4 User Controls

Note

Note 2

This monitor requires a cable adapter for use with a

R/iacintosh

computer. The MacMaster Cable Adapter supports all monitors

an?I

all Macintosh, Centris,

Quadra, Duo Dock, and Power Macintosh computers. If you do not already have a

cabIe

adapter, check with your computer

dealer. The monitor automatically returns to the

normal operation state when horizontal and vertical sync returns. This occurs when you move your mouse or press a key on your keyboard.

This monitor is EPA Energy Star compliant and

NLTTEK

compliant when used with a computer equipped with VESA DPMS function. If your computer system cannot support a display power management function, you may purchase an optional DPMS software program to take advantage of the power saving function. Please contact

Samsung,

or your

dealer, for more information. For Energy conservation, turn your

monitor OFF when the monitor is not needed, or when leaving it unattended for long periods.

Table 4-l Display Power Management Signaling

(DPMS)

Standard

4-2

SC-726GXL

5 Disassembly and Reassembly

This section of the service manual describes the disassembly and reassembly procedures for SC-726GXL monitor.

WARNING: This monitor contains electrostatically sensitive devices. Use caution when handling any components.

5-l Disassembly

5-l-l Removing the Cabinet

1. With a pad underneath it, stand the monitor on

its front with the screen facing downward and the base closest to you. Make sure nothing will damage the screen.

2. Working from the back of the monitor, remove

the six

screws.

:: ::::::

,r ._....

.-- . . . . . .

-. . . ...*

Figure 5-1.

3. Tilt the cabinet away to release the three tabs and pull it up and away from the monitor.

4. Remove the two screws from the cabinet bottom. Lift the bottom off and away from the monitor.

Fig

5-l-2 Removing the Video PCB

Remove the four connectors:

Sync Power

Video out Color controller

Remove the three screws (A) holding the Video PCB Ass’y onto the main PCB Ass’y and slide it off.

Remove the six screws on the Video PCB Shield and lift the top off.

Remove the one screw holding the Video PCB Shield bottom and left the PCB out.

Set Video PCB on a smooth, level surface which is protected from static electricity.

Figure

5-2.

5. Remove the 14 screws from around the metal shielding. Lift the shielding up and away from the CRT.

A-

Figure

5-4.

SC-726GXL

5-1

-_’ .

5 Disassembly and Reassembly

5-l-3 Removing the Main PCB

1. If you have not already done so, remove the

Video PCB.

2. Remove the CRT PCB.

3. Remove the two screws holding the main PCB Ass’y to the front cover.

Pull Off

Figure 5-5.

Remove the accessible connectors:

%Ound

wire

Degaussing coil Anode cap

5. Lift the Main PCB Ass’y up slightly and tilt it away from the CRT so that you can reach and remove the following connectors:

Horizontal deflection yoke Vertical deflection yoke

Controller Function key

Figure 5-6.

6. Pull the Main PCB Ass’y away from the CRT.

7. Remove the eight screws holding the main PCB

in the PCB Bracket, remove the power shaft and lift the Main PCB out.

Set main PCB on a smooth, level surface which is protected from static electricity.

Figure 5-7

5-l-4 Removing the CRT

Caution: Do not touch the Anode

If you have not already done so, remove the Main PCB.

Remove the eight screws securing the CRT Bracket Assembly.

Release the grounding wire clips from the grounding prongs on the CRT Bracket Ass’y.

Lift the CRT Bracket Ass’y up and away from

the CRT. The CRT Bracket Ass’y includes the bracket, degaussmg coil and tilt coil.

Remove the screw at each of the four comers of the CRT. This releases the CRT and the CRT Ground Ass’y. Lift the CRT tube (do not lift by

(

the tube neck) out of the Front Cover Assembly. Remove the CRT Ground Ass’y.

** :_=--.-(

Figure 5-8.

5 Disassembly and Reassembly

5-2 Reassembly

With the CRT facing

downw-ard

on a protective pad, use the steps that follow to reassemble the monitor.

5-Z-l Replacing the CRT

1. With the front cover assembly lying face down

on a protective pad, position the CRT so that the corner metal tabs fit properly in the Front Cover.

2. Position the CRT Ground Ass’y around the CRT and secure it and the CRT at each of the four corners with the CRT screws. Make sure the grounding wire clips are accessible.

