Buffalo BU1715 Service Manual page 41

8.2.3 Power/Inverter Board
1.) No power
Check to CN102 pin12 = 12V
OK
Check the voltage of C905(+)
OK
Check start voltage for the pin3 of IC901
OK
Check the auxiliary voltage is smaller than 20V
OK
Check D910, D912, IC902, IC903
NG
Check Interface board
Check AC line volt 120V or 220V
NG
Change F901; check BD901, Q903, and IC901
NG
Check R906, R907, IC901
NG
1) Check IC902, IC903, ZD901
2) Check Q901, Q902...OVP circuit
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Buffalo BU1715