Dell E190Sf - Page 11

Service Manual
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D854 is used to rectify the inducted current. R862 and C861 are used to store energy when current is
reversed. The parts including C862, C865 and L852 are used to smooth the current waves that are from
D855, then 13V voltage is supplied.
D856 and D857 are SCHTKY diodes used to rectify the inducted current.C866 and R866 are used to
store energy when current is reversed,The components including C864,C874,C875,L851 and C876 are
used to smooth the current waves,then DC+5V voltage is supplied. F851 is used for OCP for the LPS test.
DC 5V supply voltage feed back to PWM controller U850 via R861,R860,R859,C859,I851,R857,
R863 used to control the voltage feedback loop.
2.3 I/F Board Circuit
2.3.1 RGB CAPTURE
- Signal RED,GREEN,BLUE input through CN301 #1,#2,#3, Stop DC via C303, C302 and C301, and
then enter into U401 (gm2621-LF) analog input terminal #99,#96,#93, and then gm2621-LF deals
with signal internally. D303, D302, D301 are ESD protector to prevent U401 from ESD.
- Signal DDC_SCL (series clock) inputs via CN301#15, and then passes through ZD305 for ESD
protection, goes into EDID EEPROM IC U301 #6.
- Signal DDC_SDA (series data) inputs via CN301#12, and then passes through ZD306 for ESD
protection, goes into EDID EEPROM IC U301 #5.
- Signal TTL vertical sync. (Vsync) inputs via CN301 #14, and then clamped by ZD302 Zener, passes
through R311, and then goes into IC U401 (gm2621-LF) #90.
- Signal TTL horizontal sync. (Hsync) inputs via CN301 #13, and then clamped by ZD303 Zener,
passes through R310, and then goes into IC U401 (gm2621-LF) #89.
- CN301#5 is defined as cable detect pin, this detector realize via R319 and U401#114, and ZD301 is
ESD protector.
- U301 +3.3V is supplied by PC via CN301#9 or supplied by Monitor self via D307 with D306 and
ZD304 for ESD protection,.
- U301 is an EEPROM IC which is memory and EDID data saved in it.
2.3.2 Buttons Control
- Button “Power” on front bezel connects to U401 (gm2621-LF) #125 through CN401 #8, U401 #125
is defined as power on/off.
- Button “+” on front bezel connects to U401 (gm2621-LF) #124 through CN401 #3, U401 #124 is
defined as “Plus”.
- Button “-” on front bezel connects to U401 (gm2621-LF) #123 through CN401 #2, U401 #123 is
defined as “Minus”.
- Button “Menu” on front bezel connects to U401 (gm2621-LF) #122 through CN401 #1, U401 #122 is
defined as “Menu”.
- LED Indicator on Front Bezel
a. When press button “power”, U401(Scalar) #125 be send in low potential, make U401#57 sends out
high potential, and then to J1#2 on keypad, LED Green on.
b. When in “Suspend” mode, U401 (Scalar) #56 sends out a high potential, and then to J1 #3 on
keypad, LED Amber ON.
2.3.3 ST CHIP U401 (gm2621-LF)
- U401 (gm2621-LF) #7~#10 output 8 bit even and #31~#40 output 8 bit odd LVDS digital data to
panel control circuit through CN501.
- U401 (gm2621-LF) #127 output PPWR ”H” potential to make Q502 conducted, and then make Q501
conducted, +5V flow to CN501#1~#3 as Panel Vdd .
- U401 (gm2621-LF) #49 output CCFL_ON/OFF ”H” potential to control Inverter on/off.
- U401 (gm2621-LF) #50 outputs Brightness “PWM” signals to control CCFL brightness.
- TCLK by Crystal 14.318MHz input to U401 (gm2621-LF) #109.
- U401 (gm2621-LF) #111 Bidirectional RESET signals
Please refer to gm2621-LF Pin Assignments table in page
2.3.4 Regulator Circuit