Figure, VT1, VT2 and other components without steady-state self-excited multivibrator, the oscillation frequency of the C1, R2, R3, C2 and other decisions. The oscillator period is about 4 seconds. When VT2 output goes high, the VD plastic, VT3 conduction and light-emitting diodes by H1, current limiting resistor R6, triggering bidirectional thyristor VS. Now the normal conduction of thyristor VS, H2 LED light; when VT2 output is low, VD, VT3 deadline, VS deadline, H2 does not shine. H1, H2 synchronous flash to prove thyristor is good; if H1 and H2 is always flashing out, and said internal circuit VS; when the H2 Always, then the VS internal breakdown; when the H1, H2 is not flashing, indicating that VT1, VT2 circuit can not afford to vibration. This circuit also measures the diode, the diode when measured positive into the X1, the negative into the X2, H2 is tested tube light is good; back then plug, H2 should not be lit. This circuit can also measure the transistor. The base of the transistor into the X3, the emitter into the X2, the collector into the X1, if normal, the H1, H2 synchronous flash.
