ViewSonic Vx2255wmb-2 Service Manual

							
Control Explanation
Resolution Notice allows the user to enable or disable this notice.
If you enable the Resolution Notice show n above and your computer is set at a 
resolution other than 1680 x 1050,  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 fa ctory settings if the display is 
operating in a factory Preset Timing Mode  listed in the Specifications of this 
manual.
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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. R801 and R802 joined 
between two inputting main circuit to prevent man from shock. L801 is used 
to clear up low frequency wave. C801  and C802 are used to discharge the 
waves that L801 produced. High frequency waves are damped by C801 and 
C802. 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
 
C804 is used to smooth the wave from rectifier. IC802 is a highly 
integrated PWM controller. When rectif ied DC high voltage is applied to the 
HV pin during start-up, the MOSFET Q804 is  initially off, and the Vcc pin 
capacitor is charged. When the Vcc pi n voltage reaches approximately 10V, 
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 4ms. If no exte rnal feedback/supply current is fed 
into the FB pin by the end of the soft-start, the current Setpoint will be above 
the fault level, FAULT flag is raised, if the FAULT duration exceeds 80ms, 
the output controller disable  Resistor R808, R809, R810, R811 are for line over voltage 
shutdown(OVP)  
When PWM is turned off, the main  current flow will be consumed 
through R804 and D802, This will  prevent MOSFET Q804 from being 
damaged under large current impulse and voltage spike. 
D803 and C807 to provide internal A uxiliary voltage to Vcc pin during 
normal operation. Otherwise, error amplif ier and feedback current input the 
FB pin for duty cycle control. 
 
4.1.3 DC_5V and DC_14V Output Circuit
 
For DC 5V, D805 is used to rectify the inducted current. R828 and C814 
are used to store energy when current  is reversed. The parts including C818, 
C822, C820,L803 are used to smooth the current waves.  For DC 14V, D803 is used to rec tify the inducted current. R827 and 
C813 are used to store energy when curre nt is reversed. The parts including 
C815, C817 and L802 are used to  smooth the current waves. 
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4.1.4 Feedback and OVP Protect Circuit 
Pin R of IC803 is supplied 2.5-v stab le voltage. It connects to 5V and 
14V output through R822, R823 and R824. R822, R823 and R824 are output 
sampling resistor. When the sampling voltage more than 2.5V or less than 
2.5V, current of FB IC802 will change, this can change the voltage from 
T801.   OVP Protect Circuit: When output is  overvoltage, the auxiliary winding 
voltage will be increased, when it reache s about 14V. Q803 is triggered . It 
makes the IC802 Pin 1 exceed 5V, then the IC802 output will be disabled.    Q801, R816, R817 and ZD803 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 
 
Power supply 5V then pass through R517 to IC501. The extra PWM pulse 
signal (BRIGHTNESS signal) input to control IC through R512, R514, C510, 
The LCT pin is set to a DC voltage  of 0.7V by using a resistor divider(R507, 
R516), change the duty of PWM pulse,  will regulate the lamp current. The 
ON/OFF voltage connect to pin10 of IC 501 through D501, R501,    A voltage of 
2V to pin10 of IC501 enables the IC a nd activates the striking timer. The 
SSTCMP pin of IC501 performs the soft f unction, the C511 set the time of SST. 
The operation frequency determined  by external capacitor C512, C521 and 
resistor R508 connected at CT pin  of IC501. C515 connect the TIMER pin of 
IC501, the capacitor to set striking time  and shunt down delay time. DRV!, DRV2 
output for power MOSFET U501, U502. 
OZ9938 provides two drive signals for  U501, U502, and they work in push 
pull topology driving, two transformers  are connected in parallel with each 
transformer driving two lamps in series. Turning each N-Channel MOSFET 
“on/off” complementarily, produces  an alternating current through the 
transformer primary and secondary. The “ on” duration of the switches determines 
the amount of energy delivered to  the CCFLs. R504, C504, R505, C505, R532, 
C529, R530, C522 are snubber networks, they  suppress Voltage transient spike in 
drain of power MOSFET. 
R506, R510, C509, C513, C514, R525, R531, C528, C525, and C527 are 
connected between high voltage output connector and ground, the divided AC 
voltage is inverted DC voltage th rough D502, D503, D508, and D509. The sense 
voltage feed back to VSEN (pin 6 of  IC501) for an over voltage/over current 
condition during normal operation. R528, R533,R523,R536 are current sense 
resistor, current sense signal feed back to  Isense (pin 5 of IC501) for lamp “ON” 
detection.  
 
