17" LCD Color Monitor HP L1740
31
2. W/LED No Backlight
Check C820 (+)/C840 (+) =12V
NG
OK
Check C820/C840
Check ON/OFF signal
Check Interface board
NG
OK
Check U811 pin1=5V ?
NG
OK
Change Q821 or Q841
Check the pin1 of U811 have saw tooth wave
NG
OK
Change U811
Check D833、D853 has the output of square wave at short time.
NG
OK
CheckQ821/Q841
Check the resonant wave of pin2 & pin5 for PT801/PT802
NG
Check the output of PT801/PT802
Check Q821/Q841/D833/D853
Check connecter & lamp
OK
NG
Change PT801/PT802
OK
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