Figure 2 Astable Multivibrator Driving Transformer/Rectifier. The transformer in this circuit could be a 120 volt to 24 volt center tapped turned around backward as described on the previous page. The plus twelve volt point goes to the anode of a silicon diode. The cathode goes to the center tap of the primary, low voltage side, of the transformer. The top of the primary winding goes to the collector of transistor QS1. The lower end of the primary goes to the collector of transistor QS2. The emitters of all 4 transistors are grounded. The base of QS1 connects directly to the collector of QM1. The base of QS2 connects directly to the collector of QM2. The collector of Qm1 goes through a capacitor, C, to the base of QM2. The collector of QM2 goes through another capacitor, C, to the base of QM1. Each base of QM1 and QM2 goes through its own resistor, R, to plus twelve volts. The high voltage secondary winding is not center tapped. Each side of the winding goes to the AC inputs, anode and cathode, of a bridge rectifier. The negative output of the bridge, two anodes, is grounded. The positive output, two cathodes, goes to the junction of a capacitor and filter choke. The other end of the capacitor is grounded. The other end of the filter choke goes to B plus point. The B plus point also goes to ground through another capacitor. The only problem with this circuit is that it won't work. I doubt if a combination of resistors R and capacitors C can be found that will make it work. This is a typical textbook circuit. At first glance it looks like it might work but it has never been tested. This completes the description of figure 2.
Go back.