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4.3    I/F Board Circuit  
4.2.1 Power  Input
 
- +5V is converted to 3V3(U101) and 1V8(U102) for U104. 
- +5V is fed to LVDS panel via Q101. 4.2.2  Scalar & MCU
 
- U104 (TSUM58WHJ) is a scalar IC with MCU. 
- U104 #77~#100 output 8 bit LVDS digital data to panel control circuit through 
CN104.  - U105 is a flash memory IC for program. 
- U107 and U202 is a EEPROM IC. 
4.2.2 VGA  Input
 
- The Red,Green,Blue input signals  come from CN103 #1,#2,#3 into TSUM58WHJ 
analog input terminals #28,#25,#23 via C112,C114,C116 and R115/117/119 are 
matching resistance which   
    pass through D102,D103 and D104 for over voltage protection. 
 
- Signal DDC_CLK (series clock) fro m CN103#15 passes through ZD101 for over 
voltage protection, and then goes  into EDID EEPROM IC U103 #6. 
- Signal DDC_DAT (series data) from  CN103#12 passes through ZD104 for over 
voltage protection, and then goes  into EDID EEPROM IC U104 #5. 
 
- Signal TTL vertical sync. (Vsync) fr om CN103 #14 passes through ZD102 (for over 
voltage protection),R131 and C123 and then goes into IC TSUM58WHJ#33. 
- Signal TTL horizontal sync. (Hsync)  from CN103 #13 passes through ZD103(for 
over voltage protection),FB101,R126,R 132,C122 and then goes into IC 
TSUM58WHJ#32. 
 
- CN103 #5 is defined as VGA cable dete ct pin, this detector realize via 
R129,R122,R123,R160 and U104 (TSUM58W HJ) #36, When cable plug in, 
DET_VGA is low level. 
 
-   U103 is an EEPROM IC,VGA EDID data is  saved in it and DVI EDID data in 
U201. 
4.2.3DVI Input (Option)
 
  - DVI RGB signal from CN201 #1,#2, #9,#10,#17,#18 goes into U104  #9,#10,#12,#13,#15,#16 via   
R201,R211~R215 respectively and then  are processed.D201,D203~D207 are ESD 
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protector to prevent U104 from ESD. 
 
- Digital clock DCLK+,DC LK- from CN201 #23,#24 pass es through D208,D209( for 
over voltage protection),R216,R217  and then goes into U104 #5,#6. 
 
 
 
4.2.4Button Control
 
Button “Key-Power” is defined as power on/of f, which is connected to U105 # 90 through 
CN105 # 6.  Button “Key-2” is defined as two functions  of selecting and adjustment, which is connected 
to U105 #94 through CN105 # 5.  Button “Key-Up” is defined as plus, which is connected to U105 # 95 through CN105 # 8. 
Button “Key-Down” is defined as minus, which is connected to U105 # 99 through CN105 # 
7.  Button “Key-1” is defined as two functions of  menu and exit, which is connected to U105 # 
89 through CN105 # 4. 
LED indicator on the front bezel is defined as follows: 
a. When press button “Key-Power”, U105 # 91 is  pulled down and U105 # 92 is pulled high, so 
Q102 is conducted and the LED indicator is green. 
b. When in power-saving mode, U105 # 91 is pulled high and U105 # 92 is pulled down, so  Q105 is conducted and the LED indicator is orange. 
 
