Viewsonic VX750-1 Service Manual

Service Manual

ViewSonic VX7501

Model No. VLCDS27089-1W

17” Color TFT LCD Display

ViewSonic

(VX750_SM_755 Rev. 1a Apr. 2004)



381 Brea Canyon Road, Walnut, California 91789 USA - [phone]

Copyright

Copyright
reproduced, transmitted, transcribed, stored in a retrieval system, or translated into any language or
computer language, in any form or by any means, electronic, mechanical, magnetic, optical, chemical,
manual or otherwise, without the prior written permission of ViewSonic Corporation.

Disclaimer

ViewSonic makes no representations or warranties, either expressed or implied, with respect to the
contents hereof and specifically disclaims any warranty of merchantability or fitness for any particular
purpose. Further, ViewSonic reserves the right to revise this publication and to make changes from time
to time in the contents hereof without obligation of ViewSonic to notify any person of such revision or
changes.

Trademarks

Optiquest is a registered trademark of ViewSonic Corporation.
ViewSonic is a registered trademark of ViewSonic Corporation.
All other trademarks used within this document are the property of their respective owners.

2004 by ViewSonic Corporation. All rights reserved. No part of this publication may be

¤

Revision History

Revision Date Description Of Changes Approval

1a 04/27/04 Initial Release DCN-3772 Angela Lu

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TABLE OF CONTENTS

1. Precautions and Safety Notices

2. Specification

3. Front Panel Function Control Description

4. Circuit Description

5. Adjusting Procedure

6. Trouble Shooting Flow Chart

7. Recommended Spare Parts List

8. Exploded Diagram And Spare Parts List

9. Block Diagram

10. Schematic Diagrams

11. PCB Layout Diagrams

1

2
3

9
21
38

46
51
53
56

64

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1. Precautions and Safety Notices

1. Caution :

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

2. Safety Check :

Care should be taken while servicing this LCD display, due to the high voltage used in the inverter circuit.
High voltage is exposed in such areas as the associated transformer circuits .

3. POWER SUPPLY REQUIREMENTS

The external power converter for this display utilizes AC and DC cords. The AC cord is detachable , but the
DC cord is permanently attached . Any attempt to replace another adapter could result in damage to the display .

4. LEAKAGE CURRENT HOT CHECK

4-1 Plug the AC cord directly into the AC outlet. Do not use an isolation transformer during this check.
4-2 Connect a 1500 ohm , 10 watt resistor , paralleled with a 0.15uF capacitor between each metallic part

and a good earth ground

4-3 Use an AC voltmeter with 1000 ohm / volt or more sensitivity and measure the AC voltage across the

combination 1500 ohm resistor and 0.15uF capacitor.
4-4 Move the resistor connection to each exposed metallic part and measure the voltage.
4-5 Reverse the polarity of the AC plug in the AC outlet and repeat the above measurement.
4-6 Voltage measured must not exceed 1.5 volt RMS, from any exposed metallic part to the ground. A leakage

current tester may be used in the above hot check, in which case any circuit measured must not exceed 1.0

milliamp. In the case of a measurement exceeding the 1.0 milliamp value, a rework is required to eliminate the

chance of a shock hazard .

AC VOLTMETER

V

0.15u
.

To Metal Parts

1500 10W

Earth Ground

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2. Specification

Mechanical :
Dimension ( W
Set a. with stand:
b. Without stan 502 x 340 x 63 mm

Base (L X W): 275 x 195 mm
Packing : ( W x H x D ) mm: 572 x 491 x 240
Weight : Net / Gross ( Kg ): 5.6 / 8.2
Wall Mount (VESA): 100 x 100
LCD Panel type: QDI / QD17EL07
Max. resolution (HxV) : 1280 x 1024
Nominal picture size (HxV): 338 mm x 270
Display colors: 16.2 M ( 6 bit + dith
Dot pitch: 0.264 mm
Response time: 4 +1 2 / 16ms (Tr +
Brightness (100% whi ) Typical : 270 cd/m² , Min. 220cd
Contrast : Typical : 450:1, Min. 300:1
Viewing angle : 75 / 75 /65 / 60 (L/R/T/B CR>=10)
Synchronization: Fh = 31~82 KHz / Fv=50~85Hz

x H x D ) mm

502 x 405 x 195 mm

d:

mm

mm

mm

ering )

