Power Include If +5V And +3.3V) Supply Normal Key Function Ok, But Backlight Can Tbe Turned On - Dell ST2010 Service Manual

Service Manual
6. Power (include IF +5Vand +3.3V) supply normal ,key
function OK,but backlight can't be turned on
Backlight cannot be turned on,is the
on-off control signal come from IF ok?
Yes Is the on-off control signal #109 of U105
Yes
high-low convertible when DC on/off
Is the
NO Check
voltage
T850 or
13Vat T1
F850
PIN3/4
Yes
Check U1
pin2 Voltage
is 5V
Yes
Check U1 NO Check
pin6Voltage is CN851
High
YES
Check U1 pin1 and pin2 Oupput
NO
Yes
Change Q1
43
NO
Is the CN851
inserted CN101 OK?
Yes
NO
Change U105
Check
U1