4.4   FACTORY PRESET TIMING TABLE
 
 
TIMING FH(KHz) 
FV(Hz) 
Sync 
Polarity 
Total 
(Dot/Line)
Active 
(Dot/Line)
Sync Width 
(Dot/Line) 
Back Porch 
(Dot/Line) 
Pixel 
Freq.(MHz)
31.469 +  800  640  96  48 640*350@70Hz  70.086 −  449 350  2  60  25.175 
31.469 
−  800 640  96  48 640*400@60Hz 
59.940 −  525 400  2  73  25.175 
31.469 
−  800 640  96  48 IBM 
640*400@70Hz 
70.086 −  449 400  2  35  25.175 
31.469 
−  900 720  108 54 IBM 
720*400@70Hz 
70.087 +  449 400  2  35  28.322 
24.700 
−  800 640  96  48 640*480@50Hz 
50.000 −  494 480  2  8  19.760 
31.469 
−  800 640  96  40 VESA 
640*480@60Hz 
59.940 −  525 480  2  25  25.175 
640*480@67Hz 
35.000 −  864 640  64  96  30.240 
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 66.667 −  525 480  3  39   
37.861 
−  832 640  40  120 VESA 
640*480@72Hz 
72.809 −  520 480  3  20  31.500 
37.500 
−  840 640  64  120 VESA 
640*480@75Hz 
75.000 −  500 480  3  16  31.500 
35.156 + 
1024 800  72  128 VESA 
800*600@56Hz 
56.250 +  625 600  2  22  36.000 
37.879 + 
1056 800  128  88 VESA 
800*600@60Hz 
60.317 +  628 600  4  23  40.000 
48.077 + 
1040 800  120  64 VESA 
800*600@72Hz 
72.188 +  666 600  6  23  50.000 
46.875 + 
1056 800  80  160 VESA 
800*600@75Hz 
75.000 +  625 600  3  21  49.500 
31.250 
−  864 720  64  60 720*576@50Hz 
50.000 −  625 576  5  39  27.000 
49.725 
−  1152 832  64  224 MAC 
832*624@75Hz 
74.550 −  667 632  3  39  57.283 
39.634 
−
 
1312 1024  104  144 1024*768@50Hz 
49.980 + 
793 768  4  18  52.000 
48.363 
−
 
1344 1024  136  160 VESA 
1024*768@60Hz 
60.004 −
 
806 768  6  29  65.000 
56.476 
−
 
1328 1024 136  144 VESA 
1024*768@70Hz 
70.069 −
 
806 768 6  29  75.000 
60.023 +  1312 1024 96  176 VESA 
1024*768@75Hz 
75.029 +  800  768  3  28  78.750 
57.700 
− 1360 1024 136  144 1024*768@72Hz 
72.125 − 800  768  6  26  78.472 
67.500 
+ 
1600 1152 128  256 VESA 
1152*864@75Hz 
75.000 + 
900 864 3  32  108.000 
68.681 
−
 
1456 1152 128  144 MAC 
1152*870@75Hz 
75.062 −
 
915 870 3  39  100.000 
62.645  
 
1536 1152 120  192 1152*900@67Hz 
67.000  
935 900 3  31  96.223 
39.593  
−
 
1648 1280 128  184 1280*768@50Hz 
49.929 + 
793   768  7  15   60.500 
47.776 
−
 
1664 1280 128  192 1280*768@60Hz 
59.87 + 
798 768 7  20  79.500 
60.289  
−
 
1,696 1,280 128  208 VESA 
1280*768@75Hz  74.893 + 
805 768 7  27  102.250 
49.405  
−
 
1,680 1,280 128  200 1280*960@50Hz 
49.853 + 
991 960 4  24  83.000 
60.000 +  1800 1280 112  312 VESA 
1280*960@60Hz 
60.000 +  1000 960  3  36  108.000 
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75.231  − 1,728 1,280 136  224 1280*960@75Hz 
74.857 +  1,005 960  4  38  130.000 
49.405  
−  1,680   1,280   128   200  1280*1024@50Hz
49.853  +  1,057   1024  7   23   88.500  
63.981 +  1688 1280 112  248 VESA 
1280*1024@60Hz
60.020 +  1066 1024 3  38  108.000 
79.976 
+ 
1688 1280 144  248 VESA 
1280*1024@75Hz
75.025 + 
1066 1024 3  38  135.000 
47.712  
+ 
1,792   1,360   112  256  1360*768@60Hz 
60.015 + 
795   768  6   18   85.500 
54.113  
−
 
1,848   1,400   144   224  1400*1050@50Hz
49.965 + 
1,083   1050  4   26   100.000 
65.317 
−
 
1864 1400 144  232 1400*1050@60Hz
59.978 + 
1089 1050 4  32  121.750 
55.935  
−
 
1,904   1,440   152   232  1440*900@60Hz 
59.887 + 
934   900  6   25   106.500 
70.635  
−
 
1,936   1,440   152   248  1440*900@75Hz 
74.984 + 
942   900  6   33   136.750 
75.000  
+ 
2,160   1,600   192   304  VESA 
1600*1200@60Hz
60.000 + 
1,250   1200  3   46   162.000 
65.290  
−
 
2,240   1,680   176   280  1680*1050@60Hz
59.954 + 
1,089   1050  6   30   146.250 
 