3. Position the CRT Bracket Ass’y around the CRT

and replace the eight screws. Attach the grounding wire clips onto the grounding

prongs on the CRT Bracket Ass’y.

5-2-2 Replacing the Video PCB

1. Place the Video PCB in the Video Shield bottom

and replace the one screw that holds it in place.

2. Position the Video Shield top on the bottom and replace the six screws.

3. Slide the Video PCB Ass’y onto the Main PCB

Ass’y and secure it with two screws.

4. Reconnect the four connectors:

Color controller Video out Power Sync

5-2-3 Replacing the Main PCB

1. Set the Main PCB in the PCB bracket and secure

it with eight screws.

2. Hold the Main PCB Ass’y close to the CRT as

shown in figure 5-7 and reconnect the following connectors:

Function key Controller Vertical deflection yoke

Horizontal deflection yoke

Anode cap

Degaussing coil Tilt control Ground coil

3. ‘Replace the CRT PCB

4. Position the Main PCB Ass’y on the front cover (see figure 5-5) and hold it secure with two screws.

5. If you have not already done so, replace the Video PCB.

5-2-4 Replacing the Cabinet

Position the metal shielding around the CRT. If so equipped, make sure the tabs are snapped

in place. Replace the 14 screws. See figure 5-3. Position the cabinet bottom and replace the two

screws (see figure 5-2).

Position the cabinet top making sure the three

tabs along the upper front edge are properly

snapped in place. Replace the six screws.

Set the monitor on its base and make sure that

the CRT screen was not scratched or otherwise

damaged.

6 Alignments and Adjustments

This section of the service manual explains how to control the linearity, raster, size, position, pincushion, parallelogram, trapezoid, and

pinbalance.

Additionally, this section describes how to use the micom control

jig to make the adjustments.

6-l

Adjustment Conditions

Caution: Changes made without the micom jig are saved only to the user mode settings. As such, the settings are not permanently

stored and may be inadvertently deleted by the user.

Direction

When servicing, always face the monitor toward

the East and, whenever possible, use magnetic field isolation such as a helmholtz field around the monitor.

Caution: Other electrical equipment may cause external magnetic fields.

During servicing, use an external degaussing coil to limit magnetic build up, If an external

degaussmg coil is not available, use the internal

degaussing circuit, but not more than once per minute.

After finishing all adjustments, test the monitor in all directions. If, for example, the monitor does not meet adjustment specifications when facing in a northerly direction, face the monitor eastward again and readjust the monitor to the smallest error possible within a reasonable time limit. Test the unit again in all directions. If the monitor again fails to meet specifications in a non-easterly direction, contact your region’s main service center for possible CRT replacement.

Testing and Burn-in Mode

For testing and bum-in, remove the signal cable from the monitor. Power on the monitor and warm it up. Use the bum-in mode to age the monitor.

Power Supply Voltage

AC 90-132 / 198-264 Volt

(60/50 Hz&3

High Voltage Control

Adjust

VR501

to 26 kVr0.2

kV.

Warm-Up Time The display must be on for 30 minutes before

starting alignment. Warm-up time is especially critical in color temperature and white balance adjustments.

Signal

Video analog 0.714 Vp-p positive at 75 ohm terminated.

Sync: Separate/composite

(TTL

level negative/positive).

Sync-on-Green: Composite sync 0.286 Vp-p negative

(Video 0.714 Vp-p positive).

Scanning Frequency

Horizontal

kHz-85 kHz

(Automatic).

Vertical

50 Hz-120 Hz (Automatic).

Unless otherwise specified, adjust to 1024x768 mode (H : 60

kHz,

V: 75 Hz) signals. Refer to

table 2-l on pages 2-l and 2-2.

6-2 Prepare Main PCB for Adjustment

+B 195V

Line Adjustment

No beam, Contrast: Minimum, Brightness: Minimum.

Adjust VR601 to DC

and GND.

High Voltage Adjustment No beam, Contrast: Minimum,

Brightness: Minimum Adjust

VR501

to 26

kVa.2 kV.

_. .

V+l

V at

Q406

heat sink

Center Raster

Adjust SW401 so that the back raster comes to the center when you apply a signal of 60

kHz/75

Hz.

‘ =*.

. . .i

SC-726GXL

6-l

6 Alignments and Adjustments

6-3 Using the Microcomputer Control Jig

LCD

PANEL _

Figure 6-I. Micom Control Jig Keypad

Notes: Changes made without the micom jig are saved

only to the user mode settings. As such, these setting are not permanently stored and may be inadvertently deleted by the user.

