Buffalo BU1715 Service Manual page 39

2. Panel Power Circuit
Check R207 should have response from 0V to 5V
When we switch the power switch from off to on
Check Q204, Q203 is broken or CN503 solder abnormal?
OK
Replace Panel
3. Inverter Control Relative Circuit
Measured the inverter connector CN102
Pin 1 on/off control=5V (on)
Pin 2 PWM signal control dim 0V-5V
Replace Power board
& Re-do white balance
OK
NG
Replace Q204, Q203 or re-solder CN503
OK
NG
Measured X601 waveform is normal?
Replace U601
Check the Bklt-On relative circuit, R201, Q201,
NG
In normal operation, when LED =green,
Base of Q201 should =0 V,
In saving mode, when LED=orange,
Base of Q201 should =5 V,
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Buffalo BU1715
NG
Replace X601
OK
OK
Replace U601