Service manual
ViewSonic Corporation Confidential - Do Not Copy VA702-1_VA702b-1
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3.4 VGA 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.
3.5 Button 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 through
CN106 #2.
LED indicator on the front bezel is defined as follows:
a. When press button “Key-Power”, U105 #6 is pulled down and U105 #7 is pulled high, so Q104 is
conducted and the LED indicator is green.
b. When in power-saving mode, U105 #6 is pulled high and U105 #7 is pulled down, so Q105 is
conducted and the LED indicator is orange.
3. FACTORY PRESET TIMING TABLE
Item Resolution
H-Freq.
(KHz)
V-Freq.
(Hz)
Dot Clock
(MHz)
1 640 x 350 31.5kHz 70Hz 25.2
2 640 x 400 31.5kHz 60Hz 25.2
3 640 x 400 31.5kHz 70Hz 25.2
4 24.7kHz 50Hz 19.8
5 31.5kHz 60Hz 25.2
6 35.0kHz 67Hz 30.2
7 37.9kHz 72Hz, 31.5
8 37.5kHz 75Hz, 31.5
9
640 x 480
43.27kHz 85Hz 36.0
10 720 x 400 31.5kHz 70Hz 28.3
11 35.1kHz 56Hz 36.0
12 37.9kHz 60Hz 40.0
13 48.1kHz 72Hz 50.0
14 46.9kHz 75Hz 49.5
15
800 x 600
53.7kHz 85Hz 56.3
16 832 x 624 49.7kHz 75Hz 57.3
17 48.4kHz 60Hz 65.0
18 56.5kHz 70Hz 75.0
19 58.1kHz 72Hz 78.5
20 60.0kHz 75Hz 78.8
21
1024 x 768
68.67kHz 85Hz 94.5
22 1152 x 870 68.6kHz 75Hz 100
23 63.4kHz 60Hz 108
24
1280 x 1024
79.97kHz 75Hz 135
25 1280 x 720 45kHz 60Hz 74.2