ViewSonic VG720 - 17" LCD Monitor User manual

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ViewSonicCorporation Confidential - Do Not Copy VG720
ManufactureDate:Aug-10-05
Service Manual
ViewSonic VG720
Model No VS10791
17” Color TFT LCD Display

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ViewSonicCorporation Confidential - Do Not Copy VG720
Copyright
Copyright ©2005 by ViewSonic Corporation. All rights reserved. No part of this publication
may be reproduced, transmitted, transcribed, stored in a retrieval system, or translated into
any language or manual or otherwise, without the prior written permission of ViewSonic
Corporation.
Disclaimer
ViewSonic makes no representation or warranties, either expressed or implied, with
respect to the contents hereof and specifically disclaims any warranty of merchantability of
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.
Revision History
Revision Date Description of changes Approval
A00 Aug-10-05 Initial Release YG.WANG
A01 Dec-28-05
Update the Handing and Placing Methods
and the Circuit Description and the
Adjustment Procedure
YG.WANG

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TABLE OF CONTENTS
1. Precautions And Safety Notices 4
2. Specification 7
3. Front Panel Control And Indicators 10
4. CircuitDescription 16
5. AdjustmentProcedure 23
6. Troubleshooting Flow Chart 43
7. Recommended Spare Parts List 44
8. Exploded Diagram And Spare Parts List 61
9. DisassembleProcess 64
10. BlockDiagram 71
11. SchematicDiagram 72
12. PCBLayoutDiagram 79

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1. Precautions And Safety Notices
1.1 SAFETY PRECAUTIONS
This monitor is manufactured and tested on a ground principle that a user’s safety comes
first. However, improper use or installation may cause damage to the monitor as well as
the user. Carefully go over the following WARNINGS before installing and keep this guide
handy.
WARNINGS
．This monitor should be operated only at the correct power sources indicated on the label
on the rear end of the monitor. If you’re unsure of the power supply in your residence,
consult you local dealer or power company.
．Use only the special power adapter that comes with this monitor for power input.
．Do not try to repair the monitor your self as it contains no user-serviceable parts. This
monitor should only be repaired by a qualified technician.
．Do not remove the monitor cabinet. There is high-voltage parts inside that may cause
electric shock to human bodies, even when the power cord is unplugged.
．Stop using the monitor if the cabinet is damaged. Have it checked by a service technician.
．Put your monitor only in a clean, dry environment. If it gets wet, unplug the power cable
immediately and consult your service technician.
．Always unplug the monitor before cleaning it .Clean the cabinet with a clean, dry cloth.
Apply non-ammonia based cleaner onto the cloth, not directly onto the glass screen.
．Keep the monitor away from magnetic objects, motors, TV sets, and transformer.
．Do not place heavy objects on the monitor or power cord.
1.2 PRODUCT SAFETY NOTICE
Many electrical and mechanical parts in this chassis have special safety visual inspections
and the protection afforded by them cannot necessarily be obtained by using replacement
components rated for higher voltages, wattage, etc. Before replacing any of these
components read the parts list in this manual carefully. The use of substitute replacement
parts which do not have the same safety characteristics as specified in the parts list may
create shock, fire ,or other hazards.
1.3 SERVICE NOTES
1. When replacing parts or circuit boards, clamp the lead wires around terminals before
soldering.
2. When replacing a high wattage resistor(more than 1W of metal oxide film resistor) in
circuit board, keep the resistor about 5mm away from circuit board.
3. Keep wires away from high voltage, high temperature components and sharp edges.
4. Keep wires in their original position so as to reduce interference.
5. Usage of this product please refer to also user’s manual.

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1.4 HANDING AND PLACING METHODS
Correct Methods: Incorrect Methods:
Only touch the metal frame of the LCD
panel or the front cover of the monitor. Do
not touch the surface of the polarizer.
Surface of the LCD panel is pressed by fingers
and that may cause “Mura.”
Take out the monitor with cushions Taking out the monitor by grasping the LCD
panel. That may cause “Mura.”

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Place the monitor on a clean and soft foam
pad.
Placing the monitor on foreign objects. That
could scratch the surface of the panel or cause
“Mura.”
Place the monitor on the lap, the panel
surface must be upwards.
The panel is placed facedown on the lap. That
may cause “Mura.”

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2. Specification
2.1 PRODUCT SPECIFICATIONS
LCD Panel 17.0” TFT
Recommend Resolution 1280 x1024@60Hz
Pixel Dimension 0.264(H) x 0.264(V)mm
LCD Display Color 16.2M Colors (RGB 6-bit+FRC data)
Viewing Angle Horizontal: 140 °
Vertical: 125 °
Contrast Ratio 600：1 (Typ.)
Brightness 270 cd/㎡(Typ.)
Response Time 8ms(Typ.)
Active Display Area 337.920(H) x 270.336(V)
Maximum Pixel Clock 135 MHz
Horizontal Frequency 30 – 82 kHz
Vertical Refresh Rate 50 – 75 Hz.
Temperature Operating: 0°C to +40°C
Storage: -20°C to +60°C
Power Management
Energy Star compliant VESA
DPMS compatible
<1 W
Power Input Voltage : 90V~264V
Consumption: 48 Watts(Max.) 43 Watts(Typ.)

