Acer AL1921 - Page 47

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2.Panel-Power Circuit
3.Inverter Control Relative Circuit
Yes
Check R302 should have response
from 0V to 5V
When we switch the power switch
from on to off
NG
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-MST8131B
OK,R308 have response
NG, no Voltage
Measured the Q302 pin 5,6,7,8= 5 V?
Check U202 pin 1,2,3,4= 5V
OK
OK
Replace Q302 ( Nmos, SI9933)
NG
Check the Bklt-On relative circuit, R409,
In normal operation, when LED =green,
R409 Bklt-On should =5 v,
If Bklt-On no-response when the power
switch turn on-off,
Re
p
lace U203 MST8131B
NG, still no screen
Replace Power board to new-one, and
Check the screen is normal ??
OK
NG
Replace Power board
& Re-do white balance
Measured the inveter connector CN402
Pin2 on/off control=3.3V (on)
Pin4 PWM signal control dim 0V-5V