ViewSonic Va1903wb2 Service Manual
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- 21 – ViewSonic Corporation Confidential - Do Not Cop VA1903wb/VA1903wm PIN Function LD7575 PS (IC901): The LD7575 is a current-mode PWM controller with excellent power-saving operation. The embedded over voltage protection, over load protection and the special green-mode control provide the solution for users to design a high performance power circuit easily and etc. The function of each pin and the inside circuit diagram are as follows:
- 22 – ViewSonic Corporation Confidential - Do Not Cop VA1903wb/VA1903wm PIN Descriptions: Pin Name Function 1 RT This pin is to program the switching frequency. By connection a resistor to ground to set the switching frequency. 2 COMP Voltage feedback pin(same as the COMP pin in UC384X), By connecting a photo-coupler to close the control loop and achieve the regulation. 3 CS Current sense pin, connect to sense the MOSFET current 4 GND Ground 5 OUT Gate drive output to drive the external MOSFET 6 VCC Supply voltage pin 7 NC Unconnected Pin 8 HV Connect this pin to positive of bulk capacitor to provide the startup current for the controller, when Vcc voltage trips the UVLO(on), this HV loop will be off to save the power loss on the startup circuit. Block Diagram OZ9938GN(IC801): The OZ9938 is high performance, cost-effective CCFL controller designed for driving large-size LCD applications requiring 2 to 6 CCFLs.PWM control, Has such functions as short-voltage protection, Over-voltage protection, over-current protection and etc. The function of each pin and the circuit diagram inside are as follows:
- 23 – ViewSonic Corporation Confidential - Do Not Cop VA1903wb/VA1903wm PIN Descriptions: Pin Names Description 1 DRV1 Drive output 2 VDDA Supply voltage input 3 TIMER Timing capacitor to set striking time and shutdown delay time 4 DIM Analog dimming or Internal LPWM dimming or external PWM pulse input for dimming function 5 ISEN Current sense feedback 6 VSEN Voltage sense feedback 7 OVPT Over-voltage/ over-current protection threshold setting pin 8 NC No connection 9 NC No connection 10 ENA ON/OFF control of IC 11 L C T Timing capacitor to set internal PWM dimming frequency and also a pin for analog dimming selection 12 SSECMP Capacitor for soft start time and loop compensation 13 CT Timing resistor and capacitor for operation and striking frequency 14 GNDA Ground for analog signals 15 DRV2 Drive output 16 PGND Ground for power paths
- 24 – ViewSonic Corporation Confidential - Do Not Cop VA1903wb/VA1903wm Block Diagram
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ViewSonic Corporation
Confidential - Do Not Cop VA1903wb/VA1903wm
5. Adjustment Procedure
5.1 ADJUSTMENT CONDITIONS AND PRECAUTIONS
1. Approximately 30 minutes should be allowed for warm up before proceeding.
2. Adjustments should be undertaken only on those necessary elements since most of them
have been carefully preset at the factory.
3. ESD protection is needed before adjustment.
5.2 MAIN ADJUSTMENTS
NO. FUNCTIONS DESIGNATION
1. White Balance Function Key
2. Geometry Function Key
5.3 ALIGNMENT PROCEDURES
Approximately 30 minutes should be allowed for warm up before proceeding
White-Balance adjustment.
1. Adjust of White Balance
1.)How to do the Chroma-7120 MEM .Channel setting
A、Reference to chroma 7120 user guide
B、Use “ SC” key and “ NEXT” key to modify xyY value and use “ID” key to modify the
TEXT description Following is the procedure to do white-balance adjust
2.)Setting the color temp. You want
A、MEM.CHANNEL9 ( 9300 color):
9300 color temp. parameter is Wx = 0.283 ±0.03;Wy = 0.298 ±0.03;
Y = 250 ±20 cd/m
2 ,
B、MEM.CHANNEL10 ( 6500 color):
6500 color temp. parameter is Wx = 0.313±0.03;Wy = 0.329 ±0.03;
Y = 260 ±20 cd/m2,
C、MEM.CHANNEL 11 ( 5400 color):
5400 color temp. parameter is Wx = 0.335±0.03;Wy = 0.350 ±0.03;
Y = 250 ±20 cd/m2,
D、MEM.CHANNEL10 ( SRGB color):
6500 color temp. parameter is Wx = 0.313±0.03;Wy = 0.329 ±0.03;
Y = 220 ±20 cd/m2,
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ViewSonic Corporation
Confidential - Do Not Cop VA1903wb/VA1903wm
3.)Into factory mode of VA1903wb/VA1903wm
A、First Power off, then press Switch 2 button along with press Power button will activate
the factory mode, then MCU will do AUTO LEVEL automatically. Meanwhile press
MENU the OSD screen will located at LEFT TOP OF PANEL.