Tf / typical)

te : /m²

Presets: 18 timing modes
OSD Language : 9 languages
Color Temperature : sRGB , 6500°K (default)
5400°K / User R,G,B
Plug & Play : DDC1/2B interface
Scaler chip: Mstar MST 8131
Audio Input Connector: 3.5 mm Stereo, PC2001
Audio Amplifier : 5W x 2 (chip :TPA3002)
AC Power range: 90 V ~ 264 V, 50 Hz / 60
Power consumption: < 50W green / < 1W amber
(On / Off mode)

/ 9300°K

Hz

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3. Front Panel Function Control Description

Adjusting the Screen Image

Use the buttons on the front control panel to display and adjust the OnView

®

controls which display on the screen. The OnView controls are explained at the
top of the next page.

1 MENU : Displays the Main Menu or exits the control screen and saves adjustments.

VOL- / VOL+ : Decreases or increases volume.

UP / DOWN : Scrolls through menu options and adjusts the displayed control.

Also a shortcut to display the Contrast adjustment control screen.

2 Enter : Displays the control screen for the highlighted control.
Also a shortcut to Auto Image Adjust.

INPUT SELECT : Also toggles between two controls on some screens.

Power On / Off

Power light

Blue = ON
Orange = Power Saving

Main Menu
With OnView controls

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Do the following to adjust the screen image:

1

To display the Main Menu, press button [1].

NOTE: All OnView menus and adjustment screens disappear automatically

after about 15 seconds. This time period is adjustable through the Setup
menu and the OSD timeout control described on page 11.

2

To highlight a control you want to adjust, press I or J to scroll up or down
the Main Menu.

3

To select the highlighted control, press button [2]. A control screen appears
like the example shown below.

Contrast

1:EXIT 2: Brightness

4

To adjust the control, press the upIor downJbuttons.

5

To save the adjustments and exit the menu, press button [1] twice.

The line at the
bottom of the
screen tells you
what you can do
next: Exit or Select
the control that is
highlighted.

The following tips may help you optimize your display:

• Adjust your computer's graphic card so that it outputs a video signal 1280 x
1024 @ 60 Hz to the LCD dislay. (Look for instructions on “changing the
refresh rate” in your graphic card's user guide.)

• If necessary, make small adjustments using H. POSITION and V. POSITION
until the screen image is completely visible

. (The black border around the
edge of the screen should barely touch the illuminated “active area” of the
LCD dislay.)

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Main Menu Controls

Adjust the menu items shown belowbyusing the up Iand downJbuttons.

Control Explanation

Auto Image Adjust

automatically sizes, centers, and fine tunes the

video signal to eliminate waviness and distortion.
Press the [2] button to obtain a sharper image.

NOTE

: Auto Adjust works with most common video cards. If

this function does not work on your LCD dislay, then lower the
video refresh rate to 60 Hz and set the resolution to its pre-set
value.

Contrast

adjusts the difference between the image background

(black level) and the foreground (white level).

Brightness

Color Adjust

adjusts background black level of the screen image.

provides several color options: preset color
temperatures and User which allows you to adjust red (R), green
(G), and blue (B). The factory setting for this product is 6500K
(6500 Kelvin).

sRGB

— sRGB is quickly becoming the industry standard for color
management, with support being included in many of the latest
applications. Enabling this setting allows the LCD display to
more accurately display colors the way they were originally
intended. Enabling the sRGB setting will cause the Contrast and
Brightness adjustments to be disabled.

9300K

— Adds blue to the screen image for cooler white (used

in most office settings with fluorescent lighting).

6500K

— Adds red to the screen image for warmer white and

richer red. Default setting.

5400K — Adds green to the screen image for a darker color.

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Control Explanation

User

— Individual adjustments for red, green, and blue.

1

To select color (R, G or B) press button [2].

2

To adjust selected color, press I or J.

3

When you are finished making all color adjustments, press
button [1] twice.

Important

: If you select RECALL from the Main Menu when
the product is set to a Preset Timing Mode, colors return to the
6500K factory preset.

