This machine adopt series switch regulated power supply, to prevent load over-voltage damage caused by the failures of power supply, the overvoltage protection measures. When, for some reason make the output voltage exceeds 140 v, Q804 will rapidly conduction, the output voltage of short circuit, the voltage regulator circuit to stop working, and there is no output voltage. When breakdown because of his poor protection circuit of SCR itself will also short circuit output voltage, the switching power supply without losing, and with "make" scream. MZpservice manual download site
S1 (1) test is only 1.3 V output end, normal is 111 V, shut down over the ground resistance measurement S1 end approximately 1 Ω, shows that the 111 V output short circuit. MZpservice manual download site
(2) disconnect Q804 silicon controlled rectifier to carry over the ground resistance measurement S1 and about 500 Ω, normal, Q804 has wear, change Q804, TFD315M after work. MZpservice manual download site
(3) if measured to ground short circuit resistance is greater than 5.6 Ω S1 end, the fault may be good at output stage, focusing on Q551 line output pipe. MZpservice manual download site
Commissioning there will be no "squeak" sound. Replace Q804 should also check the voltage stabilizing circuit at the same time, MZpservice manual download site
Check whether there is any breakdown on Q8Q1.MZpservice manual download site