4.)Bias adjustment :
Set the Contrast
to 70
Adjust the Brightness
to 100.
5.)Gain adjustment :
Move cursor to “-F-” and press MENU key
A、Adjust 9300 color-temperature
(1)、Switch the Chroma-7120 to RGB-Mode (with press “MODE” button )
(2)、Switch the MEM. channel to Channel 9 ( with up or down arrow on chroma 7120 )
(3)、The LCD-indicator on chroma 7120 will show x = 0.283 ±0.03, y =0.298 ±0.03,
Y = 250 ±20 cd/m
2
(4)、Adjust the RED of color1 on factory window until chroma 7120 indicator reached
the value R=100
(5)、Adjust the GREEN of color1 on factory window until chroma 7120 indicator reached
the value G=100
(6)、Adjust the BLUE of color1 on factory window until chroma 7120 indicator reached
the value B=100
(7)、Repeat above procedure ( item 4,5,6) until chroma 7120 RGB value meet the
tolerance =100±5
B、Adjust 6500 color-temperature
(1)、Switch the chroma-7120 to RGB-Mode (with press “MODE” button )
(2)、Switch the MEM .channel to Channel 10( with up or down arrow on chroma 7120 )
(3)、The LCD-indicator on chroma 7120 will show x = 0.313 ±0.03, y = 0.329 ±0.03, Y =
260 ±20 cd/m
2
(4)、Adjust the RED of color3 on factory window until chroma 7120 indicator reached
the value R=100
(5)、Adjust the GREEN of color3 on factory window until chroma 7120 indicator reached
the value G=100
(6)、Adjust the BLUE of color3 on factory window until chroma 7120 indicator reached
the value B=100
(7)、Repeat above procedure ( item 4,5,6) until chroma 7120 RGB value meet the
tolerance =100±5
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ViewSonic Corporation
Confidential - Do Not Cop VA1903wb/VA1903wm
C、Adjust 5400 color-temperature
(1) Switch the chroma-7120 to RGB-Mode (with press “MODE” button )
(2)、Switch the MEM .channel to Channel 11( with up or down arrow on chroma 7120 )
(3)、The LCD-indicator on chroma 7120 will show x = 0.335 ±0.03, y = 0.350 ±0.03, Y =
250 ±20 cd/m
2
(4)、Adjust the RED of color3 on factory window until chroma 7120 indicator reached the
value R=100
(5)、Adjust the GREEN of color3 on factory window until chroma 7120 indicator reached
the value G=100
(6)、Adjust the BLUE of color3 on factory window until chroma 7120 indicator reached
the value B=100
(7)、Repeat above procedure ( item 4,5,6) until chroma 7120 RGB value meet the
tolerance =100±5
D、Adjust SRGB color-temperature
(1)、Switch the chroma-7120 to RGB-Mode (with press “MODE” button )
(2)、Switch the MEM .channel to Channel 10( with up or down arrow on chroma 7120 )
(3)、The LCD-indicator on chroma 7120 will show x = 0.313 ±0.03, y = 0.329 ±0.03, Y =
220 ±20 cd/m
2
(4)、Adjust the RED of color3 on factory window until chroma 7120 indicator reached
the value R=100
(5)、Adjust the GREEN of color3 on factory window until chroma 7120 indicator reached
the value G=100
(6)、Adjust the BLUE of color3 on factory window until chroma 7120 indicator reached
the value B=100
(7)、Repeat above procedure ( item 4,5,6) until chroma 7120 RGB value meet the
tolerance =100±5
E、Press reset key and Turn the Power-button “off to on” to quit from factory mode.
