Laboratory Type 0-50V 0-4A Adjustable power supply circuit The TL081 is a classic design based on the opamp .. I think I can remember the misconstrued diagram in the electrical or electronic circuit books ..
Laboratory Power Supply Transformer used in the power supply circuit with 4 BD249 transistors at the output stage. 50V AC output power can be used with a much stronger water rated at 4 amps. The only way out is to use 2X25VAC instead of 50VAC Transformer, which is actually better than this; Relay bypass circuit for regulated power supplies.
You can not use it because there are alternative ready-made modules in resistive jointed market to use voltmeter and ampermeter made with ICL7107 integration in regulated power supply circuitry and these materials are built-in. In the same PCB drawing of the same circuit, these elements have been added to make an additional 3.3k potency adjustment in the unused circuit.
Applicators of the laboratory type power supply circuit did not use an insulator for the power control transistors. In the design that can not have volt-amp meter elements, the T4 BD140 transistor is connected to the refrigerant but not necessary. Because the BD239 and BD249 transistors combine their collectors, there is no isolator in the coolant connection, so it contains all the coolant voltage. If you use a metal case for the power supply, you can break down if you come in contact with the chassis. Heat conduction and insulators.