Selecting the monitor series and type:

Simultaneously press buttons 29 and 24 to select “M-Project” as the monitor series.

Press button 25 to select the monitor type. Hold down button 25 until you see

“M17H”

plus the OEM name for the monitor under test. For example, hold down button 25 until you see

“M17H”

if you are working on a “Dell 17.”

Table 6-l. Micom Control Jig Function Keys

General Control

Color Control

No.

Key Function

Key

Fllnction

Horizontal Position Right

R-Gain Increase

Horizontal

P&ion Left

R-Gain Decrease

Parallelogram Right

ACL Increase

Parallelogram Left

ACL Decrease

Mode

SUE

Color Save

Horizontal Size Increase

G-Gain Increase

Horizontal Size Decrease

G-Gain Decrease

Vertical Linearii Increase

Color CH-1 Standard Save

Vertical Linearii Decrease

Color CH-2 Standard Save

Standard Save

ACL Save

Vertical Position Up

B-Gain Increase

Vertical Position DOW

EGain

Decrease

Pinbalance Left

Function

(Don’t Use)

Pinbalance

Right

Functicn

(Don’t Use)

All Mode Save

No Function (Don’t Use)

Vertical Size Increase

R-Bias Increase

Vertical Size Decrease

R-Bias Decrease

Tilt

No Function (Don’t Use)

lilt

DOW

No Function (Don’t Use)

User Mode Delete

No Function (Don’t Use)

Barrel

G-Bias Increase

Pincushion

G-Bias Decrease

Hc<allinearih/lnaease

No Function (Don’t Use)

HokltiILineacmpeaease

No Function (Don’t Use)

Model Selection

No Function

(Don’t

Use)

Trapezoid Up

&Bias Increase

Trapezoid Down

B-Bias Decrease

No Function (Don’t Use)

Shift

Fution

(Don’t Use)

Manual/Auto Color

Control

t23

Color/General~ltoggle

Cobr/Genecal Gxtml @$e

t24

F-Pmje&M-Project

toggle

F-Project/M-Pmject

toggle

6-2

SC-726GXL

-. .

-4

6-3-l General Control

6-3-2 Color Control

Use general control to test and adjust the shape and size of the display.

Use

color control to test and adjust the color

coordinates the monitor displays.

Simultaneously press buttons 28 and 23 to toggle between General Control and Color Control. Select “General Control.”

Simultaneously press buttons 28 and 23 to

toggle between General Control and Color

Control. Select “Color Control.”

Standard Save: Press button 10 to do a memory data dump and load the standard picture data from the EPROM on the micom control jig.

Press button 8 (for 9300K setting) or 9 (for 6500K settings) to do a memory data dump and to load the standard picture color data from the micom control jig.

Note: This step is necessary only if the EPROM

on the control jig has more recent data than the

EPROM on the monitor PCB. Check for a

Service Bulletin or Service Manual

Supplement.

Optimize the standard timing mode (60

kHz /75

Hz) using the micom control jig as described on pages 6-3 through 6-5 of this manual.

Optimize the standard timing mode using the micom control jig as described on pages 6-6 and 6-7 of this manual.

After completing all standard timing mode adjustments, press button 15 to save the data for all modes. The monitor’s microprocessor

adjusts the other modes according to a

predefined formula.

Press button 5 to save the picture color data. Press button 10 to save ACL data.

Using a signal generator, scan the other timing modes and make adjustments as needed. Each time you make a change, press button number 5 to save the data.

When you are through, disconnect the micom control jig and proceed with other tests and adjustments.

6-4 Display Control Adjustments

Unless otherwise specified, adjust the

EXT-VR:

Contrast

Max. (Fully clockwise)

Brightness : Max. (Fully clockwise)

6-4-l Centering

Centering means to position the center point of the display in the middle of the display area. Horizontal size and position and vertical size and

position control the centering of the display. Adjust the horizontal size and vertical size to their

optimal settings: 306 mm (H) x 230 mm (V) Adjust the horizontal position and vertical

position to

3.0

mm of the center point of the screen. IA-BI <4.Omm.

IC-DI

<4.Omm.

