ViewSonic VS13518-1W, Service Manual

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80,#81-#82, #83-#84, #85-#86,#87-#88 output LVDS digital data of 8 bit to panel control
circuit through CN105. U105 # 117 generates a PWM waveform by regulating the duty to
control the brightness of the backlights.U103 is EEPROM used for saving EDID data,
which is connected by SCL and SDA pins with #35 and #34 of NT68668FG. U108 is a
flash memory, U106 # 6, # 5 are the communications with U105 #49-#50.U106 is
EEPROM used for saving user’s OSD setting.
4.3.3 VGA Input
Signal R, G, B input through CN102 #1, #2, #3, and C116, C117 and C118 filtering the
high frequency noise. Signal HSYNC and VSYNC input through CN102 #13 and #14, and
C129, R135, C130, R136 filtering. Then the analog signal enters U105, and then U108
deals with it internally. In addition, EP112, EP107, EP104, EP105, EP106, EP108, EP109,
EP110, EP111,are ESD protector. Signal DDC-SCL inputs via CN102 #15, and then
passes through EP108 for ESD protection, goes into EDID EEPROM IC U103. Signal
DDC-SDA inputs via CN102 #12, and then passes through EP111 for ESD protection,
goes into EDID EEPROM IC U103. CN102 #5 is defined as cable detect pin, this detector
realizes via R121 and U105 #29,The PC-5V of U103 is supplied by PC via CN102 #9 with
EP107 for ESD protection, or supplied by Monitor self via D106. U103 is an EEPROM IC,
which is a kind of memory and used for saving EDID data.
4.3.4 Button Control
Button “Key-Power” is defined as power on/off, which is connected to U105 #122 through
CN104 #6. Button “Key-2” is defined as two functions of selecting and adjustment, which is
connected to U105 #125 through CN104 #2.
Button “Key-Up” is defined as plus, which is connected to U105 # 67 through CN104 #10.
Button “Key-Down” is defined as minus, which is through connected to U105 #126 through
CN104 # 5.
Button “Key-1” is defined as two functions of menu and exit, which is connected to U105 #
66 through CN104 # 1.
LED indicator on the front bezel is defined as follows:
a. When press button “Key-Power”, U105 # 124 is pulled high and U105 # 123 is pulled
Low, so Q108 is conductedand the LED indicator is Blue.
b. When in power-saving mode, U105 # 123 is pulled high and U105 #124 is pulled down,
so Q106 is conducted andthe LED indicator is orange.
4.4 Power On/Off Sequence
4.4.1 Hardware Power ON
When power cord is plugged into AC socket, SMPS starts work and provides U105 with
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