Viewsonic VA702-2 Service Manual

Service Manual

ViewSonic VA702-2

VA721-3

VA721b-3

Model No. VS10781-2

VS10781-3W

17” Color TFT LCD Display

(VA702-2_VA721-3_VA721b-3_SM Rev. 1a Mar. 2006)

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

Copyright

Copyright © 2006 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 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.

Revision History

	Revision	SM Editing Date	ECR Number	Description of Changes	Editor
	1a	03/06/2006		Initial Release	Jamie Chang

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TABLE OF CONTENTS

1.	Precautions and Safety Notices	1
2.	Specification	3
3.	Front Panel Function Control Description	11
4.	Circuit Description	14
5.	Adjustment Procedure	25
6.	Troubleshooting Flow Chart	30
7.	Recommended Spare Parts List	38
8.	Exploded Diagram and Exploded Parts List	43
9.	Block Diagram	47
10.	Schematic Diagrams	48
11.	PCB Layout Diagrams	56

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1. Precautions and Safety Notices

SAFETY PRECAUTIONS

This monitor is manufactured and tested on a ground principle that a user’s safety comes first. However, improper used or installation may cause damage to the monitor as well as to the user.

WARNINGS:

•This monitor should be operated only at the correct power sources indicated on the label on the rear of the monitor. If you’re unsure of the power supply in you residence, consult your 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 by yourself, as it contains no user-serviceable parts. Only the qualified technician can repair it.

•Do not remove the monitor cabinet. There are high-voltage parts inside that may cause electric shock to human bodies.

•Stop using the monitor if the cabinet is damaged. Have it checked by a service technician.

•Put your monitor only in a lean, cool, dry environment. If it gets wet, unplug the power cable immediately and consult your closed dealer.

•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.

•Do not place heavy objects on the monitor or power cord.

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 voltage, 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.

SERVICE NOTES

•When replacing parts or circuit boards, clamp the lead wires around terminals before soldering.

•Keep wires away from high voltage, high temperature components and sharp edges.

•Keep wires in their original position so as to reduce interference.

•Adjustment of this product please refers to the user’manual.

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Handling and Placing Methods

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2. Specification

1. INTPRODUCTION

	FEATURES		VA702-2
	Size		17 “
	Luminance (Typ)		300 cd/
	Contrast Ratio (Typ)		500:1
TFTLCD PANEL
	Colors (6 bits + 2 bits FRC)		16.2 M
	Response Time (Typ)		8 ms
	Viewing Angle (H/V)		140 ° / 130 °
	Recommend resolution		1280x1024@60Hz
Input Signal	Analog (75ohms, 0.7/1.0 Vp-p)		Yes
	Digital		No
	Separate Sync		Yes
Sync Compatibility
	Composite Sync		No
	Sync on Green		No
	PC		Yes
Compatibility
	Power Mac		Yes
	TV Box (NextVision 6)		Yes
Power Voltage	AC 100-240V, 50/60Hz		Yes
Power	On Mode(Max / Typ)		36 W
Consumption	Off Mode (Max)		1 W
Audio			No
	Tilt ( 20 ° - -5 °)		Yes
Ergonomics	Swivel		No
	Pivot		No
	Height Adjust		No
OSD Control	[ 1 ] [▼] [▲] [ 2 ] [ ]		Yes
Dimension	Physical (W x H x D)		378 x 374 x 196 mm
	Package (W x H x D)		440 x 511 x 132 mm
Weight	Physical (Net Weight)		4.5 kg
	Package (Gross Weight)		6.2 kg
Operating	Temperature ( / )		32 -104 / 0 -40
Condition
	Humidity (%)		10 % - 90 %
Storage Condition	Temperature ( / )		-4 -140 / -20 -60
	Humidity (%)		5 % - 90 %
	UL, cUL, FCC-B, CB, CE, ENERGY, NOM, TUV/GS, TUV ERGO
	(covers ISO13406-2 & MPRII), TCO’99 (VA702b), TCO’03
Regulation	(VA702), GOST-R+20 ORIGINAL		COPIES HYGIENIC, SASO,
	PCBC, VCCI, BSMI, CCC, (PSB), (C-TICK), TUV-S, Green Mark,
	Energy Star