-Display area

-Edge

of bezel

Figure 6-2. Centering

6-4-2 Horizontal Size Adjustment

With microcomputer control jig: Press the horizontal size up button (6) or

horizontal size down button (7) to adjust the horizontal size of the display pattern to 306 mm. (Tolerance: 10 mm.)

Without microcomputer control jig: After pushing the

siqe

button, push the ( b ) button or ( 4 ) button to adjust the horizontal size of the display pattern to 306 mm. (Tolerance

mm.)

-. -

6 Alignments and Adjustments

6-4-3 Vertical Size Adjustment

With microcomputer control jig: Press the vertical size increase button (16) or the

vertical size decrease button (17) to adjust the verb

ical

image or pattern to 230 mm. (Tolerance:

k3mm.)

Without microcomputer control jig: After pushing the size button, push the ( A )

button or ( V ) button to adjust the vertical size of the display pattern to 230 mm. (Tolerance: r3 mm.)

6-4-4 Horizontal Position Adjustment

With microcomputer control jig: Press the horizontal position right button (1) or the

horizontal position left button (2) to center the

image or test pattern on the raster.

Without microcomputer control jig: After pushing the position button, push the ( b

)

button (move right) or ( 4 ) button (move left) to

center the image or test pattern on the raster.

6-4-5 Vertical Position Adjustment

With microcomputer control jig: Press the vertical position up button (11) or

vertical position down button (12) to center the vertical image or pattern on the raster.

Without microcomputer control jig:

After pushing the position button, push the ( A

)

button (move up) or (V ) button (move down) to center the image or the test pattern on the raster.

6-4-6 Vertical Linearity Adjustment

Linearity affects the symmetry of images on the screen. Unless each row or column of blocks in a crosshatch pattern is of equal size, or within the tolerances shown in Tables 6-2 and 6-3, an image appears distorted, elongated or

squashed. To adjust the Vertical and Horizontal Linearity,

refer to Tables 6-2 and 6-3 for the tolerance range.

Table 6-2. Standard Mode Linearity: 60.023

kHz/75

Hz,

79.976 kHz/75 Hz

Factory Preset Timing

Modes

Standard Mode Each

block

(5%)

Difference

between

adjacent blocks

(4%)

8GUx6W75 Hz

Hortzontal

18.2 - 20.1

Horizontal:

Less than 0.8

1024x768/75

Vertical

18.2 - 20.1

Vertical: Less than 0.8

12EOx1024 / 75Hz

Horizontal : 17.1 - 18.9

Horizontal: Less than 0.7 mm

Vertical

: 18.2 - 20.1

Vertical

Less than 0.8

Table 6-3. Other Modes Linearity: VGA, 8514/A,

XGA, MAC, etc.

Supported Timing Modes

Screen Ratio

Each block (7%)

Olfference

between

adjacent blocks

(5%1

4:3

5.4

Horizontal

17.8 - 20.5

Horizontal:

less

than1 .O

Verwal

.178-205

Vertical

less

than1 .O

Horuontal

16 7 - 19.2

Horizontal

less

than

0.9 mm

Vertical

,178-Z

Verwai

less than 1 0 mm

With microcomputer control jig:

Press the vertical linearity increase button (8) or vertical linearity decrease button (9) to optimize the image or the test pattern.

Without microcomputer control jig: To activate the vertical linearity adjustment

function, push and hold in both the position and the size buttons for longer than three seconds, or until the power indicator LED changes from orange to green and back to orange. Use the right ( b ) and left (4 ) buttons to correct the vertical linearity.

6-4-7 Horizontal Linearity Adjustment

With microcomputer control jig: Press the horizontal linearity increase button (23)

or horizontal linearity decrease button (24) to optimize the image or the test pattern.

Without microcomputer control jig: After pushing G/D button once, push the

( v )

button or ( A ) button to make the image or

the test pattern rectangular.

IA-61 <

Zmm

IC-III <

Zmm

L A -4

r-7

r---l

L--.-L

Figure 6-3. Trapezoid

6-4

SC-726GXL

=__.!

I_.

6 Alignments and Adjustments

6-4-8 Pinbalance Adjustment

With microcomputer control jig:

Press the pinbalance left button (13) or pinbalance right button (14) to optimize the image or test pattern.

Without microcomputer control jig: To activate the pinbalance adjustment function,

push and hold in both the position and the size buttons for longer than three seconds, or until the power indicator LED changes from orange to

green and back to orange. Use the up ( b ) and down ( 4 ) buttons to correct the pinbalance distortion of one or both sides.