4.5  Power On/Off Sequence
 
4.5.1 Hardware Power ON 
When power cord is plugged into AC socke t, SMPS starts work and provides U105 with 
VCC5V. When VCC5V inputs, U105 resets circuit active, sets U105 all registers to preset 
modes, and then monitor goes into stand-by mode. That means hardware power on has been 
completed.   
4.5.2 Software Power ON/OFF 
When press power key, U105 # 90 recieves lo w pulse,and then U105 will do the power on/off. 
-   If Power ON, U105 # 91(LED_Green) will send out Low potential, and then LED green on.     
-   If Power OFF, U105 # 91(LED_Green) will send out High potential, and then LED Off. 
The Panel_Vcc, Backlight_En, CLK/DATA output  to panel will follow the following sequency. 
 
 
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  T1 (ms)  T2 (ms)  T3 (ms)  T4 (ms) T5 (ms) T6 (ms)  T7 (ms) 
0.1~10 0~50  >200  >100  0~50  >0.1  >1000 
 
4.6 AC Outlet Pin Assignment 
                                  
Pin Symbol Description 
1 L  Live 
2 N  Neutral 
3 E  GND 
 
 
4.7  Inner Connector Pin Assignment 
4.7.1 CN501, CN502, CN503, CN504 (
Connect to Panel Backlight, 
SM02B-BHSS-1-TB or equivalent
) 
Pin Symbol Description 
1  H.V.  High voltage for lamp 
2  L.V.  Low voltage for lamp 
   
 
 
 
 
 
 
P801
12
3
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4.7.2CN101 (Power BD to Interface BD) 
Pin No. Symbol Description 
1 VCC5V +5.1V INPUT 
2 VCC5V +5.1V INPUT 
3 GND GND 
4  ON/OFF  CCFL on/off control 
5  BRIGHTNESS  Panel luminance control (CCFL brightness) 
6 GND Ground 
7  VOL  Volume control input   
8  MUTE  Mute control input   
 
 
 
4.7.3CN105 (Interface BD to Keypad) 
Pin 
No. Symbol Description 
1  LED_ GREEN    Orange LED lighting control 
2  LED_ ORANGE  Green LED lighting control 
3 GND  Ground 
4  KEY_POWER    DC power on/off control, 
5 KEY_UP&
▲ 
OSD “▲” control to adjust value to increase, 
6 KEY_DOWN&2  Select control  and auto adjustment control, 
7 GND  OSD “▼” control to adjust value to decrease 
8  KEY_1  OSD menu and exit 
 
 
 
 
 
 
 
 
 
 
 
 
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4.7.4CN104 (Connect I/F BD to panel, FI-X30S-H or Equivalent) 
Pin No. Symbol Function 
1  RXO0-  minus signal of odd channel 0(LVDS) 
2  RXO0+  plus signal of odd channel 0(LVDS) 
3  RXO1-  minus signal of odd channel 1(LVDS) 
4  RXO1+  plus signal of odd channel 1(LVDS) 
5  RXO2-  minus signal of odd channel 2(LVDS) 
6  RXO2+  plus signal of odd channel 2(LVDS) 
7 GND  Ground 
8  RXOC-  minus signal of odd clock channel (LVDS) 
9  RXOC+  plus signal of odd clock channel (LVDS) 
10  RXO3-  minus signal of odd channel 3(LVDS) 
11  RXO3+  plus signal of odd channel 3(LVDS) 
12  RXE0-  minus signal of even channel 0(LVDS) 
13  RXE0+  plus signal of    even channel 0(LVDS) 
14 GND  Ground 
15  RXE1-  minus signal of even channel 1(LVDS) 
16  RXE1+  plus signal of even channel 1(LVDS) 
17 GND  Ground 
18  RXE2-  minus signal of even channel 2(LVDS) 
19  RXE2+  plus signal of even channel 2(LVDS) 
20  RXEC-  minus signal of even clock channel (LVDS) 
21  RXEC+  plus signal of even clock channel (LVDS) 
22  RXE3-  minus signal of even channel 3(LVDS) 
23  RXE3+  plus signal of even channel 3(LVDS) 
24 GND  Ground 
25 GND Ground 
26 GND  Ground or Open 
27 GND Ground 
28  VCC  Power supply (5.0 V) 
29  VCC  Power supply (5.0 V) 
30  VCC  Power supply (5.0 V) 
 
 
 
 
 
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