Input Select

allows you to toggle between an analog and a

digital signal.

i

Information

coming from the graphics card in your computer. See your

displays the timing mode (video signal input)

graphic card’s user guide for instructions on changing the
resolution and refresh rate (vertical frequency).

VESA 1280 x 1024 @ 60 Hz (recommended) means that the
resolution is 1280 x 1024 and the refresh rate is 60 Hertz.

Manual Image Adjust

The Image Adjust controls are explained below:

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Control Explanation

H./V. Position

adjusts horizontal and vertical position of the
screen image. You can toggle between Horizontal and Vertical
by pressing button [2]. Horizontal moves the screen image to
the left or to the right. Vertical moves the screen image up and
down.

H. Size

NOTE:

Fine Tune sharpens focus by aligning the illuminated text and/

(Horizontal Size) adjusts the width of the screen image.

Vertical size is automatic with your LCD dislay.

or graphic characters.

NOTE: Try the Auto Adjust (see page 9) before using the Fine

Tune control.

Sharpness

adjusts the clarity and focus of the screen image.

?

Setup Menu displays the menu shown below.

The Setup Menu controls are explained below.

L

anguage

Select allows you to choose the language used in

the menus and control screens.

Resolution Notice

advises the optimal resolution to use.

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Control Explanation

OSD

OSD

OSD Position

allows you to move the on-screen display menus

and control screens.

OSD Timeout

sets the length of time an on-screen display
screen is displayed. For example, with a “15 second” setting, if
a control is not pushed within 15 seconds, the display screen
disappears.

OSD Background

allows you to turn the On-Screen display
background on or off. This means that while making adjustments
from the OSD control screens you can also view open software
applications, or the Windows desktop.

Memory Recall

returns adjustments to the original factory
settings if the display is operating in a factory Preset Timing
Mode listed in this user guide.

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4. Circuit Description

1. Outline

1.1 Po

wer On/Off, up arrow button, down arrow button, VOL- button, VOL+ button, 1MENU button, 2Enter
button and INPUT SELECT button on the top bezel.
D-sub 15pin connector, DVI-D connector, audio line-i

1.2 n receptacle, audio line-out receptacle, earphone jack

and DC-IN jack are loc ated on the back side of the cabinet.

1.3

OSD menu includes the following function;

Auto Image Adjust (only active under ana

log input)
Contrast/Brightness
Audio Adjust
Color Adjust
Information
Manual Image Ad

Setup Menu

Memory Reca

1. Contrast and Bright

4 ness can be directly controlled with UP / DOWN key.

1.5 Audio volume can be controlled with VOL- key and VOL+ key. When Audi

2Enter key can disable audio output.

2. Conne

ctors

2.1 AC inlet : CEE2

2.2 Audio : Line-in, Line-out and Earphone re

CN9

1
5
4
3
2

just

ll

2 type connector

CN13

ceptacles

1
5
4
3
2

1

2

6

5

3

4

CN12

o Adjust menu is active, pushing

Line-in receptacle Line-out receptac Earphone recepta

(Line-in receptacle is green, line-out receptacle is blue, earphone jack is black.)

2.3 Video signal connector for analog input: 15P Mini D-Sub

le cle

PIN MNEMONI SIGNAL

1 RV Red Video

2 GV Green Video

3 BV Blue Video

4 NC None

5 GND Ground (DDC

return)

6 RG Red GND

7 GG Green GND

8 BG Blue GND

9 +5V +5V (for DDC)

10 SG Sync GND

11 NC None

12 SDA DDC Data

13 HS Horizontal Sync

14 VS Vertical Sync

15 SCL DDC Clock

16

1

11

6

2

7

3

8

4

9

12

13

14

5

15

10

CN6

DB15HD

17

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2.4 Video signal connector for digital input: 24pin DVI-D connector

CN9

RX2-

RX2+

GND

RX4-

RX4+

RX1-

RX1+

GND

RX3-

RX3+

GND

RX0-

RX0+

GND

RX5-

RX5+

GND

RXC+

RXC-

DVI-D

SCL

SDA

VS

HP

5V

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

Pin

Signal Name Description

No.