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		FEATURES				VA721-3 / VA721b-3
		Size				17 “
		Luminance (Typ)				300 cd/
	TFTLCD PANEL	Contrast Ratio (Typ)				500:1
		Colors (6 bits + 2 bits FRC)				16.2 M
		Response Time (Typ)				8 ms
		Viewing Angle (H/V)				150 ° / 135 °
		Recommend resolution				1280x1024@60Hz
	Input Signal	Analog (75ohms, 0.7/1.0 Vp-p)				Yes
		Digital				No
	Sync Compatibility	Separate Sync				Yes
		Composite Sync				No
		Sync on Green				No
	Compatibility	PC				Yes
		Power Mac				Yes
		TV Box (NextVision 6)				Yes
	Power Voltage	AC 100-240V, 50/60Hz				Yes
	Power	On Mode(Max / Typ)				35 W (Max)
	Consumption	Off Mode (Max)				1 W
	Audio					No
		Tilt ( 20 ° -5 °)				Yes
	Ergonomics	Swivel				No
		Pivot				No
		Height Adjust				No
	OSD Control	[ 1 ] [▼] [▲] [ 2 ] [ ]				Yes
	Dimension	Physical (W x H x D)				378 x 374 x 196 mm
		Package (W x H x D)				440 x 511 x 132 mm
	Weight	Physical (Net Weight)				4.5 kg
		Package (Gross Weight)				6.2 kg
	Operating	Temperature ( / )				32 -104 / 0 -40
	Condition	Humidity (%)				10 % - 90 %
	Storage Condition	Temperature ( / )				-4 -140 / -20 -60
		Humidity (%)				5 % - 90 %
		UL/cUL, FCC-B, CB, CE, ENERGY, NOM, TUV/GS, TUV ERGO
	Regulation	(covers ISO13406-2 & MPRII), TCO’03, GOST-R+20 ORIGINAL
		COPIES HYGIENIC, SASO, PCBC, VCCI, BSMI, CCC, (PSB),
		(C-TICK), TUV-S, Green Mark, Energy Star
2 GENERAL specification
	Test Resolution & Frequency			1280x1024 @ 60Hz
	Test Image Size			Full Size
	Contrast and Brightness Controls			Factory Default:
				Contrast = 70%, Brightness = 100%

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3		VIDEO INTERFACE
		Analog Input Connector		DB-15 (Analog), refer the appendix A
		Video Cable Strain Relief		Equal to twice the weight of the monitor for five
				minutes
		Video Cable Connector DB-15 Pin out		Compliant DDC 1/2B
		Video Signals		Video RGB (Analog) - Separate
		Video Impedance		75 Ohms (Analog)
		Maximum PC Video Signal		950 mV with no damage to monitor
		Maximum Mac Video Signal		1250 mV with no damage to monitor
		Sync Signals		LVDS
		DDC 1/2B		Compliant with Revision 1.3
		Sync Compatibility		Separate Sync
		Video Compatibility		Shall be compatible with all PC type	computers,
				Macintosh computers, and after market	video cards
				640 x 350, 640 x 480, 720 x 400 (640 x 400*), 800 x
		Resolution Compatibility		600, 832 x 624, 1024 x 768, 1152 x 870, 1280 x 720,
				1280 x 1024
		Exclusions		Not compatible with interlaced video
4		POWER SUPPLY
		Internal Power Supply		Part Number: ILIPI-004
		Input Voltage Range		90 to 264 VAC
		Input Frequency Range		47.5 to 63 Hertz
		Short Circuit Protection		OUTPUT CAN BE SHORTED WITHOUT
				DAMAGE
		Over Current Protection		2.4 A TYPICAL AT 14.2 VDC
		Leakage Current		3.5MA (MAX) AT 254VAC / 60HZ
		Efficiency		80% TYPICAL AT 115VAC FULL LOAD
		Fuse		INTERNAL AND NOT USER
				REPLACEABLE
		Power Dissipation		35 WATTS (TYP)
		Max Input AC Current		0.8 ARMS @ 90VAC, 0.4 ARMS @265VAC
		Inrush Current (Cold Start)		30 A @ 120VAC, 50 A (MAX) @ 220VAC
				Shall start and function properly when under
		Power Supply Cold Start		full load, with all combinations of input
				voltage, input frequency, and operating
				temperature
				Shall be able to withstand an ansi/ieee
		Power Supply Transient Immunity		c62.41-1980 2000v 200 ampere ring wave
				transient test with no damage
		Power Supply Line Surge Immunity		Shall be able to withstand 1.5 times nominal
				line voltage for one cycle with no damage
				Shall be able to function properly, without
		Power Supply Missing Cycle Immunity		reset or visible screen artifacts, when ½
				cycle of AC power is randomly missing at
				nominal input
		Power Supply Acoustics		The power supply shall not produce audible
				noise that would be detectable by the user.

