Overhaul with emphasis on the power input and transform parts of the fault. C12 310V-free DC voltage measurement first, and if there is, most for V3 and V4 transform part does not start. If using digital multimeters to measure between V3 and V4 base to emitter voltages of around -0.3V or did not start. In this case, check the T1, N1, N2 and biasing circuit component failure of deficiency-free soldering, unsoldering, etc; if it is starting, then N3 for T1, T2, N1, C9 circuit open circuit.