Thursday, January 24, 2013

AOC F22S _ LCD MONITOR _ TROUBLESHOOTING



NO SCREEN APPEAR [MAIN BOARD]


No power









Press power key and look if the picture is normal.





NG





Please reinsert and make sure the AC of 100-240 is   normal


NG
Reinsert or check the power section


OK





Measure U404 Vout=3.3V Q409 VC=1.8V
NG
Measure CN404 PIN5/6=3.3V?
Measure CN404 PIN3/9=5V?



OK

OK
NG
Check power
section
X401 oscillate waveforms are normal


Replace U404, Q409


OK
NG
Replace X401



Replace U401





NO PICTURE.  LED ORANGE


No picture





Measure U404 Vout=3.3V
Q409 Vc=1.8V

Ng
Replace U404, Q409
Ok



X401 oscillate waveforms are
Normal.



Ok
Ng
Replace X401

Check if the sync signal from computer is output and video cable is connected
normally.



Ok
Ng
Input the sync signal of
computer, or change the
cable
Replace U401



NO POWER.  POWER BOARD


Check CN902 pin3= 12V



Ng



Check AC line volt 110V or 220V

Ng
Check AC input
Ok



Check the voltage of C905A (+)

Ng
Check bridge rectified circuit and F901 circuit
Ok



Check start voltage for the pin3 of U901



Ok
Ng
Check R912,R904 and Change U901
Check the auxiliary voltage is bigger than 10V and smaller than 20V



Ok
Ng
Check U901
Check U901 pin8 PWM wave



Ok



Check Q901,R910,T901,D900,D901



W/LED.  NO BACK LIGHT


Check C802 (+) =12V



Ok
Ng
Change Q802

Check ON/OFF signal



Ok

Ng
Check main board
Check U801 pin6=12V



Ok

Ng
Change Q804 or Q809
Check the pin1 of U801 have saw tooth wave. 
Change U801

Check T801/T802 have the output of square wave at short time



Ok
Ng
Check C801/C825/D815/D814
Check C812/C826/D817/D816
Check the output of T801/T802



Ok

Ng
Change T801/T802
Check connecter & lamp