Dell S1909WXf Service Manual page 31

Power (include IF +5Vand +3.3V) supply normal but LED off and no display
Is the key function OK?
Is the frequency 14.318MHz at #32 of
Is the low active reset signal at #19 of
IF Board U104 normal?
Is the serial clock signal at #6 of IF
Board U105 normal when power AC on?
Upgrade Firmware to Serial Flash U105
by VGA port with ISP_Tool V4.100.exe
Power (include IF +5Vand +3.3V) supply and display normal only LED off
Is the keypad cable connective OK
Is LED at keypad work OK
Is theLED control signal at 31# of U104
high-low convertible when DC on/off
NO
IF Board U104?
Yes
Yes
Yes
END
Yes
Yes
Is R188 open?
NO
Is Q109 work normal?
Yes
END
Yes
Press power key to DC on the monitor,if
display ok the process is end,if no display see
the no backlight process
NO
NO
Yes
NO
NO
Reassembly or changing
NO
Change LED
Yes
Change R188
NO
Change Q109
NO
Change U104
30
Service Manual
Change crystal X101
Change C160
NO
Change U104
Change U105