Turn P1 to maximum (maximum voltage of our power supply). Get your hands on a calibrated digital meter or a good analog meter and measure the voltage at the output of the power supply. P2 47 Ohm or 220 Ohm 1 watt * (be sure you can reach 0 ohms as any resistance limits the current) Part list for 6/8 Amp regulatable power supply (PSR28A68):ĭ1.D4 = four MR750 (MR7510) diodes (MR750 = 6 Ampere diode) or 2 x 4 1N5401 (1N5408) diodes.
Remember to use thick wires suitable for transfering the current needed according to the power supply you tend to build. If you do not isolated the finals from the heatsink, then please make sure the heatsink does not make contact with the chassis (metal casing where you plan to build the PS into). The collectors of the finals needs to be soldered with a wire all together if the transistors even if they are isolated from the heatsink or not. When using a 100 Ohm/1watt varistat the current is limited to approx. P2 will allow you to set the limit of the maximum available amps at the output +Vcc. The LM317 maximum output voltage is 30 volts, but using the diodes D7,D8 & D9 the output voltage is approx 30v - (3x 0.6v) = 28.2volt.Ĭalibrate your build-in voltmeter using P3 and, of course, a good digital voltmeter. To have a zero voltage on the output I've put 3 diodes D7,D8 and D9 on the output of the LM317 to the base of the 2N3055 transistors. P1 allows you to 'regulate' the output voltage to anything between 0 and 28 volts. Caution: 42 volt is the voltage that could be on the output if one of the transistors should blow. So all capacitors should be rated at 50 volts. The rectified voltage of: 30 volt x SQR2 = 30 x 1.41 = 42.30 volt measured on C1. Although the LM-317 power regulator will kick in on shortcircuit, overload and thermal overheating, the fuses in the primary section of the transformer and the fuse F2 at the output will secure your power supply.
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