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2.2 INTERFACE DESCRIPTION
D-SUB 15 PIN CONNECTOR
15
610
11 15
SIGNAL LEVEL
Pin Number Pin Function
1 Red video input
2 Green video input
3 Blue video input
4 No Connection
5 Ground
6 Red video ground
7 Green video ground
8 Blue video ground
9 +5V
10 H/V sync ground
11 No connection
12 (SDA)
13 Horizontal sync (Composite sync)
14 Vertical sync
15 (SCL)

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DVI-D 24 PIN CONNECTOR
Pin No. Signal Name Description
1 RX2- TMDS negative differential input, channel 2
2 RX2+ TMDS positive differential input, channel 2
3 GND Logic Ground
4 Reserved 4 Reserved. No connection
5 Reserved 5 Reserved. No connection
6 DDC-CLK DDC2B Clock
7 DDC-DAT DDC2B Data
8 Reserved 8 Reserved. No connection
9 RX1- TMDS negative differential input, channel 1
10 RX1+ TMDS positive differential input, channel 1
11 GND Logic Ground
12 Reserved 12 Reserved. No connection
13 Reserved 13 Reserved. No connection
14 VCCX Power
15 GND Logic Ground
16 SENS 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 Reserved 20 Reserved. No connection
21 Reserved 21 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. Front Panel Function Controls And Indicators
Mute：Audio Mute button turns the sound off
Volume+/ Volume-：Decreases or increases volume
Button 1：Scrolls through menu options and adjusts the displayed
control. Also a shortcut to display the Contrast adjustment control
screen.
[▲]、[▼]：Displays the control screen for the highlighted control. Also
toggles between two controls on some screens. Also a shortcut to toggle
analog and digital connection.
Button 2：Displays the control screen for the highlighted control. Also toggles
between two controls on some screens. Also a shortcut to toggle analog and
digital connection.
Power：Standby Power On/Off
Power LED (Front Head)
Green – ON
Orange – Active Off
Dark = Soft Power Switch OFF

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Do the following to adjust the display setting:
1. To display the Main Menu, press button [1].
NOTE: All OSD menus and adjustment screens disappear automatically after about 15
seconds. This is adjustable through the OSD timeout setting in the setup menu.
2. To select a control to adjust, press or ▼to ▲scroll up or down in the Main Menu.
3. After the desired control is selected, press button [2]. A control screen like the one
shown below appears.
The command line at the bottom of the control
screen tells what to do next from this screen.
You can toggle between control screens,
adjust the selected option, or exit the screen.
4. To adjust the setting, press the up ▼or ▲down T buttons.
5. To save the adjustments and exit the menu, press button [1] twice.
The following tips may help you optimize your display:
• Adjust the computer's graphics card so that it outputs a 1280 x 1024 @ 60Hz video
signal to the LCD display. (Look for instructions on “changing the refresh rate” in the
graphics 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 display.)

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Main Menu Controls
Adjust the menu items shown below by using the up and down buttons.
Control Explanation
Auto Image Adjust sizes and centers the screen image automatically.
Contrast adjusts the difference between the image background (black level)
and the foreground (white level).
Brightness adjusts background black level of the screen image.
Input Select allows the user to toggle between an analog and a digital signal.
Audio Adjust
Volume increases the volume, decreases the volume, and mutes the audio.
Mute temporarily silences audio output.
Color Adjust provides several color adjustment modes, including preset color
temperatures and a User Color mode which allows independent adjustment of
red (R), green (G), and blue (B). The factory setting for this product is 6500K
(6500 Kelvin).
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.
5400K-Adds green to the screen image for a darker color.
User Color Individual adjustments for red (R), green (G), and blue (B).
1. To select color (R, G or B) press button [2].
2. To adjust selected color, press ▼and ▲.
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.

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Information displays the timing mode (video signal input) coming from the
graphics card in the computer, the LCD model number, the serial number, and
the ViewSonic®website URL. See your graphics card’s user guide for
instructions on changing the resolution and refresh rate (vertical frequency).
NOTE: VESA 1280 x 1024 @ 60Hz (recommended) means that the resolution
is 1280 x 1024 and the refresh rate is 60 Hertz.
Manual Image Adjust Sub-menu
H. Size (Horizontal Size) adjusts the width of the screen image.
H./V. Position (Horizontal/Vertical Position) moves the screen image left or
right and up or down.
Fine Tune sharpens the focus by aligning text and/or graphics with pixel
boundaries.
NOTE: Try Auto Image Adjust first.
Sharpness adjusts the clarity and focus of the screen image.

