Check insurance tube F1 is normal, and electric measurement on both ends of the capacitor C2, C4 voltage 300 V normal, measuring the IC3 (1), 6 foot voltage 300 V normal, measure the voltage of 4.6 V 5 feet or so, check D7, R16, C15 all normal. TAXservice manual download site
 TAXservice manual download site
After inspection found that the secondary load capacitance C7 breakdown short circuit. The feedback winding output of high-frequency pulse voltage via R16, D7 rectifier. On both ends of C15 capacitance voltage down to 4.6 V, the IC3 within 5 feet of low voltage protection circuit action, make the switch tube to stop working, and to prevent due to insufficient supply, leading to damage due to lack of excitation voltage switch tube. Replace the capacitor C7, troubleshooting.TAXservice manual download site