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  1. audioguru2

    0-30 Vdc Stabilized Power Supply

    We already discussed a 5A power supply. Two output transistors will get too hot when the current is 5A and the output voltage is low or shorted so 3 output transistors are used, each with a 0.33 ohm emitter resistor and a very large heatsink. The single BD139 driver transistor will be fine but...
  2. audioguru2

    Function Generator Simulation (Need Help)

    I found the original project here: http://sound.westhost.com/project86.htm Your schematic is missing a wire that reduces distortion called "feedback" on the text.
  3. audioguru2

    Function Generator Simulation (Need Help)

    The original circuit uses both opamps in each TL062 dual opamp. But your circuit uses only one opamp in each TL062 dual opamp. One TL064 quad opamp could also be used. The original circuit is powered from the 9V battery at the right side of the schematic. But your circuit has the 9V battery and...
  4. audioguru2

    Function Generator Simulation (Need Help)

    Your circuit does not work because you show power supply V3 as a positive voltage but it is supposed to be a negative voltage. Your PNG schematic is covered with the same kind of fuzz that covers a JPG file type schematic.
  5. audioguru2

    Function Generator Simulation (Need Help)

    Please post your schematic as a normal PNG file type so we can all see it.
  6. audioguru2

    0-30 Vdc Stabilized Power Supply

    If you are making the 3A power supply that uses a 0.47 ohm current sensing resistor then 1A gives a voltage across it of 0.47V and 3A gives a voltage of 1.41V. The 200mV voltmeter you use to show current needs a voltage divider to reduce the 1.41V to 30mV. The voltmeter probably needs a power...
  7. audioguru2

    0-30 Vdc Stabilized Power Supply

    The voltage across the current sensing resistor is compared by opamp U3 to the voltage set by the current setting pot.  The voltage is much higher than 200mV so a voltage divider is needed to reduce it. When the voltage divider is calibrated then a load of 3A will read 3.0A. A load of "2A" will...
  8. audioguru2

    0-30V Stabilized Power Supply

    If you want an output of 10A then of course you need a transformer with more current, a bridge rectifier with a higher current rating and a bigger main filter capacitor. What will drive 6 output transistors? The single little BD139 driver transistor cannot. Replacing the driver transistor with...
  9. audioguru2

    0-30V Stabilized Power Supply

    A 2N3055 transistor has a maximum allowed collector current of 15A but works poorly at 10A and more because at 10A its minimum current gain is only 5 and it has a maximum saturation voltage loss of 3V when its base current is a whopping 3.3A. If you can keep its case at 25 degrees C somehow...
  10. audioguru2

    0-30 Vdc Stabilized Power Supply

    29.7VAC  has a peak of 42.0V. With a full load the recifier bridge will drop 2.0V and the filter capacitor will have maybe 2V of ripple. The output opamp has a saturation loss of 1.8V, the driver transistor has a voltage loss of 1.0V, the output transistors have a voltage loss of 1.5V and the...
  11. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Josko, Picmaster's schematic does not list its transformer voltage. It should be 28VAC or 30VAC. The circuit should regulate the output well up to 30VDC at the output, not 38V. Opamp U3 regulates the output current by comparing the voltage set by the current-setting pot to the voltage caused...
  12. audioguru2

    0-30 Vdc Stabilized Power Supply

    I don't know why you want to reduce the output voltage when the circuit is turned off. C1 holds a large charge to reduce ripple in the output. Maybe a second contact on the on-off switch can discharge it quickly through a low value resistor. 
  13. audioguru2

    0-30 Vdc Stabilized Power Supply

    C1 already has a bleeder resistor, R1. It is 2200 ohms so it will take about 3.7 minutes to discharge your capacitor but the electronics will also discharge it so maybe in 1 minute.
  14. audioguru2

    0-30 Vdc Stabilized Power Supply

    R7 connects between the power supply 0V and the output 0V. The output 0V becomes a positive current-sense voltage when there is load current.
  15. audioguru2

    0-30 Vdc Stabilized Power Supply

    The meter is a voltmeter so it does not have mA ranges. If it is set for the 200mV range then it will read 200mV which is too low when a current of (200mV/0.27 ohms)= 0.74A. when the current is 5A then it will try to read over-range at (5A x 0.27 ohms)= 1350mV. If it is set to 20V range then...
  16. audioguru2

    0-30V Stabilized Power Supply

    Thank-you, Tompa. Your zipped file unzips perfectly. I don't have time to look at it all.
  17. audioguru2

    0-30V Stabilized Power Supply

    Thanks Tompa. I downloaded your RAR file and tried to extract its files with Windows XP and I got 116 errors. The RAR file is 10.5MB. It extracted one folder named PSU. Inside the PSU folder is more folders: Audio (empty) PICmaster_str50 (empty) tesseract_str27 (empty) EL-PS6_redwire  Inside is...
  18. audioguru2

    0-30 Vdc Stabilized Power Supply

    Sparkington, You forgot to connect the driver and output transistors to the power supply (the input of the 7809 regulator). Ivan used the original circuit and most of its parts then added a 7809 regulator and an 18V zener diode so that the maximum unregulated supply voltage to the opamps is...
  19. audioguru2

    0-30V Stabilized Power Supply

    I did not save any pcb designs because I don't know if they work properly and I don't use Eagle pcb software. I never made this projec, instead I discuss corrections and improvements to it..
  20. audioguru2

    0-30V Stabilized Power Supply

    There are at least two latest pcb's. One (Picmaster's?) changed all the parts designation numbers so it is difficult to talk about. One or both of them moved around some of the parts so their schematics are different from mine.
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