According to the failure analysis of a machine is a element thermal stability; 2 it is to switch power or line scan normal work needed for the start signal to form circuit has a problem. In case of can't boot failure, if measured + lllV output voltage of 0 v, the fault in the switching power supply. While the start of switch power supply, signal, there are two: one is the output rectifier filter circuit with 300 v dc voltage ripple; 2 it is switch tube Q810 on moment needs a trigger voltage. In can't boot state measurement Q810 collector voltage of 285 v, normal; Test the Q810 the base voltage have voltage, but in the press the power switch again jump is small when the phone is switched on. Judge fault in start-up circuit. Check the R803 normal start-up circuit. Check D806 associated with starting circuit, Q802, C810 element, found for Q802 thermal stability is poor, and the c and e electrode resistance with the temperature rising and falling, the Q801 base current shunt effect, lead to not boot. Replace Q802 after commissioning, troubleshooting.xkTservice manual download site