The SMPS described here is suit-able for high-wattage stereos and other similar equipment. The circuit employs two high-voltage power transistors (BU208D) which have built-in re-verse-connected di-odes across their collectors and emitters. It can supply about 250-watt out-put. The circuit uses a ferrite core transformer of 14mm width, 20mm height, and 42mm length of E-E cores. An air gap of 0.5 mm is required between E-E junction. Good insulation using plastic-insulating sheets (Mylar) is to be maintained between each layer of winding.    Simple Switch Mode Power Supply Circuit Diagram   The number of primary turns required is 90 with 26 SWG wire. The secondary winding employs 17 SWG wire (for 4A load current). Each turn of the secondary develops approximately 2 volts. The reader can decide about the output volt-age and the corresponding secondary turns, which would work out to be half the desired secondary voltage. The volt-age rating of capacitors C7 and C...