2N3055 and LM317 power supply regulatable 0 28V 20 Amp

Part list for 20 Ampere regulatable power supply:

• 2 x 15 volt 20+- amps
• D1…D4= Bridge rectifier MB2504 (25 amps cooled)

  or eight BYW29 8 amp diodes (TO220 pinning cooled)
  or 8 x MR750 (MR7510) diodes (MR750 = 6 Ampere diode) or 16 x 1N5401 (1N5408) diodes.

• F1 = 2 Amp
• F2 = 25 amp
• R1 2k2 2,5 Watt
• R2 240 ohm
• R3,R4,R5,R6 0.1 ohm 10 watt
• R7 6k8
• R8 10k
• R9 47 Ohm 1 watt
• S2 mini switch
• R10 8k2
• C1,C7,C9 47nF
• C2 four times 4700uF/50v or one 22000uF/50v
• C3,C5 10uF/50v
• C4,C6,C9 100nF
• C8 330uF/50v
• C10 1uF/16v
• D5 1N4151
• D6 1N5401
• D10 MR750
• D11 LED
• D7, D8, D9 1N4001
• IC1 LM317
• Two 2N3055 transistors
• P1 5k
• P3 10k trimmer
• relay = 30 volts AC, 2×10 amp switching

S2 switches between +- 3 Amps and full output current

The relay is used to switch off the power supply voltage when the mains (S1) are/is switched off. So no delay do to the discharge of C2, and so preventing output voltages from not return to zero immediately.

A MB2504 is used as it is a 25 ampere rectifier bridge which also should be cooled. Or you could use eight BYW29 8 amp diodes (TO220 pinning) mounted on a heat sink.

Mount a little heatsink on the LM317 IC

Remember to isolate the 2N3055 transistors from the chassis/radiator! Use a radiator (heat sink) of appropriate size and surface area; insulating and heat-conducting spacer or at least a thin mica; hot adhesive and thermal paste.

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0 5 Watt power amplifier circuit with TDA1015T

This circuit is also Very simple and easy to make , simply by using the IC and 6 other components such as resistor and capacitor, you have to run this circuit. The IC uses TDA1015T , minimum voltage require 3 volt and maximum voltage required 12 volt. Power output 0,5 Watt mono , its low power amplifier.
Power amplifier Schematic below :

Click image to view larger

If the amplifier does not work , please check :

• Supply voltage
• Components , its damaged or not.
• Input connected or not
• Output connected or not
• Supply voltage of each components
• Line PCB.

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Simple 0 30 Volt Laboratory Power Supply

The linear power supply, shown in the schematic, provides 0-30 volts, at 1 amp, maximum, using a discrete transistor regulator with op-amp feedback to control the output voltage. The supply was constructed in 1975 and has a constant current mode that is used to recharge batteries. 

With reference to the schematic, lamp, LP2, is a power-on indicator. The other lamp (lower) lights when the unit reaches its preset current limit. R5, C2, and Q10 (TO-3 case) operate as a capacitor multiplier. The 36 volt zener across C2 limits the maximum supply voltage to the op-amps supply pins. D5, C4, C5, R15, and R16 provide a small amount of negative supply for the op-amps so that the op-amps can operate down to zero volts at the output pins (pins 6). 

A more modern design might eliminate these 4 components and use a CMOS rail-to-rail op-amp. Current limit is set by R3, D1, R4, R6, Q12, R10, and R13 providing a bias to U2 that partially turns off transistors Q9 and Q11 when the current limit is reached. R4 is a front panel potentiometer that sets the current limit, R22 is a front panel potentiometer that sets the output voltage (0-30 volts), and R11 is an internal trim-pot for calibration. The meter is a 1 milliamp meter with an internal resistance of 40 ohms. Switch S1 determines whether the meter reads 0-30 volts, or 0-1 amp. 

0-30 Volt Laboratory Power Supply Circuit diagram

 A more modern schema might use a single IC regulator, such as the MC78XX, or MC79XX series, immediately after the half wave rectifier, to replace approximately 30 components, or at least a high precision zener diode to replace D10 as the voltage reference. The LM4040 is one such voltage reference and has excellent stability over temperature. IC regulators such as the MC78XX series may eventually become obsolete as newer IC regulators are designed, however, discrete transistors, op-amps, and zeners are more generic, have a longer production lifespan, and allow the designer to demonstrate that he understands the principles of linear regulated power supply operation.Link

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