Analysis the cause of the failure, it may be the power supply or the horizontal output stage with the components inside poor, oscillation or line-level performance is poor. According to the principles of maintenance of the easy issues before the tough ones, "Squeak" sound after the percussion circuit board, discovered Squeak varies widely, initially thought to be caused by the poor contact of the component failure. The author to inspect the power supply and the output stage of the suspicious elements, when the check to L305, Squeak varies greatly suspected L305 inner core is loose. Trial within a small knife into the modified L305 cores, Squeak was eliminated. After wax drip L305 cores, boot failure does not occur again for a long time, indicating fault has been ruled out.