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  1. audioguru2

    0-30V Stabilized Power Supply

    The voltage reference from U1 is 11.2V and the maximum output from the project is 30.0V. Then the output amplifier must have a gain of 30V/11.2V= 2.679 times. The power output transistors operate poorly at high frequencies. C6 and C9 make sure that their phase shift does not cause oscillation...
  2. audioguru2

    0-30V Stabilized Power Supply

    The LED lights to warn you that current regulation (constant current) is reducing the output voltage.
  3. audioguru2

    0-30V Stabilized Power Supply

    Where is the diode? The output stage has an opamp driving transistors configured as a darlington emitter-follower. The extremely high open-loop gain of the opamp causes this amplifier to be very accurate and have an extremely low output impedance. No. The small signal regulation is excellent.
  4. audioguru2

    0-30V Stabilized Power Supply

    The modified project has perfect stability, why change it? Then you have removed opamp U2 that provides very accurate voltage regulation when the load changes and have removed the adjustability of the output voltage and current.
  5. audioguru2

    0-30V Stabilized Power Supply

    Yes, but the math is simple: 1) The two 2N3055 output transistors have a minimum beta of 41 when the load current is 3A. 2) Then the maximum current of the BD139 driver transistor is 3A/41= 73mA. 3) The minimum beta of the BD139 at 73mA is about 50 so its maximum base current is 73mA/50=...
  6. audioguru2

    0-30V Stabilized Power Supply

    No. It draws only a little more current than its output current. With no load it draws about 20mA. With a 3A load it draws 3.3A maximum.
  7. audioguru2

    Complementary pair transistors

    You said "paired" but I think you mean "matched". Somebody must test and sort many transistors to make matched pairs. The test person must be paid a salary (or maybe a robot?). Matched transistors are expensive so they are rarely used. A circuit is designed with negative feedback that cancels...
  8. audioguru2

    0-30V Stabilized Power Supply

    78L05, can your power supply project produce 30VDC at 3A with low ripple? I think its maximum output voltage is about 25V or 26V at 3A. The little 2N2219 driver transistor and the single 2N3055 output transistor will be VERY hot when the output voltage is low and the current is 3A.
  9. audioguru2

    0-30V Stabilized Power Supply

    A 24VAC transformer produces 24VAC with its rated load. It might be 25V or 26V with no load. Your transformer is 26VAC (with or without a load?) but its peak voltage is 26V x 1.414= 36.8V and the rectifier bridge drops the positive unregulated supply to 35.4V or more. Your TL081 opamps are...
  10. audioguru2

    0-30V Stabilized Power Supply

  11. audioguru2

    0-30V Stabilized Power Supply

    The TL081 has an absolute maximum allowed total supply of only 36VDC. The original circuit used a 24VAC transformer (that is too low) that produced a positive unloaded supply of 32.5VDC or more plus a negative supply of -5.6V so the total supply for the TL081 opamps is 38VDC or more which might...
  12. audioguru2

    0-30 Vdc Stabilized Power Supply

    This is a linear power supply. The circuit for a switching power supply is completely different.
  13. audioguru2

    0-30V Stabilized Power Supply

    It sounds like you made the original circuit that has TL081 opamps and many errors. One error is the value of R10. The offset trimmer should adjust the lowest output voltage from about -50mV to +50mV. Without the trimmer the output opamp has an input offset voltage of maximum 15mV but the gain...
  14. audioguru2

    a site that post different components but functionally are almost identical

    Why don't you look at the datasheet to see that the maximum allowed voltage for a 1N4002 is only 100V peak but the maximum for a 1N4004 is 400V peak? The datasheet shows that the maximum allowed voltage for a 1N4007 is 1000V. Their maximum allowed current is the same. Use a 1N4005 or 1N4007 to...
  15. audioguru2

    led speaker design from I-Lit

    Buy a "Color Organ" kit that can be driven from the output of the mixer or from the output of the power amplifier. It drives LEDs of different colors with different frequencies. Some color organs can drive light bulbs.
  16. audioguru2

    0-30V Stabilized Power Supply

    You show two schematics with different parts designation numbers so it is confusing for me to say what is wrong. The transistor connected to the output of the voltage amplifier opamp is needed when the opamp is the original TL081 because it has the "opamp phase inversion problem" where its...
  17. audioguru2

    0-30V Stabilized Power Supply

    No. Q3 lights the LED to warn you that the current regulator is reducing the output voltage. It will light its LED even when the current regulator is set to 100mA and a load draws 110mA. It will also light when the output is shorted because then the output current will also be higher than the...
  18. audioguru2

    0-30V Stabilized Power Supply

    The BZX55C5V6 zener diode has a little better voltage regulation than the BZX79C5V6 zener diode. The reference voltage of about +11.2V should be stable and never change up and down. U2 and the driver and output transistors are a very simple amplifier with an adjusted voltage gain of...
  19. audioguru2

    0-30V Stabilized Power Supply

    R6 in your circuit is 1k. The voltage gain of IC3 is 2 so R6 has 5.6V across it then it sets the zener diode current at 5.6mA. My circuit uses a zener diode BZX79C5V6 rated at 5mA. There are a few other 5mA zener diodes available. Your older 1N752 zener diode is designed to be 5.6V at 20mA which...
  20. audioguru2

    0-30V Stabilized Power Supply

    I have never seen Circuit Wizard before so I do not know its errors. The part numbers on your schematic are different from the part numbers on the original and on my schematic: 1) You have IC3 as the 11.2V reference but I have U1. 2) You have D7 as a 20mA 5.6V zener diode but I have D8 as a 5mA...
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