200 watt amplifier power supply. There are a total of 6 transformers. The wide prong of the power plug goes to the bottom end of all 6 primaries. The narrow prong goes through the on/off switch then an 8 amp slow blow fuse to the top of the primaries of 4 of the transformers. All of these are rated at 28 volt 8 amps. The end of the 8 amp fuse away from the switch goes to a 1/2 amp fuse then to the top of the primary of a 12 volt 300 mA transformer. Another 1/2 amp fuse and 12 v 300 mA transformer are similarly connected. The 28 v 8 A secondaries are connected in series in pares. Each pare goes to its own bridge rectifier. These bridges are made up of 200 v 15 amp stud diodes mounted on a heatsink. The negative of the top bridge goes to common while the positive of the bottom bridge goes to common. The positive output of the top bridge goes to the positive of a 9800 mike 100 v cap, the other end goes to common. The negative output of the bottom bridge goes to the negative of another 9800 mike 100 v cap and the positive end goes to common. The common point where the bridges and capacitor leads come together is where the speaker returns are connected. The two cathodes of the upper bridge go to the plus 71 v output. The anodes of the lower bridge go to the minus 71 v output. The point where the two upper 28 v secondaries connect together is brought out to the anode of a 1N4003 diode. The cathode goes to the plus side of a 1000 mike 50 v cap, the negative side goes to common. The plus of the cap goes to the input of an LM317 adjustable positive voltage regulator I C. The input and output terminals of the I C are bypassed to the A terminal by two 0.1 mike caps. These caps are physically close to the I C. The A terminal goes to common through a 10 mike 25 v cap. The output terminal goes through a 120 ohm res then a 5 k ohm pot connected as a rheostat to common. The junction of the resistor and rheostat connect to the A terminal. There is a 22 mike 50 v cap from the output to common. The output is the plus 25 v output of the power supply. The point where the two lower 28 v secondaries connect together is brought out to the cathode of a 1N4003 diode. This circuit is an exact mirror image of the one above. It uses an LM337 negative regulator I C and supplies the minus 25 volt buss. At the top of the circuit one of the 12 v 300 mA transformers has its secondary connected to a bridge rectifier made up of 1N4002 diodes. The negative bridge terminal goes to plus 71 volts. The positive output of the bridge goes to the plus side of a 1000 mike 25 v cap, the negative side goes to plus 71 v. The plus side of the cap goes to the input terminal of an LM7812 fixed positive voltage regulator. The input and output are bypassed to the common by two 0.1 mike caps. The I C common goes to plus 71 v. A 100 mike 25 v cap is connected from the output to plus 71 volts. A diode marked as 5 amps has its cathode connected to the I C output and the anode goes to plus 71 volts. The output goes to the plus 83 volt buss. At the bottom of the supply the other 12 v 300 mA transformer is connected in a mirror image circuit using an LM7912 fixed negative voltage regulator I C. All diodes and capacitors are reversed. It connects to the minus 71 volt buss and its output is the minus 83 volt buss. End verbal description.
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