6-4-9 Parallelogram Adjustment

With microcomputer control jig: Press the parallelogram right button (3) or the

parallelogram left button (4) to make the image or test pattern rectangular.

Without microcomputer control jig:

After pushing G/D button twice, push

(F)

button

or (4 ) button to make the image or test pattern

rectangular.

k-----l

Zmm

Figure

6-4. Parallelogram

6-4-10 Side Pincushion Adjustment

With microcomputer control jig:

Press the barrel button (21) or the pincushion button (22) to straighten the sides of the test pattern or image.

Without microcomputer control jig: After pushing G/D button once, push

(b)

button

(4)

button to straighten the sides of the test

pattern or the image.

Cl I, I C2 I I2 mm, I Dl I, I D2 I

mm.

Figure 6-5.

Pinchshion

6-4-11 lilt Adjustment

Direction: Monitor MUST face to the East.

Use mechanical adjustment if correction needed is

p1.5

mm. With microcomputer control jig: Press the tilt up button (18) or the tilt down button

(19) to correct the tilt of the display. Without microcomputer control jig:

Push the G/D button twice to display the tilt OSD. Push either the tilt up ( A ) or down ( V ) button to display the tilt OSD.

Use the up ( A) and down

(

)

buttons again to

correct the tilt of the display.

CRT Tilt Adjustment

Mechanical Adjustment: Reassemble the CRT with fastening screws so that

the dimensions A, B and C, D are separately equal. If you are unable to correct the tilt, contact the

regional service center for CRT replacement.

Figure 6-6. CRT Tilt Adjustment

Degauss

No adjustments available for degaussing circuit.

The degaussing circuit can effectively function

only once per minute. If available, use an external

degaussing coil during servicing.

Warning: Don’t hold the degauss button down for

longer than 3 seconds. If you do, it resets all data in the user memory area. If this occurs, you must remake the user adjustments.

6-4-12 To Delete the User Mode Data

With microcomputer control jig: To delete the picture data from user’s modes, push

user’s mode delete button (20).

Without microcomputer control jig:

To delete the picture data from user’s modes, press

the degaussing button for 5 or more seconds.

6-4-13 Save the Data

With microcomput$r control jig:

To save the picture data for a mode, push the mode save button (5).

SC-726GXL

6-5

_. .

* =__

*. ._

6 Alignments and Adjustments

6-5 Color Adjustments

Note:To make color adjustmentsyoumusthave

one of the following configurations:

Micom Control Jig and Signal Generator. or

2. Micom Control Jig and Computer with

Samsung DM 200 software or

DisplayMate

for

Windows software from

Sonera

Technologies.

Before making adjustments check that the video

signals are as follows: Video : Analog 0.714 Vp-p (at 75 R terminated).

Sync

Synchronizing: Separate

TTL

level. Unless otherwise specified, use 1024x768 signal (60

kHz/75

Hz) for the

adjustments.

6-5-l Color Coordinates (Temperature)

Color temperature is a measure of the radiant

energy transmitted by a color. For computer

monitors, the color temperature refers to the

radiant energy transmitted by white. Color coordinates are the X and Y coordinates on the chromaticity diagram of wavelengths for the visible spectrum.

Table 6-4. Color Coordinates

Value

9300" K :

x=0.283+0.02,

=0.298~.02.

6500" K

: x

=0.313*0.02.

=0.3291tO.O2.

Conditions

Display Image: White flat field at the

center of display area.

Luminance

Min

: 5

ft-L, Max : 24 ft-L.

6-5-2 Luminance Uniformity

Luminance uniformity means that the luminance at the position of the lowest brightness must be more than 75% of the luminance at the area with

the highest brightness. Luminance is considered uniform only if the ratio of lowest to highest brightness is not less than

7.5:10.

Table 6-5. Computing Luminance Uniformity

Value

75 % (Min) Variation = + x 100

Conditions

Display Image : White flat field.

Luminance

Brightness cut off, Contrast Max.

A : Luminance at position of highest brightness. C : Luminance at position of lowest brightness.

6-5-3 Color Adjustments for 9300°K

- 1

6-5-3 (a) Adjustment of the Back Raster Color

(60

kHz/75

Hz, Back raster pattern)

1. Turn the contrast and the brightness controls fully clockwise (maximum condition).

2. Adjust the screen VR of the FBT so that the brightness of back raster is 0.5 to 0.7 ft-L (typically 0.6 ft-L).

3. Press button 8 to download the standard color data (channel 1) from the micom jig.

For 9300” K color adjustment: x =

0.283d.02,

y =

0.298rO.02.