2. Geometry
1).Set cross-hatch pattern and preset timing as timing table listed.
2).Change to each mode in turn and wait for the monitor finish auto-alignment and save
press before change to next mode.
3).Until all of modes are adjusted, exit OSD menu and press POWER OFF to exit factory
mode.
- 28 – ViewSonic Corporation Confidential - Do Not Cop VA1903wb/VA1903wm 5.4 Factory Defaults Item Defaults Item Defaults Contrast 70% Input Priority N/A Brightness 100% Resolution Notice On Color Temperature6500K Vo l u m e 50% (for VA1903wm only) Sharpness 100% Balance N/A OSD H. Position 50% Treble N/A OSD V. Position 50% Bass N/A OSD Time Out 15 720x400 / 640x400 720x400 OSD Background On 5.5 Function Test 1 Product: 19” LCD Monitor 2 Test Equipment: Color Video Signal & Pattern (or PC with SXGA resolution and a sound card) 3 Test Condition: Before function test and alignment, each LCD Monitor should be warmed up for at least 30 minutes with the following conditions: (a)In room temperature, (b) With full-white screen, RGB, and Black (c) With cycled display modes, 640*480 (H=43.27kHz, V=75Hz) 800*600 (H=53.7kHz, V=75Hz) 1024*768 (H=68.67kHz, V=75Hz) 1280*1024 (H=79.97kHz, V=75Hz) 1440*900 (H=70.6kHz, V=75Hz) 4 Test Display Modes & Pattern Compatible Modes Item Timing Analog 1 640 x 480 @ 60Hz, 31.5kHz Ye s 2 640 x 480 @ 75Hz, 31.5kHz Ye s 3 720 x 400 @ 70Hz, 31.5kHz Ye s 4 800 x 600 @ 56Hz, 35.1kHz Ye s 5 800 x 600 @ 60Hz, 37.9kHz Ye s 6 800 x 600 @ 72Hz, 48.1kHz Ye s 7 800 x 600 @ 75Hz, 46.9kHz Ye s 8 1024 x 768 @ 60Hz, 48.4kHz Ye s 9 1024 x 768 @ 70Hz, 56.5kHz Ye s 10 1024 x 768 @ 72Hz, 58.1kHz Ye s 11 1024 x 768 @ 75Hz, 60.0kHz Ye s 12 1280 x 1024 @ 60Hz, 48.4kHz Ye s 13 1280 x 1024 @ 75Hz, 60.0kHz Ye s 14 1440 x 900 @ 60Hz, 55.9kHz Ye s 15 1440 x 900 @ 75Hz, 70.6kHz Ye s
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ViewSonic Corporation
Confidential - Do Not Cop VA1903wb/VA1903wm
Function Test Display Pattern
Item Test Content Pattern Specification Remark
1 Frequency &
Tracking Fine Line Moire Eliminate visual wavy
noise. Figure 1
2 Contrast/Bright
ness 16 Gray Scale 16 gray levels sh should
be distinguishable. Figure 2
3 Boundary Horizontal&Vertical
Thickness Horizontal and Vertical
position of video should
be adjustable to be
within the screen frame. Figure 3
4 RGB Color
Performance RGB Color Intensities Contrast of each R, G,
B, color should be
normal. Figure
4,5,6
5 Screen
Uniformity &
Flicker Full White Should be compliant
with the spec. Figure 7
6 Dead
Pixel/Line White Screen & Dark
Screen The numbers of dead
pixels should be
compliant with the spec. Figure 7,8
7 White Balance White & Black Pattern The screen must have
the pure white and black
pattern, no other color. Figure 9
Fine Line Morie Pattern (Figure1) Gray Scale Pattern (Figure2)
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ViewSonic Corporation
Confidential - Do Not Cop VA1903wb/VA1903wm
Horizontal & Vertical Thickness Pattern R. Color Pattern (Figure 4)
(Figure 3)
G. Color Pattern (Figure 5) B. Color Pattern (Figure 6)
Full White Pattern (Figure 7) Dark Screen Pattern (Figure 8)