The output of the switch power supply is only about 40V, and the positive and negative values of the Q501Ve electrode are 2K, 2.5k, and the suspected line is a problem, and the measurement is normal.. To detect inverse range capacitance, in road test c510 at both ends of the resistance value is very small, remove c510 measurements in normal and analysis may be Cor. breakdown (see the figure).
Replace D503, turn on and burn.. The reason of the D503 breakdown is that the C509 (1500pF) and C510 (0.056 u F) are not normal.. According to the capacity of C510, C509, the reverse voltage of D503 is no more than 3.0V (static), D503 again breakdown, the underlying cause is C509 problem. Remove C509 to measure its leakage resistance of about 2K, after replacing C509, D503, the machine works normal.