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			Audible shall be defined to be in compliance
			with ISO 7779 (DIN EN27779:1991) Noise
			measurements of machines acoustics.
			Power Switch noise shall not be considered
			Separate 3-prong NEMA 5-15P type plug.
	US Type Power Cable		Length = 1.8m. Connects to display.
			Color = Black
			Schuko CEE7-7 type plug.
	European Type Power Cable		Length = 1.8m, Connects to display.
			Color = Black
			Separate 3-prong type plug.
	CCC Type Power Cable		Length = 1.8m. Connects to display.
			Color = Black
			Separate 2-prong NEMA 1-15P type plug.
	PSE Type Power Cable		Length = 1.8m. Connects to display.
			Color = Black
	Power Saving Operation(Method)		VESA DPMS Signaling
	Power Consumption		On Mode < 36 W (max)
			Off Mode< 1W
	Recovery Time		On Mode = N/A, Active Off < 3 sec
5 ELECTRICAL REQUIREMENT
Horizontal / Vertical Frequency
	Horizontal Frequency		30 – 82 kHz
	Vertical Refresh Rate		50 – 85* Hz.
			* When the resolution is set to 1280 x 1024, the vertical refresh
			rate may be up to 75 Hz; for all other resolutions, the vertical
			refresh rate may be up to 85Hz.
	Maximum Pixel Clock		140 MHz
	Sync Polarity		Independent of sync polarity.
Timing Table
	Item	Timing			Analog
	1	640 x 350 @ 70Hz, 31.5kHz			Yes
	2	640 x 400 @ 60Hz, 31.5kHz			Yes
	3	640 x 400 @ 70Hz, 31.5kHz			Yes
	4	640 x 480 @ 50Hz, 24.7kHz			Yes
	5	640 x 480 @ 60Hz, 31.5kHz			Yes
	6	640 x 480 @ 67Hz, 35.0kHz			Yes
	7	640 x 480 @ 72Hz, 37.9kHz			Yes
	8	640 x 480 @ 75Hz, 37.5kHz			Yes
	9	640 x 480 @ 85Hz, 43.27kHz			Yes
	10	720 x 400 @ 70Hz, 31.5kHz			Yes
	11	800 x 600 @ 56Hz, 35.1kHz			Yes
	12	800 x 600 @ 60Hz, 37.9kHz			Yes
	13	800 x 600 @ 75Hz, 46.9kHz			Yes
	14	800 x 600 @ 72Hz, 48.1kHz			Yes
	15	800 x 600 @ 85Hz, 53.7kHz			Yes
	16	832 x 624 @ 75Hz, 49.7kHz			Yes
	17	1024 x 768 @ 60Hz, 48.4kHz			Yes
	18	1024 x 768 @ 70Hz, 56.5kHz			Yes
	19	1024 x 768 @ 72Hz, 58.1kHz			Yes
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20	1024 x 768	@ 75Hz, 60.0kHz		Yes
21	1024 x 768	@ 85Hz, 68.67kHz		Yes
22	1152 x 870 @ 75Hz, 68.7kHz			Yes
23	1280 x 1024		@ 60Hz, 63.4kHz	Yes
24	1280 x 1024		@ 75Hz, 79.97kHz	Yes
25	1280x 720 @ 60Hz, 45kHz (HDTV)			Yes

Primary Presets

1280x1024 @ 60Hz

User Presets

Number of User Presets (recognized timings) Available: 10 presets total in FIFO configuration

Changing Modes

●Maximum Mode Change Blank Time for image stability: 3 seconds (Max), excluding “Auto Image Adjust” time.

●Under DOS mode (640 x 350, 720 x 400 & 640 x 400), it should recall factory setting when

execute “Auto Image Adjust”.

