Electric pneumatic - valve trigger fault analysis

The trigger input, including the trigger on the oscillograph screen should have the pulse signal, to change the input signal polarity, the other side of the trigger pulse signal. Two groups of trigger pulse number and amplitude should be basically the same, otherwise has the following several ways no input signal ( Front magnetic amplifier under normal working state) A trigger pulse, the output end, may be the trigger pulse output side of the triode is damaged, or is c, e virtual welding; Resistance R204, R205, R208, R209 resistance change. No trigger pulse input signal, the output end, may be no unijunction transistor, the output pulse side damage; No one side of the output pulse pulse transformer primary or secondary circuit or short circuit. No one side of the output pulse diode ( D207 or D208) Short circuit. Output trigger abnormal has the following phenomena: no signal when the trigger pulse output, the two groups after add signal normal again, probably C202 electrolytic capacitor or C203 virtual welding; Start working on both sides of the trigger output is normal, after a period of time, the output pulse gradually disappear, may the knot tube has a problem; Positive and negative pulse output appear, may be a diode D207, D208 is punctured or virtual welding. After the inspection and maintenance, under the condition of control loop trouble-free servo amplifier should be able to work properly. Or has the following two cases: no input signal, the output voltage ( Voltage is close to 220 vac) May be SCR SCR1, SCR2 damage; Capacitance C301, C302 is punctured. When the input signal, no output signal or output voltage on the low side, could be in the diode D301 ~ D308 have been breakdown. SCR SCR1, SCR2 damage.