1 RX2- TMDS negative differential input,

channel 2

2 RX2+ TMDS positive differential input,

channel 2
3 GND Logic Ground
4 RX4- Reserved. No connection
5 RX4+ Reserved. No connection
6 SCL DDC2B Clock
7 SDA DDC2B Data
8 VS Reserved. No connection
9 RX1- TMDS negative differential input,

channel 1

10 RX1+ TMDS positive differential input,

channel 1

11 GND Logic Ground
12 RX3- Reserved. No connection
13 RX3+ Reserved. No connection
14 +5V Power
15 GND Logic Ground
16 HP SENSE Pin, Pull High
17 RX0- TMDS negative differential input,

channel 0

18 RX0+ TMDS positive differential input,

channel 0

19 GND Logic Ground
20 RX5- Reserved. No connection
21 RX5+ Reserved. No connection
22 GND Logic Ground
23 RXC+ TMDS positive differential input,

reference clock

24 RXC- TMDS negative differential input,

reference clock

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3. ELECTRICAL SPECIFICATIONS

3.1 Standard conditions

3.2 POWER

3.2.1 Power supply

Display Area

Video Signal

Contrast

Brightness

Ambient

Input

Warming up

Display

337.9 x 270.3 mm

0.7Vpp

Max.

Max.

20 +/- 5 °C

AC

> 30 min

1280 x 1024

Input voltage 100~240Vac
Power frequency 50~60Hz
Input current

<1.5Arms@90Vac

Inrush current

<0.8Arms@180Vac

50A(Max) at 120Vac(cold start)
Power consumption 38W(typical);50Watts(Max)
Output voltage @0-4.16A Load 12 Vdc+/-5%

3.2.2 Power Management

State Power Indicator

On 45Watts Blue
Standby < 1Watts Amber
Off <1Watts Off

3.3 Acceptable timing

If the timing is within following specification, this LCD display can automatically function with a certain position.

Horizontal: Sync frequency: 30~82 kHz
Vertical: Sync frequency: 56~85Hz

3.4 Signal level and input impedance

3.4.1 Video Signal level: 0.7Vp-p Video signal.

3.4.2 Sync Signal level

H/V Separate: TTL level

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3.4.3 Input impedance

Analog video input: 75 ohm
Digital video input: 100 ohm
Sync input: > 1 k ohm
Audio input: 10K ohm

4. Signal Cable: Signal cable with Mini D-Sub 15P connectors at both ends. Length: 1.8 meter.

5. EDID DATA

18.1 Analog EDID

TIME: 15:48:11

DATE: WED AUG 13, 2003

______________________________________________________________________
______________________________________________________________________

VIEWSONIC CORPORATION

EDID VERSION # 1, REVISION # 3

DDCTEST FOR: VIEWSONIC VX750

______________________________________________________________________
______________________________________________________________________

128 BYTES OF EDID CODE:

0 1 2 3 4 5 6 7 8 9
________________________________________

0 | 00 FF FF FF FF FF FF 00 5A 63
10 | 14 D7 01 01 01 01 01 0D 01 03
20 | 0E 22 1B 78 2E 0C 55 A2 56 4C
30 | 96 25 1A 50 54 BF EF 80 81 80
40 | 81 40 71 4F 01 01 01 01 01 01
50 | 01 01 01 01 30 2A 00 98 51 00
60 | 2A 40 30 70 13 00 52 0E 11 00
70 | 00 1E 00 00 00 FF 00 41 32 4E
80 | 30 33 30 31 30 30 30 30 31 0A
90 | 00 00 00 FD 00 32 4B 1E 50 0E

100 | 00 0A 20 20 20 20 20 20 00 00
110 | 00 FC 00 56 58 37 35 30 0A 20
120 | 20 20 20 20 20 20 00 21

______________________________________________________________________
(08-09) ID MANUFACTURER NAME = VSC
(11-10) PRODUCT ID CODE = D714
(12-15) LAST 5 DIGITS OF SERIAL NUMBER = NOT USED
(16) WEEK OF MANUFACTURE = 01

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(17) YEAR OF MANUFACTURE = 2003
(10-17) COMPLETE SERIAL NUMBER = SEE DESCRIPTOR BLOCK
(18) EDID VERSION NUMBER = 1
(19) EDID REVISION NUMBER = 3
(20) VIDEO INPUT DEFINITION:
ANALOG SIGNAL