The monitor needs to do “Auto Image Adjust” the first time when a new mode is detected. (See section “0-Touch™ Function Actions”)

6 FRONT PANEL CONTROLS AND INDICATORS

Front Panel Hardware Controls

	Power Switch (Front Head)		Power Control, soft Power Switch.
	Power LED (Front Head)		Green – ON
			Orange – Active Off
			Dark = Soft Power Switch OFF
	Front Panel Controls (Head)		[ ] Power
	[ ] [ 1 ] [ 2 ] [▲] [▼]		[ 1 ] BUTTON 1
			[ 2 ] Button 2
			[▲] UP ARROW BUTTON
			[▼] DOWN ARROW BUTTON
			Note: Power Button, Button 1 and Button 2
			must be one-shot logic operation. (i.e. there
			should be no cycling)
	Reaction Time		OSD must fully appear within 0.5s after
			pushing Button 1
Short Cuts Function from the button(s)
	[1]	Main Menu
	[2]	Auto Image Adjust
	[▼] 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
	[1] + [2]	Toggle 720x400 and 640x400 mode when input 720x400
		or 640x400 mode
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[1] + [▼] + [▲]	White Balance. (Not shown on user’s guide)
[1] + [▼]	Power Lock
[1] + [▲]	OSD Lock

Remark : All the short cuts function are only available while OSD off

Main Menu Controls

Auto Image Adjust

Contrast/Brightness*1*3

Color Adjust

SRGB, 9300K, 6500K(default), 5400, User Color [R, G, B]

Information [H Frequency, V Frequency, Pixel Clock, Resolution, Serial Number, Model Number, “www.ViewSonic.com” ]

Manual Image Adjust [H. Size, H. Position, V. Position, Fine Tune, Sharpness*2

Setup Menu

Language [English, French, German, Italian, Spanish, Finnish, Japanese, Traditional Chinese, Simplified Chinese]

Resolution Notice, OSD Position, OSD Timeout, OSD Background

Memory Recall

*1 These functions are not available under SRGB Mode

*2 These functions are not available under Native Resolution Mode

*3 These function settings can be set to default value by pressing [▼]+[▲]

[Remark] Please refer to the detail in the Appendix C

Function descriptions

OSD Lock short cuts function for the buttons

The OSD lock will be activated by pressing the front panel control buttons "(1), & (▲)" for 10 seconds. If the user then tries to access the OSD by pressing any of the buttons "1", "▼", "▲", "2" a message will appear on the screen for 3 seconds showing "OSD Locked". The OSD lock will be deactivated by pressing the front panel control buttons "(1), & (▲)" again for 10 seconds.

Note1: When the OSD is locked will lock all functions, including “Volume” and “Mute” Note 2: Status bar indicating OSD Lock or Unlock is in progress and when complete it will indicate “OSD Locked”

Note 3: OSD Lock should not lock Power Button and Power Lock function

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Power Lock short cuts function for the buttons

The power button lock will be activated by pressing the front panel control buttons "(1), & (▼)" for 10 seconds. Locking the power button means that the user won't be able to turn off the LCD while the power button is locked. If the user presses the power button while it is locked, a message will appear on the screen for 3 seconds showing "Power Button Locked". It also means that with the power button locked, the LCD would automatically turn back "On" when power is restored after a power failure. If the power button is not in the locked mode, then power should return to its previous state when power is restored after a power failure. The power button lock will be deactivated by pressing the front panel control buttons "(1), & (▼)" again for 10 seconds.

Note 1: Status bar indicating Power Button lock or unlock is in progress and when complete it will indicate “Power Button Locked”

Note 2: Power should only be lockable in the “On State”

Memory Recall Actions

Memory Recall action on the analog and digital mode as below

1.Recall white balance to factory setting

2.Set the factory defaults as shown in Section 4-8

3.Clean all the mode setting buffer

4.Execute Auto Image Adjust

Note: Memory Recall cannot effect at Language, Power Lock and User Color Settings

Resolution Notice Actions

1.Resolution Notice OSD should show on screen after changing to non-native mode for 30 sec

2.The OSD should disappear after 10 sec or by pushing button [1] or [2]

Resolution Notice function should be disabled when push button [2] under Resolution Notice OSD

0-Touch™ Function Actions

1.Execute Auto Image Adjust when new mode detected, and save the settings to buffer for further use

2.It should be reset by Memory Recall function

(Should not reset by power off, power unplug and others)

OSD Auto Save

The OSD shall save new settings when it is turned off by the user or when it times out. There shall not be a separate save

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3. Front Panel Function Control Description