For 6500” K color adjustments see section 6-5-4 “Color Adjustments for 6500” K.”

Use buttons 26 and 27 to set the “y” coordinate to

0.298Fo.02.

Use buttons 16 and 17 to set the “x”

coordinate to

0.283+3.02.

Note: If the above adjustments cannot be done to each coordinate, press button 21 to increase the green bias, or button 22 to decrease the green bias and repeat procedures 4 and 5.

After completing the adjustments, press

button 5 to save the data.

6-5-3 (b) Video Gain Adjustment

(60

kHz/75

Hz, Green box pattern)

Front Bezel

Opening

Back Raster

Green Window

Figure

6-7.

Green Box

Pattern

1. Display the green window pattern using a

range for which the ACL Circuit is not active (within ranges

l/3

1/2H

and

l/3 ;

.___._

Q2V).

*. I_.

6 Alignments and Adjustments

Turn the contrast and the brightness

controls fully clockwise. Press buttons 6 and 7 (G-Gain control) to

adjust the brightness of the green gain to

37-+1 ft-L.

Note: If you can’t increase the green gain to the appropriate value, press button 3 to increase the ACL point.

6-5-3 (c) White Balance Adjustment

(60

kHz/75

Hz, Full white Pattern)

Front

Sezel

Opening Back Raster White Window

Figure

6-8. Full White Pattern

1. Turn the contrast and the brightness

controls fully clockwise.

2. Use the R-Gain buttons 1 and 2 and B-Gain buttons

and

12 to

make the video white. (For 9300” K color adjustment: x = 0.283&.02,

y = 0.298&.02.)

Note: Do not touch buttons 6 and 7.

3. Press button 5 to save the data.

6-5-3 (d) White Balance Fine Adjustment

(x =

0.283&.02,

y = 0.298&.02,

Full White pattern)

Note: Do not touch buttons 6 and 7 (G-Gain).

Adjust the contrast control so that the brightness of the video is about 5 ft-L.

Check whether the white coordinates of the video meets the above coordinate

spec.

Adjust the contrast control so that the brightness of the video is about 20 ft-L.

Check whether the white coordinates of the video satisfies the above

spec.

If the white balance differs from the above

spec, readjust it to within specifications.

When correct, press buttons 5 to save.

6-5-3 (e) ACL point Adjustment

Display the full white pattern. Turn the contrast and the brightness

controls fully clockwise. Press buttons 3 and $ (ACL) so that the

brightness is 30 +l ft-L. Press button

to save the ACL setting

value.

6-5-4

Color Adjustments for

6500°K

6-5-4 (a) Back Raster Color Adjustment

Display the back raster pattern.

2. Turn the contrast and the brightness controls fully clockwise.

3. Press button 9 to load the standard color data (channel 2) for 6500’K from micom control jig.

4. Adjust the brightness of the back raster to

0.5 to 1.0 ft-L using buttons 21 or 22 (G-Bias control). If you don’t need to adjust the brightness, skip this step.

Note: For 6500” K adjustments you must not

control the screen VR of the FBT. If you do

so, the 9300°K setting values are changed.

5. Using buttons

16,17,26

and 27, adjust the

R-Bias to x =

0.313&.02

and B-Bias to

y=O.329-+0.02.

6. Press button 5 to save the bias data for 6500°K.

6-5-4 (b) Video Gain Adjustment

1. This procedure is the same as that of 9300°K.

2. Refer to the procedure for 9300°K on page 6-6.

6-5-4 (c) White Balance Adjustment

^. .

Display a full white pattern.

Turn the contrast and the brightness

controls fully clockwise. Using buttons

1,2,11

and 12 set the R/B

gain data td x=0.313&.02,

y=O.329&.02.

SC-726GXL

6-7

6 Alignmenmts and Adjustments

6-5-4 (d) White Balance Fine Adjustment

6-5-4 (e) ACL Point Adjustment

Refer to the procedure for 9300°K on page 6-7.

Refer to the procedure for 9300°K on page

6-7.

6-6 Focus Adjustment

Display the H character pattern so that the

Adjust the focus control of the FBT to display

focus adjustment can be done. (Apply

the sharpest image possible.