0.700, 0.300 (1.000 VP-P)

SEPARATE SYNCS, COMPOSITE SYNC, SYNC ON GREEN
(21) MAXIMUM HORIZONTAL IMAGE SIZE = 340 MM
(22) MAXIMUM VERTICAL IMAGE SIZE = 270 MM
(23) DISPLAY GAMMA = 2.20
(24) POWER MANAGEMENT AND SUPPORTED FEATURE(S):

ACTIVE OFF/VERY LOW POWER, STANDARD DEFAULT COLOR SPACE,

PREFERRED TIMING MODE

DISPLAY TYPE = R/G/B COLOR
(25-34) CHROMA INFO:

RED X - 0.633 GREEN X - 0.300 BLUE X - 0.146 WHITE X - 0.313
RED Y - 0.336 GREEN Y - 0.586 BLUE Y - 0.103 WHITE Y - 0.329

(35) ESTABLISHED TIMING I:

720 X 400 @ 70HZ (IBM,VGA)
640 X 480 @ 60HZ (IBM,VGA)
640 X 480 @ 67HZ (APPLE,MAC II)
640 X 480 @ 72HZ (VESA)
640 X 480 @ 75HZ (VESA)
800 X 600 @ 56HZ (VESA)
800 X 600 @ 60HZ (VESA)

(36) ESTABLISHED TIMING II:

800 X 600 @ 72HZ (VESA)

800 X 600 @ 75HZ (VESA)

832 X 624 @ 75HZ (APPLE,MAC II)

1024 X 768 @ 60HZ (VESA)

1024 X 768 @ 70HZ (VESA)

1024 X 768 @ 75HZ (VESA)

1280 X 1024 @ 75HZ (VESA)
(37) MANUFACTURER'S RESERVED TIMING:

1152 X 870 @ 75HZ (APPLE,MAC II)

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(38-53) STANDARD TIMING IDENTIFICATION:

1280 X 1024 @60HZ
1280 X 960 @60HZ
1152 X 864 @75HZ
NOT USED

NOT USED
NOT USED
NOT USED

NOT USED
______________________________________________________________________
(54-71) DETAILED TIMING / DESCRIPTOR BLOCK 1:

1280X1024 PIXEL CLOCK: 108.00 MHZ

______________________________________________________________________

HORIZONTAL IMAGE SIZE: 338 MM VERTICAL IMAGE SIZE: 270 MM

REFRESHED MODE: NON-INTERLACED NORMAL DISPLAY - NO STEREO

HORIZONTAL:
ACTIVE TIME: 1280 PIXELS BLANKING TIME: 408 PIXELS
SYNC OFFSET: 48 PIXELS SYNC PULSE WIDTH: 112 PIXELS
BORDER: 0 PIXELS FREQUENCY: 63.98 KHZ

VERTICAL:
ACTIVE TIME: 1024 LINES BLANKING TIME: 42 LINES
SYNC OFFSET: 1 LINES SYNC PULSE WIDTH: 3 LINES
BORDER: 0 LINES FREQUENCY: 60.02 HZ

DIGITAL SEPARATE, HORIZONTAL POLARITY (+) VERTICAL POLARITY (+)

______________________________________________________________________
(72-89) DETAILED TIMING / DESCRIPTOR BLOCK 2:

MONITOR SERIAL NUMBER:
A2N030100001

______________________________________________________________________
(90-107)DETAILED TIMING / DESCRIPTOR BLOCK 3:

MONITOR RANGE LIMITS:
MIN VERTICAL FREQ - 50 HZ
MAX VERTICAL FREQ - 75 HZ
MIN HORIZ. FREQ - 30 KHZ
MAX HORIZ. FREQ - 80 KHZ
PIXEL CLOCK - 140 MHZ
SECONDARY GTF - NOT SUPPORTED

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(108-125) DETAILED TIMING / DESCRIPTOR BLOCK 4:

MONITOR NAME:

(126) NO EXTENSION EDID BLOCK(S)