1.	Key Function Description
		CONTROL KEY		KEYS FUNCTION
		[AUTO] [2]		By pressing [AUTO] key, “Auto Image Adjust” is performed
		[MENU] [1]		By pressing [MENU] key, Main menu display
				A. When “MENU OSD” display, press these keys to change the contents of
		[▼] [▲]		an adjustment item, or change an adjustment value
				B. When “MENU OSD” is un-display, press these keys to change brightness
				and contrast
		[POWER]		Power on or power off the monitor
2.	Hot Key Operation
		CONTROL KEY	KEYS FUNCTION
		[▼] + [▲]	Recall Contrast or Brightness while in the Contrast or Brightness adjustment,
			or recall both of Contrast and Brightness when the OSD is not open.
	[1] + [2]		Toggle 720x400 and 640x400 mode when input 720x400 or 640x400 mode.
		[1] + [▼] + [▲]	White Balance (Not shown on user’s guide)
		[1] + [▼]	Power Lock
		[1] + [▲]	OSD Lock

Remark : All the short cuts function are only available while OSD off

3. OSD Control
3.1 OSD table
	Layer 1	Layer 2		Layer 3
	Auto Image Adjust
	Contrast/Brightness	Contrast (+ / -)
		Brightness (+ / -)
		Srgb
		9300K
		6500K
	Color Adjust	5400K
				Red (+ / -)
		User Color
				Green (+ / -)
				Blue (+ / -)
	Information
	Manual Image Adjust	H/V Position		H Position (+ / -)
				V Position (+ / -)
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					H Size	+ / -
					Fine Tune	+ / -
					Sharpness	+ / -
						English
						French
						German
						Italian
					Language Select
						Spanish
						Finnish
	Setup Menu					Japanese
						Simplified Chinese
						Traditional Chinese
					Resolution Notice	On/Off
					OSD Position	H Position (+ / -)
						V Position (+ / -)
					OSD Time Out
					OSD Background	On/Off
	Memory Recall
3.2 OSD lock Menu function
					OSD Lock Menu Function Check
		Item		Method		Phenomenon
						Press any of buttons"1", "▼",
		Activate OSD lock		[1] + [▲] 10S		"▲", "2" will appear "OSD
						Locked" 3s
		Deactivate OSD lock:		[1] + [▲] 10S(again)
		NOTICE:
		When the OSD is locked will lock all functions.
		Status bar indicating OSD Lock or Unlock is in progress and when complete it will indicate
		“OSD Locked”
		OSD Lock should not lock Power Button and Power Lock function

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3.3 Power lock Menu function

		Power Lock Menu Function Check
	Item	Method	Phenomenon
	Activate Power Lock		Can not turn off the LCD;
			Press the power button will
			appear "Power Button Locked"
		[1] + [▼] 10S	OSD 3s;
			LCD would automatically turn
			back "On" when power is
			restored after a power failure
	Deactivate Power	[1] + [▼] 10S(again)
	Lock
	NOTICE:
	Status bar indicating Power Button lock or unlock is in progress and when complete it will
	indicate “Power Button Locked”
	Power should only be lockable in the “On State”
3.4 Resolution notice function
		Resolution Notice Menu
	Item	Method	Phenomenon
		Resolution Notice OSD should
	Activate Resolution	show on screen after changing
		to non-native mode for 30 sec,	------
	Notice Menu
		And it should disappear after 10s
		or by pushing button [1] or [2]
	Deactivate	Push button [2] under Resolution
	Resolution Notice		-------
		Notice OSD, select Disable
	Menu

3.5 Factory Mode Introduction

When input the signal, press “power key” to turn off the monitor. Press” [▼] +[▲] +[] “at the same time so as to enter factory mode. After power on, press ‘’Menu[1]’’key, you can see the Factory menu.

INL : Currently using panel model name

V2 050526	: Currently using firmware version information.
Auto Color	: Automatically calibrate chip ADC parameter by using chip internal DAC

Color Temperature : The R, G, B of 9300K and 6500K and 5400K and User Mode Colors are all generated from scaling back end.

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4. Circuit Description

4.1 Switching Mode Power Supply

4.1.1 AC Current Input Circuit

P801 is a connector for connecting AC Power. F801 is a fuse to protect all the circuit. AC input voltage is from 90V to 264V. R820 and R821 joined between two inputting main circuit to prevent man from shock. L801 is used to clear up low frequency wave. C801 and C806 are used to discharge the waves that L801 produced. High frequency waves are damped by C801 and C806. D801 is a rectifier which composed of 4 build-in diodes, it inverts AC to DC.

