Good check rectifier filter components D801 and C822 (switching power supply), D6712, C883 (Deputy switching mode power supply), and check of main and auxiliary switch power supply module IC801 and IC881, found IC801 (STR6656LF53) (2) - (3) feet in MOSFET switch tube breakdown.

Local circuit of the main power supply of the machine is shown in fig.. IC801 switch tube damage to the main reason is: switch transformer T801 (4) (8) local main winding short circuit; IC801 (1) foot pulse width modulation voltage stabilizing circuit out of control; IC801 (1) foot switch tube delay conduction circuit anomalies. The resistance of R836 open circuit, for troubleshooting.

Voltage comparator and D820, R837,, C829, R836,, IC801,,, D821. T801 (2) - (1) winding induction pulse voltage via d821 rectifier and R836 limit flow to C829 charging charging voltage (1) foot isolation diode D820 added to IC801, its voltage in the T801 energy release after not immediately dropped to below 0.73v, MOSFET switch tube has been in cut-off state. During this period, C829 by r837 discharge. Only when the IC801 (1) pin voltage dropped to -0.73 V, the switch to guide (1 / 2 cycle after the start of the resonance, i.e. the resonant curve Valley), to MOSFET conduction losses reduced to a minimum. If the delay of the conduction function is invalid, the loss of the conduction loss of the switch tube in IC801 is increased, and the temperature is increased.