VX750

(127) CHECKSUM OK

18.2 Digital EDID

Time: 15:50:10

Date: Wed Aug 13, 2003

______________________________________________________________________
______________________________________________________________________

VIEWSONIC CORPORATION

EDID Version # 1, Revision # 3

DDCTest For: ViewSonic VX750

______________________________________________________________________
______________________________________________________________________

128 BYTES OF EDID CODE:

0 1 2 3 4 5 6 7 8 9

________________________________________

0 | 00 FF FF FF FF FF FF 00 5A 63
10 | 14 D7 01 01 01 01 01 0D 01 03
20 | 80 22 1B 78 2E 0C 55 A2 56 4C
30 | 96 25 1A 50 54 BF EF 80 81 80
40 | 81 40 71 4F 31 0A 01 01 01 01
50 | 01 01 01 01 30 2A 00 98 51 00
60 | 2A 40 30 70 13 00 52 0E 11 00
70 | 00 1E 00 00 00 FF 00 41 32 4E
80 | 30 33 30 31 30 30 30 30 31 0A
90 | 00 00 00 FD 00 32 4B 1E 50 0E

100 | 00 0A 20 20 20 20 20 20 00 00
110 | 00 FC 00 56 58 37 35 30 0A 20
120 | 20 20 20 20 20 20 00 76

______________________________________________________________________

(08-09) ID Manufacturer Name = VSC
(11-10) Product ID Code = D714
(12-15) Last 5 Digits of Serial Number = Not Used
(16) Week of Manufacture = 01

(17) Year of Manufacture = 2003
(10-17) Complete Serial Number = See Descriptor Block

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(18) EDID Version Number = 1
(19) EDID Revision Number = 3
(20) VIDEO INPUT DEFINITION:

Digital Signal
Non - VESA DFP 1.x Compatible

(21) Maximum Horizontal Image Size = 340 mm
(22) Maximum Vertical Image Size = 270 mm
(23) Display Gamma = 2.20
(24) Power Management and Supported Feature(s):

Active Off/Very Low Power, Standard Default Color Space,
Preferred Timing Mode
Display Type = R/G/B Color

(25-34) CHROMA INFO:

Red X - 0.633 Green X - 0.300 Blue X - 0.146 White X - 0.313
Red Y - 0.336 Green Y - 0.586 Blue Y - 0.103 White Y - 0.329

(35) ESTABLISHED TIMING I:

720 X 400 @ 70Hz (IBM,VGA)
640 X 480 @ 60Hz (IBM,VGA)
640 X 480 @ 67Hz (Apple,Mac II)
640 X 480 @ 72Hz (VESA)
640 X 480 @ 75Hz (VESA)
800 X 600 @ 56Hz (VESA)
800 X 600 @ 60Hz (VESA)

(36) ESTABLISHED TIMING II:

800 X 600 @ 72Hz (VESA)
800 X 600 @ 75Hz (VESA)

832 X 624 @ 75Hz (Apple,Mac II)
1024 X 768 @ 60Hz (VESA)
1024 X 768 @ 70Hz (VESA)
1024 X 768 @ 75Hz (VESA)
1280 X 1024 @ 75Hz (VESA)

(37) Manufacturer's Reserved Timing:

1152 X 870 @ 75Hz (Apple,Mac II)

(38-53) Standard Timing Identification:

1280 X 1024 @60Hz
1280 X 960 @60Hz

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1152 X 864 @75Hz
640 X 400 @70Hz
Not Used
Not Used
Not Used
Not Used

(54-71) Detailed Timing / Descriptor Block 1:

1280x1024 Pixel Clock: 108.00 MHz

Horizontal Image Size: 338 mm Vertical Image Size: 270 mm

Refreshed Mode: Non-Interlaced Normal Display - No Stereo

Horizontal:
Active Time: 1280 pixels Blanking Time: 408 pixels
Sync Offset: 48 pixels Sync Pulse Width: 112 pixels
Border: 0 pixels Frequency: 63.98 KHz

Vertical:
Active Time: 1024 lines Blanking Time: 42 lines
Sync Offset: 1 lines Sync Pulse Width: 3 lines
Border: 0 lines Frequency: 60.02 Hz

