Buffalo FTD-G731AS Service Manual page 20

No Backlight
Check C223 (+) =12V
Check ON/OFF signal
OK
Check U201 pin9=12V voltage
OK
Check the pin10/Pin7 of U201 have saw tooth
NG
Short Q203/Q204 if the picture normal
NG
Connect PIN15 of U201 to the ground and check
Q209/Q210/Q211/Q212 collector waveforms
OK
Check feedback circuit
NG
OK
NG
NG
OK
NG
Check F902
Check D201/Q209/Q210
Check D202/Q211/Q212
Check Interface board
Change Q201 or Q207
Replace U201
1) Replace Q209/Q210/PT201
2) Replace Q211/Q212/PT202
NG
Check connecter & lamp
20
BUFFALO Service Manual