Acer AL1721h Service Manual page 36

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2.Panel-Power Circuit
Check R302 should have response
from 0V to 5V
When we switch the power switch
from on to off
OK,R308 have response
Measured the Q302 pin 5,6,7,8= 5 V?
OK
OK
3.Inverter Control Relative Circuit
Measured the inveter connector CN402
Pin2 on/off control=3.3V (on)
Pin4 PWM signal control dim 0V-5V
Replace Power board to new-one, and
Check the screen is normal ??
OK
NG
NG, no Voltage
NG, still no screen
Check the PPWR panel power relative circuit,
Q301, Q302(pin 5,6,7,8)
In normal operation, when LED =green, R302
should =0 v,
If PPWR no-response when the power switch
Turn on and turn off, replace the U203-GM5120/2120
Check U202 pin 1,2,3,4= 5V
Replace Q302 ( Nmos, SI9933)
Check the Bklt-On relative circuit, R409,
In normal operation, when LED =green,
NG
R409 Bklt-On should =5 v,
If Bklt-On no-response when the power
switch turn on-off,
Replace U203 GM5120
NG
35
Yes
Replace Power board
& Re-do white balance

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