ViewSonic VA702B Service Manual - Page 23

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 1 640 x 350 2 640 x 400 3 640 x 400 4 5 6 7 640 x 480 8 9 10 720 x 400 11 12 13 800 x 600 14 15 16 832 x 624 17 18 19 1024 x 768 20 21 22 1152 x 870 23 1280 x 1024 24 25 1280 x 720 ViewSonic Corporation H-Freq. (KHz) 31.5kHz 31.5kHz 31.5kHz 24.7kHz 31.5kHz 35.0kHz 37.9kHz 37.5kHz 43.27kHz 31.5kHz 35.1kHz 37.9kHz 48.1kHz 46.9kHz 53.7kHz 49.7kHz 48.4kHz 56.5kHz 58.1kHz 60.0kHz 68.67kHz 68.6kHz 63.4kHz 79.97kHz 45kHz V-Freq. (Hz) 70Hz 60Hz 70Hz 50Hz 60Hz 67Hz 72Hz, 75Hz, 85Hz 70Hz 56Hz 60Hz 72Hz 75Hz 85Hz 75Hz 60Hz 70Hz 72Hz 75Hz 85Hz 75Hz 60Hz 75Hz 60Hz Confidential - Do Not Copy 20 Dot Clock (MHz) 25.2 25.2 25.2 19.8 25.2 30.2 31.5 31.5 36.0 28.3 36.0 40.0 50.0 49.5 56.3 57.3 65.0 75.0 78.5 78.8 94.5 100 108 135 74.2 VA702-1_VA702b-1