Observe the machine after startup, relay suck up vocalist, directives microprocessor has a boot, and the grid to the main power supply circuit, according to the light is not to green, to judge the fault in the main or protection switch power supply circuit, the measuring point voltage, judge the fault range, measuring large filter capacitance C818 anode voltage 300 v, boot moment about the suyddenly rising voltage of 320 v, and then relay RL801 disconnect to Ov, the judgment is mains rectifier switch circuit fault, under the condition of 220 v mains, go doubler rectifier state, cause overvoltage protection circuit starts. Boot, the positive voltage measurement D819 light-emitting diodes (oleds), there are about 1 v suyddenly rising voltage, further judgment is mains rectifier circuit malfunction. For grid rectifier circuit inspection, found that The Times pressure, full-wave rectifier switch circuit IC895 (STR83145LF55) internal short circuit. Demolition of the circuit, instead of full wave rectifier, troubleshooting.QpXservice manual download site