stabilised 10…350 volt power supply

• C9 5k 2x 125 mA slow blow FI S1 73 R17 DUS P2 R13 red DI4 DUG D15 R14 S4 oI • 100 mA 4V7 DUS 400mlell 68n DEI 2k7 RIO GI00 1800 ,I en—. R9 I: 0--0 o_. 4711 .311,--t5 300 V 100 mA There are probably many of our readers who possess high voltage valve power supplies which could do with some renovation and modernis- ation. With the wide choice of high voltage transistors available nowa- days it becomes a relatively simple matter to update such supplies. The BU 111 was used here, but the BU 126 or BUY 76 can also be used satisfactorily. Usually, the transformers used in this sort of supply have a number of high voltage tappings. In addition, there is nearly always a low voltage winding available. In this particular case a 300 V tapping was used for the high voltage side and a 9 V winding served to supply the stabilis- ation circuit. The latter is very simple and needs no explanation. About 420 V AC is produced once the 300 V tapping has been rectified (D1 ... D4). This is a rat...