Dell E153FPTc Service Manual page 43

No Backlight
Check D201 (-) have the output of square wave at short time.
Check the resonant wave of pin2 & pin5 for PT201
Check C201 (+) =12V
OK
Check ON/OFF signal
OK
Check U201 pin9=12V
OK
Check the pin1 of U201 have saw tooth wave
OK
OK
OK
Check the output of PT201
OK
Check connecter & lamp
NG
Change F902
NG
Check Interface board
NG
Change Q201 or Q202
NG
Change U201
NG
CheckQ205/Q204/Q203
NG
Check Q206/Q207/C210
NG
Change PT201
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DELL E153FPTc