According to the phenomena considered ZK connection is bad, or the digital section switch has a set of electronic switching of the relay burned out. Disconnect the input air switch, check the wall control switch on ZK, and off is normal, that fault lies in the digital section switch. Remove the digital section switch, open the enclosure has no odor, intuitive and there is no trace of damage, thus temporarily connect a power cord. Power survey. When you order when switching the mains, ICHEF4017BP ② ③, ④ feet each of which has voltage output, measuring about 0.7V Ql, Q2 's emitter junction voltage, that Ql and 02 to the corresponding work in conducting State and normal. When IC voltage of ② ④ feet respectively when the output relays can be heard very slight trembling sound within. Two relay coil voltage is measured only about 6.5V, and when the Ic and aim at the feet when there is a voltage output, does not even trembling voice. Relay coil voltage is lower (around 3.6V or so), this is not normal. The voltage value is too far from the relay 12V of the nominal value, does not work. Based on this testing, smacks of rule out relay contact is burnt out. Strong power supply part is faulty.


After the examination, the rectifier and filter part of the VDl, VD2, 1D1, D2 is normal, measuring capacitor C2 ends when the power voltage is only about 6.5V, suspected C2, C3 or C4 of leakage, remove the three capacitance measurements were normal. So doubt step-down current limiting capacitor Cl (1uF) failures, weld removal C1, whose capacity is O.231xF, has expired. After replacing power. Relay with a crisp snap sound, C2 voltage measured at approximately 9.65V (main 228VB), after using the device back to normal.

From C2 to the actual voltage at both ends (9.65V), when the machine is working properly, the voltage is not enough to make Zener diodes (voltage value to 11V) Breakdown voltage. Design actually keep the cushion to mains pressure only when the breakdown voltage. So as to protect the stability of the circuit.