Acer AL2016 Service Manual page 7

Acer
D804 R813 R814 and C806, This will prevent MOSFET from being damaged under large current
impulse and voltage spike.
2.1.3 DC_18V, DC 5V and DC_3.3V Output Circuit
For DC 18V, D807 is used to rectify the inducted current. R816 and C814 are used to store energy
when current is reversed. The parts including C815,C816,C817 and L802 are used to smooth the
Voltage waves.
For DC 5V, a PWM DC to DC circuit is used to get DC 5V from DC 18V. IC804 is the PWM controller.
C826 decide PWM operation frequency. Q802, D808 and D810 made up of buck circuit to get DC 5V.
C825, B801, C824 and C820 are used to smooth the Voltage waves.
For DC 3.3V, a PWM DC to DC circuit is used to get DC 3.3V from DC 18V. IC805 is the PWM
controller. C829 decide PWM operation frequency. Q806, D811 and D812 made up of buck circuit to
get DC 3.3V. C832, B802, C830 and C833 are used to smooth the Voltage waves.
2.1.4 Feedback and OVP Protect Circuit
Pin R of IC803 is supplied 2.5V stable voltage. It is connected to 18V through R823, R837 and R822.
R823 R837 and R822 are output sampling resistor. When the sampling voltage more than 2.5V or less
than 2.5V, feedback current control IC802 to change pulse width. That can stabilize the out put voltage
through transformer T801.
Q803, R828, C834, R827, ZD803, ZD804 and ZD806 made up of over voltage protection circuit.
When DC out put 18V over 20V, the ZD803 zener will breakdown. If DC out put 5V over 5.6V, the
ZD804 will breakdown. If DC out put 3.3V over 3.9V, the ZD805 will breakdown. Any zener of
ZD803, ZD804 and ZD805 breakdown, the Q803 be triggered. Then the PWM controller (IC802) stop
output switch waveform. But the IC802 is a recovery controller. When remove the issue, DC out put
will automatically recover.
2.2 I/F Board Circuit
2.2.1 RGB CAPTURE
- Signal RED,GREEN,BLUE input through CN102 #1,#2,#3, Stop DC via C117, C118 and C119,
and then enter into U105 (MST9251A) analog input terminal #33,#30,#28, and then MST9251A
deals with signal internally. D103,D104,D105 are ESD protector to prevent U105 from ESD.
- Signal DDC_SCL (series clock) inputs via CN102#15, and then passes through ZD105 Zener for
ESD protection, goes into EDID EEPROM IC U103 #6.
- Signal DDC_SDA (series data) inputs via CN102#12, and then passes through ZD104 Zener for
ESD protection, goes into EDID EEPROM IC U103 #5.
- Signal TTL vertical sync. (Vsync) inputs via CN102 #14, and then clamped by ZD103 Zener,
passes through R122, and then goes into IC U105 (MST9251A) #37.
- Signal TTL horizontal sync. (Hsync) inputs via CN102 #13, and then clamped byZD101 Zener,
passes through FB103,R123, and then goes into IC U103 (MST9251) #36.
- CN102#5 is defined as cable detect pin, and then passes through ZD104 Zener and R137 for ESD
Protection. This detector realized passes through R145 Pull hight, go into U107 #31.
- U103 +5V is supplied by PC via CN102#9, or supplied by Monitor self via D102.
- U103 is an EEPROM IC which is memory and EDID data saved in it.
2.2.2 Buttons Control
- Button "Power" on right side bezel connects to U107 (MTV312) #41 through R155, via
CN103#4.
- Button "AUTO" "LEFT" "RIGHT""MENU" on right side bezel connects to U107 (MTV312)
#3,#2,#1,#42 through R149,R150,R153,R154,via CN103 #8, #7, #6, #5.
- U104 is an EEPROM IC which memory factory setting and save the value adjusted by user.
- SCL on U104 #6 and SDA on U106 #5 flow into U107 (MTV312) #13, #14.
- LED Indicator on Front Bezel
a. When press button "power", U107 (MTV312) #26 sends out low potential, via R151,then
launch Q105, flow to CN103 #3 on keypad, LED Green ON.
b. When in "Suspend" mode, U107 (MTV312) #27 sends out a low potential, via R152, then
launch Q106, flows to CN103 #2 on keypad, LED Amber ON.
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Service Manual