1280x1024/60

Hz mode to the monitor.)

Use locktite to seal the focus control in

Turn the contrast and the brightness controls

position.

fully clockwise.

6-7 Color Purity Adjustment

Color purity is the absence of undesired color. Conspicuous mislanding (unexpected color in a uniform field) within the display area shall not be

visible at a distance of 50 cm from CRT surface.

Conditions

Direction

Monitor facing east. Display image: White flat field. Luminance

Cutoff point at the center of

display area.

Note: Color purity adjustments should only be a

attempted by qualified personnel.

For trained and experienced service technicians only.

Use the following procedure to correct minor color

purity problems:

Make sure the display is not affected by external magnetic fields. Use an external degaussing coil to neutralize magnetic fields which may be affecting color purity.

Very carefully break the glue seal between the two-pole purity convergence magnets (PCM), band and the spacer (see Figure

6-10).

Caution: The convergence bow magnets are not user or service technician adjustable. Do not allow these magnets to move.

Make sure the spacing between the PCM assembly and the CRT stem is 29

mm&l

mm.

Display a red pattern over the entire display area.

Adjust the purity magnet rings on the PCM assembly to display a pure red pattern. (Optimum setting:

X=0.625&0.015,

Y=0.340?O.015)

Adjust each comer and the center to meet the

red color tolerances listed below.

Repeat steps 4 through 6 using a green pattern and again, using a blue pattern.

Table 6-6. Color Purity Tolerances

X=O.63a.O2 Y=O.34&.02

x=0.2&0.02 Y=O.61&.02

X=0.15+0.02

Y=O.O7+0.02

(For 9300°K color adjustment: X=0.283&.02,

Y=O.298~tO.O2)

When you have the PCMs properly adjusted, carefully glue them together to prevent their movement during shipping.

=_.I

I-._..

6-8

SC-726GXt.

6 Alignmenmts and Adjustments

6-8 Convergence Adjustments

Misconvergence occurs when one or more of the electron beams in a multi beam CRT fail to meet the other beams at a specified-point.

Table 6-7. Misconvergence Tolerances

Position

Error in mm CRT Dot Pitch

Remark

Center

(A)

0.30 0.26

Edge

(B)

0.30 0.26

800x600

resolution

0.40 0.26

800x600 resolution

306

Figure 6-9 Convergence Measurement Areas

6-8-l Static (Center) Convergence

Static convergence involves the alignment of the red, blue and green lines in the center area of the display. See Dynamic Convergence” for alignment of the

color fields around the edges of the display.

Conditions

Direction

Monitor facing east Warm-up: 30 minutes Display image: Crosshatch pattern Tolerances : See Table 6-7

As shown in Figures 6-10, CRTs used in these monitors all have the same magnet configuration as shown in Table 6-8 below.

Table 6-8. Magnet Configurations Magnet Order from Front of CRT

Convergence bow, two-pole, four-pole, six-pole

Use the following steps to correct any static misconvergence:

Locate the pair of four-pole magnet rings.

Unlock the rings and rotate the individual rings (change the spacing between tabs) to

converge the vertical red and blue lines.

Rotate the pair of rings (maintaining the spacing between tabs) to converge the

horizontal red and blue lines. After completing the red and blue center

convergence adjustment, locate the pair of

pole magnet rings. Rotate the individual rings (change the

spacing between tabs) to converge the vertical red and blue (magenta) and green lines.

Rotate the pair of rings (maintaining the spacing between tabs) to converge the horizontal red and blue (magenta) and green lines. Don’t rotate the 2-pole magnets, as they adjust for color purity.

Mark the correct position for the magnets and apply a small line of glue to hold the magnets in place. Lock the rings in place.

6-8-Z Dynamic (Edge) Convergence

Use the following procedure to correct minor dynamic (edge) misconvergence. If, after using this procedure, dynamic, misconvergence is still greater than the tolerance around the periphery of the display area, contact the Regional Service Center for possible CRT replacement.

Make sure the display is not affected by

external magnetic fields.

Make sure the static convergence is properly adjusted.

Strategically place small magnetic strips on the back of the CRT to correct the misconvergence. Be careful not to remove the paper protecting the adhesive on the magnetic strip until you are satisfied with their placement and the dynamic convergence.

When you are satisfied with the convergence around the edge of the CRT, permanently glue the magnets to the back of the CRT.