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Setup Menu displays the menu shown below:
Language Select allows the user to choose the language used in the menus
and control screens.
Resolution Notice allows the user to enable or disable this notice.
If you enable the Resolution Notice shown above and your computer is set at
a resolution other than 1280 x 1024, the following screen appears.
OSD Position allows the user to move the OSD menus and control screens.
OSD Timeout sets the length of time the OSD screen is displayed. For
example, with a “30 second” setting, if a control is not pushed within 30
seconds, the display screen disappears.
OSD Background allows the user to turn the OSD background On or Off.
Memory Recall returns the adjustments back to factory settings if the display
is operating in a factory Preset Timing Mode listed in the Specifications of this
manual.

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SHORT CUTS FUNCTION FROM THE BUTTONS
[1] Main Menu
[2] Input toggle (Analog or Digital).
[▼] or [▲] To immediately activate Contrast menu. It should be
change to Brightness OSD by push button [2]
[▼] + [▲] recall both of Contrast and Brightness to default
[;+] or [;-] To immediately activate Volume menu for audio volume.
[;+] + [;X] Recall volume to default
[1] + [2] toggle 720x400 and 640x400 mode when input 720x400
or 640x400 mode
[1] + [;X] White Balance. (Not shown on user’s guide)
[2] + [▼]
• Power Button Lock: Press and hold “[2], & ▼” for 10
seconds. If the power button is pressed the message
Power Button Locked will display for 5 seconds. With or
without this setting, after a power failure, your LCD
display’s power will automatically turn ON when power is
restored.
• Power Button Unlock: Press and hold “[2], & ▼” again
for 10 seconds.
[1] + [▲]
• OSD Lock: Press and hold "[1], & (▲)" for 10 seconds.
If any buttons are pressed the message OSD Locked will
display for 5 seconds.
• OSD Unlock: Press and hold “[1], & ▲” again for 10
seconds.
Remark : All the short cuts function are only available while OSD off

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4. Circuit Description
4.1 LCD MONITOR DESCRIPTION
The LCD MONITOR will contain a Main Board, an Power Board, Key Board which
house the flat panel control logic, brightness control logic and DDC.
4.2 MAIN BOARD BLOCK FUNCTION DESCRIPTION
The main board contains panel control logic, brightness control logic, DDC and DC
convert DC circuit and so on.
Power Board
(Include: adapter, inverter)
Flat Panel and
CCFL backlight
Main Board
Key Board
RS232 Connector
For white balance
adjustment in factory
mode
HOST Computer
CCFL Drive.
AC-IN
100V-240V
Video signal, DDC
Monitor Block Diagram
R
G
B
H
V
SDA
SCL
OSC
Backlight and Panel
PWPC board
EPROM EPROM Keyboard
TSUM56AK

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4.3 PWPC BOARD BLOCK FUNCTION DESCRIPTION
PWPC board combines to adapter and inverter, Adapter which commonly consists
of bridge rectifier and filter, start circuit, PWM control circuit, protection circuits and
convert to 12V, 5V DC voltage by input 90V-240V AC voltage that provide power supply
for each chips in the main board and inverter. Inverter is DC TO AC circuit. It changes
the 12v DC of power supply to about 600-800v AC that drives the backlight. It mostly
consists of starting circuit, PWM controller, DC changing circuit, LC surging circuit,
output circuit and protection circuit etc.
AC input EMI filter
Bridge
Rectifier
and Filter
Start Circuit
R903, R904,R905
PWM
Control IC
Over
Voltage
Protect
Rectifier
CMOS
ON/OFF
Control
PWM
Control IC
Feedback
Circuit
OSC and
Output
Circuit
DC Convert
Circuit
MOSFET
Q203
Over
Voltage
CN902
Transformer
Lamp
5V
12V
ON/OF
DIM

