Service manual

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2.3 I/F Board Circuit
2.3.1 Power Input
+3.3V is from the power board and supply for U101(LD1117AL-1.8V)﹑U102(AT24C02N) ﹑U103(TSUM16AL) ﹑
U104(SST25VF010A) ﹑U105(AT24C04N) ﹑panel and LED. +1.8V output is generated from +3.3V through C104
and C105 filtering, and U101 outputs. +1.8V is only used for U105.
2.3.2 MCU & Scaler(TSUM16AL)
The frequency of XTAL1 is 14.318MHz. U103 # 48 is defined as panel-enable. When the I/O port is low, Q106 and
Q105 are conducted. And then after C116 and C117 filtering, obtain the voltage of VLCD, which will be connected
to CN104. U103 # 85 is defined as CCFL-enable. When the I/O port is low, Q102 is pulled up and the backlights
are on; When the I/O port is high, Q106 is conducted and the backlights are off. U103 # 35 is defined as DET-VGA,
connected with CN103 # 5. U103 # 84 is a pin of hardwire reset. U103 # 54-# 55,# 58-# 65 output LVDS digital
data of 8 bit to panel control circuit through CN104. U103 # 86 generates a PWM waveform by regulating the duty
to control the brightness of the backlights.
U102 is EEPROM used for saving EDID data, which is connected by SCL and SDA pins with # 31 and # 30 of
TSUM16AL.
U104 is a flash memory, U104 # 2, # 1, # 6, # 5 are the communications with U103 # 37-# 40.
U105 is EEPROM used for saving user’s OSD setting. U105 is connected by SCL and SDA pin with # 44 and # 43
of TSUM16AL.
2.3.3 VGA Input
Signal R, G, B input through CN103 # 1, # 2, # 3, and C116, C117 and C118 filtering the high frequency noise.
Signal HSYNC and VSYNC input through CN103 #13 and #14, and C126, R131, C125, R130 filtering. Then the
analog signal enters U103, and then U103 deals with it internally. In addition, D101, D102, D103, D104 (the four
are BAV99), ZD101, ZD102, ZD103, ZD104, ZD105 (they are constant voltage diode of 5V6) are ESD protector.
Signal DDC-SCL inputs via CN103 # 15, and then passes through ZD101 for ESD protection, goes into EDID
EEPROM IC U102. Signal DDC-SDA inputs via CN103 #12, and then passes through ZD105 for ESD protection,
goes into EDID EEPROM IC U102. CN103 # 5 is defined as cable detect pin, this detector realizes via R126 and
U103 # 35,The PC-5V of U102 is supplied by PC via CN103 # 9 with ZD102 for ESD protection, or supplied by
Monitor self via D105.U105 is an EEPROM IC, which is a kind of memory and used for saving EDID data.
2.3.4 Button Control
Button “Key-Power” is defined as power on/off, which is connected to U103 # 90 through CN101 # 6.
Button “Key-2” is defined as two functions of selecting and adjustment, which is connected to U103 # 94 through
CN101 # 5.
Button “Key-Up” is defined as plus, which is connected to U103 # 95 through CN101 # 8.
Button “Key-Down” is defined as minus, which is connected to U103 # 99 through CN101 # 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”, U103 # 91 is pulled low and U103 # 92 is pulled high, so Q103 is conducted
and the LED indicator is green.
b. When in power-saving mode, U103 # 91 is pulled high and U103 # 92 is pulled low, so Q104 is conducted and
the LED indicator is orange.