Table 6-9. Magnetic Strips

Warning Do not remove or change the position of

the factory installed wedges. These wedges were installed by the CRT

manufac&er

and are properly placed for this CRT. Removal may result in damage to the CRT.

SC-726GXL

6-9

_. .

“s.

*. ._

6 Alignments and Adiustments

---

i!__IS

Figure 6-10. Magnet Configuration

Red and Blue Alignment

Red, Blue and Green Alignment

(Qpole

magnet movement)

(6-pole magnet movement)

Shii direction of

Crosshatch

Pattern

Crosshatch

Pattern

Figure 6-l

Magnet Movements

‘.

6-10

SC-726GXL

6 Alignments and Adjustments

6-8-3 Bow Convergence Adjustments

Conditions

Direction: Monitor facing

East_

Display Image: Crosshatch pattern mixed with RGB colors.

Bow convergence adjustments are not available for any of the CRTs used in the SC-726GXL. While all

the CRTs have bow convergence magnets, they are sealed in the CRT factory and are not user or service technician adjustable. Do not touch these magnets (see Figures 6-10). If color convergence bow adjustment is out of alignment, replace the CRT. Bow misconvergence should not exceed the values listed in Table 6-7: Misconvergence tolerances.

6-8-4 Balance Convergence Adjustments

Balance Convergence involves the alignment of the red and blue lines when they are misaligned at one end more so than at the other (X). The deflection yoke holds the balance coils which

can

correct balance misconvergences.

Horizontal

Balance Coil

Figure 6-12.

Samsung

and Hitachi Deflection Yoke

YilC

Figure 6-13. New Hitachi Deflection Yoke

6-8-4 (a) Horizontal Line Red and Blue Balance

Convergence

Figure 6-14. Horizontal Line Balance Misconvergence

Use a

#/O

hexdriver at the Horizontal Balance Coil (Xv). Turning the VR to the right raises the right end of the blue line and lowers the left end. Turning the VR to the left lowers the right end of the blue line and raises the left end.

6-8-4 (b) Vertical Red and Blue Balance

Convergence

BlUl?

Red

Figure 6-15. Vertical Line Balance Misconvergence

Use a #O screwdriver (flat-head [-_I for

Samsung and Hitachi DYs and Phillips type [+]

for Matsushita [Panasonic]

DYs)

at the YH variable register. Turning the VR to the left tilts the blue line to the right. Turning it to the right tilts the blue line to the left.

6-8-4 (c) Upper and Lower Horizontal Line

Convergence

Red

Blue

________________._.-.-.--

Red

Blue

___.__________._._...--~

Figure 6-16. Upper and Lower Balance Misconvergence

Use a #O screwdriver (flat-head

[-_I

for Samsung

and Hitachi

DYs

and phillips type [+] for

Matsushita [Panasonic]

DYs)

at the Yv variable register. Turning the VR to the left moves the blue line at the top upward and at the bottom the line moves downward. Turning it to the right moves the blue line at the tq downward and at the bottom the line moves upward.

SC-726GXL

6-l

_. . _

7 Troubleshooting

Notes:1,If picture does not appear, fully rotate the brightness and contrast controls clockwise before inspection.

Check the following circuits:

*No

raster appears: Power circuit, horizontal output circuit, H/V control circuit and H/V output circuit. *High voltage develops but no raster appears: Video output circuits. *High voltage does not develop: Horizontal output circuits.

Horizontal line on raster

Check the power supply circuits.

(D618 and

R316)

Yes

Check the power supply circuits.

I::::_..:fi?-A~7rat::_“‘~~

_. . _

* --_.

*. ._ :

SC726GXL

7-l

7 Troubleshooting

Verticai

line on raster

Does drive pulse appear

Check the horizontal drive

circuits.

(IC401)

Yes

Does drive pulse appear

at emitter of

Q402?

Check the push-pull circuits.

(Q402

and

Q403)

Yes

Does drive output pulse

appear at drain

Q401?

Replace

Cl401

or check its

related circuits. (D407, 0408,

D409 and T401)

Yes

(

Check

flyback

pulse at collector

Check rhe H-size Drive &

of Q407 connection of

CN401

and its related circuits

0410)

output circuits

(D404,

Q405, Q406

and

R431)

+ 85 hidden pages

Samtron SC-726GXL Service Manual

Specifications and Main Features

Frequently Asked Questions

User Manual