After startup can hear the power on and off control relay and action, comprehensive protection circuit can be preliminary control of factors; Estimation problem is some reason causing oscillation circuit switch power supply caused by vibration. Open the machine cover, switched on testing plug-ins D7 (1), (2) feet between dc voltage is 290 v, normal, rectifying mode switch control circuit element is good; Test again thick film blocks IC801 (5) feet start voltage of 13.2 V, shows good start oscillation circuit, to detect IC801 (4) feet voltage of 2.6 V, normal should be 1.2 V, obviously higher than normal, that accused IC801 internal over-current protection circuit. IC801 caused by circuit analysis, (4) feet high voltage factors are: IC801 diamond effect switch tube leakage current is too large; IC801 (2) the foot of the external flow detection is proposed.theoretical larger; Switch transformer T801 secondary rectification filter circuit exists leakage or its load short circuit; Doubler rectifier output overvoltage protection circuit to poor monitoring element of misoperation Q803 saturated conductivity or Q803 beam junction leakage damage etc. Try to narrow the fault range, desoldering D822 pins, disconnect Q803 on voltage control function, (4) feet again short boot detection + B output voltage has returned to normal. The machine has been observed at this time, all the control function back to normal, fault is judged by R816, t {817, D820, Q803 bad cause overvoltage protection monitoring circuit, composed of misoperation caused by. Q803 was detected in b, c, e voltage of 4.1 V, 13.1 V, 3.6 V, obviously the tube b and c voltage is not normal (normal, in turn, 0.3 V, 0.2 V), so they are in conduction Q803; To detect 1:18 18 on both ends of the voltage of 9.4 v is normal, so the judge lOV stabilivolt D820 leakage damage.xzLservice manual download site