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4.4 INTRODUCTION OF IC
STUM56AK(U401): integrate ADC, OSD, SCALER, MCU, LVDS, convert analog RGB
into digital and room and shrink scaling output to LCD panel.
PIN Function:
AIC1084-33PM (U702): DC power convert, used to 5v convert 3.3v.
LT1117-18(U701): DC power convert, used to 5v convert 3.3v.
Pin Symbol Description
70 SDO SPI flash serial data output; Input w/5V-tolerant
71 CSZ SPI flash chip select; output
72 SCK SPI flash serial select; output
73 SDI SPI flash serial data input; output
65 DDCA_SDA/RS232_TX DDC data for analog interface; 4mA driving
strength/UART transmitter/GPIO; I/O w/5V-tolrant
66 DDCA_SDA/RS232_RX DDC data for analog interface/UART
transmitter/GPIO;Input w/5V-tolrant
36 DDCD_SDA DDC data for DVI interface; 4mA driving strength;
I/O w/5V-tolerant
37 DDCD_SCL DDC clock for DVI interface; Input w/5V-tolerant
19 RST Chip reset; High reset; Input w/5V-tolerant
22 RSTN Chip reset; Low reset; Input w/5W-toerant
11 VCTRL Regulator control; Output
63 HSYNCO Analog HSYNC input
64 VSYNCO Analog VSYNC input
62 REFP Internal ADC top de-coupling pin
61 REFM Internal ADC bottom de-coupling pin
51 REXT
External resistor 390 ohm to AVDD＿DVI
21 PWM1 PWM1; 4mA driving strength; Output
29 PWM0 PWM0; 4mA driving strength; Output
4 BYPASS For External Bypass Capacitor
33 XIN Xin; Crystal Oscillator Input
34 XOUT Xout; Crystal Oscillator Output
44、50 AVDD＿DVI DVI Power 3.3V
60 AVDD＿ADC ADC Power 3.3V
52 AVDD＿PLL PLL Power 3.3V
34 AVDD＿MPLL MPLL Power 3.3V
14、67、95、
103、115 VDDP Digital Output Power 3.3V
13、38、41、
47、96、116
VDDC Digital Core Power 1.8V

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TPA3003D2 (U601): The TPA3003D2 is a audio amplifier IC,3-W efficient, driving
speakers as low as 8 , range of gain from -40dB to 36 dB. The function of
each pin and the inside circuit diagram are as follows:
Circuit Diagram

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PIN Function
TERMINAL
NO. NAME I/O DESCRIPTION
AGND 9,10,26 - Analog ground for digital/analog cells in core
AVcc 33 - High-voltage analog power supply (8.5V to 14V)
AVDD 29 O 5-V Regulated output
AVDDREF 7 O 5-V Reference output-provided for connection to adjacent VREF terminal.
BSLN 13 I/O Bootstrap I/O for left channel, negative high-side FET
BSLP 24 I/O Bootstrap I/O for left channel, positive high-side FET
BSRN 48 I/O Bootstrap I/O for right channel, negative high-side FET
BSRP 37 I/O Bootstrap I/O for right channel, positive high-side FET
COSC 28 I/O I/O for charge/discharging currents onto capacitor for ramp generator triangle wave
biased at V2P5
FADE 30 I
Input for controlling volume ramp rate when cycling SD or during power-up. A logic
low on this pin places the amplifier in fade mode. A logic
high on this pin allows a quick transition to the desired volume setting.
LINN 6 I Negative differential audio input for left channel
LINP 5 I Positive differential audio input for left channel
LOUTN 16,17 O Class-D 1/2-H-bridge negative output for left channel
LOUTP 20,21 O Class-D 1/2-H-bridge positive output for left channel
MUTE 34 I A logic high on this pin disables the outputs. A low on this pin enables the outputs.
NC 31,32,35 - Not internally connected
PGNDL 18,19 - Power ground for left channel H-bridge
PGNDR 42,43 - Power ground for right channel H-bridge
PVVCCL 14,15 - Power supply for left channel H-bridge(tied to pins 22 and 23 internally), not
connected to PVCCR or AVcc
PVVCCL 22,23 - Power supply for left channel H-bridge(tied to pins 14 and 15 internally), not
connected to PVCCR or AVcc
PVCCR 38,39 - Power supply for right channel H-bridge(tied to pins 46 and 47 internally), not
connected to PVCCL or AVcc
PVCCR 46,47 - Power supply for right channel H-bridge(tied to pins 38 and 39 internally), not
connected to PVCCL or AVcc
REFGND 12 - Ground for gain control circuitry. Connect to AGND. If using a DAC to control the
volume, connect the DAC ground to this terminal.
RINP 3 I Positive differential audio input for right channel
RINN 2 I Negative differential audio input for right channel
ROSC 27 I/O Current setting resistor for ramp generator. Nominally equal to 1/8*Vcc
ROUTN 44,45 O Class-D 1/2-H-bridge negative output for right channel
ROUTP 40,41 O Class-D 1/2-H-bridge positive output for right channel
SD 1 I Shutdown signal for IC (low=shutdown, high=operational). TTL logic levels with
compliance to Vcc.
VCLAMPL 25 - Internally generated voltage supply for left channel bootstrap capacitors.
VCLAMPR 36 - Internally generated voltage supply for right channel bootstrap capacitors.
VOLUME 11 I DC voltage that sets the gain of the amplifier.
VREF 8 I Analog reference for gain control section.
V2P5 4 O 2.5-V Reference for analog cells, as well as reference for unused audio input when
using single-ended inputs.