4.1.2High Voltage to Low Voltage Control Circuit

C805 is used to smooth the wave from rectifier. IC802 is a highly integrated PWM controller, which build-in a power MOSFET. When rectified DC high voltage is applied to the DRAIN pin during start-up, the MOSFET is off initially, and the CONTROL pin capacitor is charged through a switched high voltage current source connected internally between the DRAIN and CONTROL pins. When the CONTROL pin voltage Vc reaches approximately 5.8V, the control circuitry is activated and the soft-start begins. The soft-start circuit gradually increases the duty cycle of the MOSFET from zero to the maximum value over approximately 10ms. If no external feedback/supply current is fed into the CONTROL pin by the end of the soft-start, the high voltage current source is turned off and the CONTROL pin will start discharging in response to the supply current drawn by the control circuitry.

Resistor R803, R807, R824 and R825 are for line over voltage shut-down (OVP) and line under-voltage detection (UVP).Resistors R801, R805, R822, and R823 are for external current limit adjustment, and used to reduce the current limit externally to a value close to the operating peak current of primary about 1.35A. The mean is power will protected when the primary current over about 1.35A.

When PWM is turned off, the main current flow will be consumed through D804 and ZD802, This will prevent MOSFET which built-in IC802 from being damaged under large current impulse and voltage spike.

D806 and C815 provide internal Auxiliary current to CONTROL pin during normal operation. In addition, error amplifier and feedback current to the CONTROL pin are for duty cycle control.

4.1.3DC_5V and DC_14V Output Circuit

For DC 5V, D805 is used to rectify the inducted current. R806 and C811 are used to store energy when current is reversed. The parts including C812, C814, C822, C821, B801 and L803 are used to smooth the current waves.

For DC 14V, D803 is used to rectify the inducted current. R802 and C802 are used to store energy when current is reversed. The parts including C808, C810 and L802 are used to smooth the current waves.

4.1.4Feedback and OVP Protect Circuit

Pin R of IC803 is supplied 2.5V stable voltage. It is connected to 5V and 14V output through R811, R810 and R818. R811, R810 and R818 are output sampling resistor. When the sampling voltage more than 2.5V or less than 2.5V, feedback current of IC802 will change, this can change the voltage from transformer T801.

For 5VDC output OVP, ZD803 is a zener diode, when 5V output voltage becomes up to 5.6V, the

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zener current cause R819 voltage become up to 0.7V, Q801 is triggered and OVP starts. For 12VDC output OVP, ZD804 is a Zener Diode, when 14V output voltage becomes up to 16V, the zener current cause R819 voltage become up to 0.7V, Q801 is triggered and OVP starts. The collector current of Q801 is used to make build-in diode light. FB Current of IC802 will be changed; it can change the voltage from T801.

Q802, R827, R828 and ZD801 make up of dummy loading circuit. For start-up sequence, during 5V output take place high loading first, this dummy loading circuit operated to insure 14V not be increased.

4. 2 Inverter circuit

4.2.1Low voltage to high voltage circuit

12VDC supplies the power to IC501 through F501; the control signals that BRIGHTNESS and ON/OFF come from I/F board. ON/OFF signal connect to pin8 of IC501 and makes IC501 enabled. BRIGHTNESS is connected to pin7 of IC501 to adjust the panel luminance. R524, R529, C505 make up of a delay-time circuit and R528, R523, R524 make up of a voltage divided circuit. C504 is used to filter the high frequency noise. The operation frequency is determined by R522 and C529. For BURST MODE, its dimming frequency is determined by R527 and C506. C502 is used for soft start and compensation, C502, C528 are used to filter noise.

The output drives, including NDR4, NDRV2, PDRV3, PDRV1 (pins1, 3, 15, 16 respectively), generate a square pulses to drive MOSFET U501, U502. And U501, U502 works as full-bridge topology, it is high efficient, zero voltage switch.

During start up, VSEN (pin9) detects the voltage at the transformer secondary. When VSEN reaches 3.0V, the output voltage is regulated. If no current is detected for around 1.5 seconds, IC501 will shut down.

The current flowing through CCFL is detected and regulated through sense resistor R509, R511. The feedback voltage through R506, R507, and C508 connected to Pin11 (ISEN), and then compared with a reference voltage (1.5V) via a current amplifier, resulting in PWM drive outputs to full-bridge switches.