Digital Separate, Horizontal Polarity (+) Vertical Polarity (+)

(72-89) Detailed Timing / Descriptor Block 2:

Monitor Serial Number:
A2N030100001

(90-107) Detailed Timing / Descriptor Block 3:

Monitor Range Limits:
Min Vertical Freq - 50 Hz
Max Vertical Freq - 75 Hz
Min Horiz. Freq - 30 KHz
Max Horiz. Freq - 80 KHz

Pixel Clock - 140 MHz
Secondary GTF - Not Supported

(108-125) Detailed Timing / Descriptor Block 4:

Monitor Name:

VX750
(126) No Extension EDID Block(s)
(127) CheckSum OK

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6. THEORY OF OPERATION

This section describes the function of the LCD monitor per functional block.
This monitor includes MB board, inverter board, adapter and two button boards.

6.1 MB BOARD

The MB board is a two-layer, single-landed. 12V DC power from the power adapter enters the board through
DC jack. Other connectors on the board are for inverter, audio and button boards .The VGA cable is a signal
cable that contains video signal, sync signal and DDC signal from PC VGA adapter. This system board consists
of 4 functional areas: flat panel controller, flash ROM, power regulator and Audio amplifier

6.1.1 Flat panel controller… MST1831A (U3)
The heart of the system board is the scalar chip of MST1831A. The MST1831A is a high performance, dual
input graphics processing IC for LCD monitors with resolutions up to SXGA. It provides all key IC functions
required for LCD panel. On-chip functions include an 8-bit triple ADC, PLL, DVI receiver, high scaling engine,
OSD controller and dual LVDS transmitter.

a) Clock Generation:

Crystal Input Clock (XIN and XOUT): This is the input pair to an internal crystal oscillator and corresponding

logic. A 14.318 MHz crystal is recommended.

b) Hardware Reset (Pin 32):

Hardware Reset signal is provided by MCU (U6). It is active high.

c) Analog to Digital Converter:

The MST1831A chip has three ADC's (analog-to-digital converters), one for each color (red, green and
blue) .The analog RGB and synchronous signals are connected to MST1831A as described below:

Pin Name Pin Number
Red + 63
Red - 62
Green + 60
Green - 59
Blue + 58
Blue - 57
H sync 37
V sync 38

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d) OSD: The MST1831A has a fully programmable, high-quality OSD controller. The on-chip static RAM

stores the cell map and the cell definitions.

e) On chip TMDS receiver: The MST1831A integrated DVI receiver, which operates up to 135MHz and can

directly connect to all DVI compliant transmitters. The TMDS signals are connected to MST1831A
as described below:

Pin Name Pin NO.
R+ 40
R- 41
G+ 43
G- 44
B+ 46
B- 47
CK+ 49
CK- 50

f) PWM controlling function (Pin 73~74): The MST1831A has two dedicated PWM outputs of PWM0 and

PWM1 to control audio volume and back light brightness.

g) Serial interface ports (pin 70 and pin 71): This serial interface ports communicate with MCU and support

up to 400Kbit per second transmit rate.

h) Panel interface (Pin 1, Pin 102, Pin 103, Pin 106, Pin 107, Pin 120~ Pin 125, Pin 108~113, and Pin 128) :

The MST1831A driver interface is highly programmable. It supports dual bus / dual port for SXGA drivers.

6.1.2 Power Regulator AIC1563 (U9), LT1117 (U10, U11): The AIC1563 is a monolithic control IC containing

the primary functions required for DC-to-DC converters. The device consists of an internal temperature
compensated reference, comparator, controlled duty cycle.

Oscillator with an active current sense circuit, desired output voltage is determined by the equation,
Volt = 1.25 *(1 + R121 / R122), in this case, the output voltage are 5 Volts
The AIC1117 is a low dropout positive adjustable regulator with minimum of 800mA output current
capability. So it is well suited for 3.3 V and 2.5 V Regulator.
U10 as a 2.5V regulator, Desired output voltage is determined by the equation
Volt=1.25 x (1 + R124/R123)= 2.5
U11 as a 3.3V regulator, Desired output voltage is determined by the equation
Volt=1.255 x (1+ R126/R125)= 3.3

ViewSonic Corporation Confidential

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