4.2.2Protection circuit

Over Voltage Protection: R501and R502 are connected in high voltage output connector, the divided AC voltage is inverted DC voltage through D508, R505 and C507are used to rectify wave & dump noise. Then the voltage signal reaches Pin9 VSEN of IC501, when the voltage changes, build-in PWM of IC501 will adjust output voltage.

Open Lamp Protection: In normal operation, the resistors R510, R511, R512, R509 are sensed a high level AC voltage, the AC signal IS1 invert DC voltage through D509, R515, C533, and the high level DC voltage reaches the gate pin of Q502, similarly, the gate pin of Q503, Q504, Q505 has high level DC voltage. So the gate pin of Q501 has a low level voltage, and the IC501 is normal operation. Once one of signal IS1, IS2, IS3, and IS4 is low, the voltages of Q501 gate pin is high level, and make the voltage of ISEN low level, the IC501 will shut down.

4.3I/F Board Circuit

4.3.1Power Input

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+5V is from the power board and supply for U101(FS8860-18PJ) U102(FS8860-33PJ) U105(MCU:W78E65P) and panel. +3.3V output is generated from +5V through C169 and C102 filtering, and U102 outputs. +3.3V is used for U104 (Scaler: TSU16AK). +1.8V output is generated from +5V through C169, C105 and C102 filtering, and U101 outputs. +1.8V is also used for U104. 4.3.2MCU (W78E65P)

VDD is +5V and its frequency of XTAL1 is 22.1184MHz. U105 #2 is defined as panel-enable. When the I/O port is low, Q101 and Q102 are conducted. And then after C109 and C110 filtering, obtain the voltage of VLCD, which will be connected to CN103. U105 #3 is defined as CCFL-enable. When the I/O port is low, Q103 is pulled up and the backlights are on; When the I/O port is high, Q103 is conducted and the backlights are off. U105 #4 is defined as DET-VGA, connected with CN102 #5. U105 #14, #36, #37, #38, #39, #40, #41, #42, #43 are the communications with U104 (Scaler), which are connected to #72, #31, #78, #77, #30, #70, #71, #69, #32 of Scaler. U105 #43 outputs reset signal to U104 (Scaler).

U106 is EEPROM used for saving EDID data, which is connected by SCL and SDA pins with #16 and #17 of MCU. Connect #12 to #26 of U105 for ISP.

4.3.3Scaler (TSU16AK)

The frequency of XTAL2 is 14.318MHz. U104 #1, #102-#103, #106-#113, #118-#125, #128 output LVDS digital data of 8 bit to panel control circuit through CN103. U104 #73 generates a PWM waveform by regulating the duty to control the brightness of the backlights. U104 #30-#32, #69-#72, #77-#78 are the communications with U105 (MCU) that are connected to #36-#43 of MCU. These communications include HWRESET, CSZ/ALE, SCL/RDZ, SDA/WRZ, and AD0-AD3.

4.3.4VGA Input

Signal R, G, B, SOG input through CN102 #1, #2, #3, and C115, C116, C117 and C118 filtering the high frequency noise. Signal HSYNC and VSYNC input through CN102 #13 and #14, and C119, R119, C120, R120 filtering. Then the analog signal enters U104, and then U104 deals with it internally. In addition, TVS101, TVS102, TVS103 (the three are BAV99), TVS104, TVS105, TVS106, TVS107 (they are constant voltage diode of 5V6) are ESD protector. Signal DDC-SCL inputs via CN102 #15, and then passes through TVS107 for ESD protection, goes into EDID EEPROM IC U103. Signal DDC-SDA inputs via CN102 #12, and then passes through TVS106 for ESD protection, goes into EDID EEPROM IC U103. CN102 #5 is defined as cable detect pin, this detector realizes via R107 and U105 #4. The PC-5V of U103 is supplied by PC via CN103 #9 with D103 for ESD protection, or supplied by Monitor self via D104.U103 is an EEPROM IC, which is a kind of memory and used for saving EDID data.

4.3.5Button Control

Button “Key-Power” is defined as power on/off, which is connected to U105 #24 through CN106 #4.

Button “Key-2” is defined as two functions of selecting and adjustment, which is connected to U105 #25 through CN106 #1.

Button “Key-Up” is defined as plus, which is connected to U105 #26 through CN106 #3. Button “Key-Down” is defined as minus, which is connected to U105 #27 through CN106 #5.

Button “Key-1” is defined as two functions of menu and exit, which is connected to U105 #28

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