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  1. audioguru2

    0-30V Stabilized Power Supply

    One minute ago I answered your PM. Tell us the voltage measurement of C1, the output voltage of U1 and the -5.6V voltage and we will fix your power supply circuit. Does the LED light up?
  2. audioguru2

    0-30V Stabilized Power Supply

    With an output current of 5A and even if the main filter capacitor is huge the positive unregulated supply will have plenty of ripple that might be coupled to the 11.2V reference voltage or to the output amplifier. Careful wiring layout will avoid coupling and the addition of a constant current...
  3. audioguru2

    Power Supply 0-30V

    The project has been made with a max output current of 5A by using a suitable high current transformer and three output transistors that dissipate a max power of 71W each.
  4. audioguru2

    Power Supply 0-30V

    You want 3.3 times the output current. Then when the output current is set to 10A and the output voltage is very low (shorted?) the power dissipation in the output transistors is 424W and they will melt.
  5. audioguru2

    0-30V Stabilized Power Supply

    The original cheap kit had many overloaded parts. Its max voltage at 3A was only about 25V (not its rated 30V) and had too much ripple. There are many projects with many errors. Some people made the original versions so they are still here. The latest parts list has been posted many times.
  6. audioguru2

    0-30V Stabilized Power Supply

    The project draws a max of 127VA. Therefore its max current from 115V is about 1.1A. Use a slow-blow 1.5A fuse. A fast-blow fuse will blow trying to charge the huge filter capacitor.
  7. audioguru2

    Line-input splitter w/isolation transformers

    Some sound products can drive an isolation transformer as low as 600 ohms. 51 ohms is like a dead short to them. Are you talking about a 600 ohm impedance to 600 ohm impedance transformer that has a DC winding resistance of 51 ohms to 70 ohms? A mixer with a low output impedance can drive...
  8. audioguru2

    4W FM transmitter

    We have two Greek 4W FM transmitter projects. The Smart Kit one linked by Alex is the other one that also does not have pre-emphasis: http://www.electronics-lab.com/projects/rf/001/index.html
  9. audioguru2

    0-30V Stabilized Power Supply

    If the transformer is 28VAC then its peak voltage is 39.6V. When the output of the project is 5A then the transformer must supply 39.6V x 5A= 198VA continuously. Then the 28vAC transformer must have a current rating of 198VA/28V=  7.07A. A 30V transformer must be rated at 212VA and also must...
  10. audioguru2

    0-30V Stabilized Power Supply

    An LM317 with only one type of  power transistor does not limit the current. A PNP transistor can be added to limit the current. A current-limiter is not an adjustable current regulator.
  11. audioguru2

    0-30V Stabilized Power Supply

    The original version is still there so we can laugh at it. I agree that the latest version should be added.
  12. audioguru2

    0-30V Stabilized Power Supply

    Can you sneak across the border into the USA?? Its inputs don't work when they are closer than 4V from the negative supply pin.
  13. audioguru2

    0-30V Stabilized Power Supply

    The MC33171 is low power so its bandwidth is too low for this circuit. The MC34002 has a max supply of only 36V which is too low and its inputs do not work anywhere near ground. Digikey in Canada and the USA has 439 MC33071, 1323 MC34071 and hundreds of TLE2141 opamps in stock today. Newark in...
  14. audioguru2

    0-30V Stabilized Power Supply

    The original circuit had many parts overloaded. For example its current was not calibrated so when set to max it was typically 4.1A (it could be higher if you have parts on the wrong side of their tolerance). So the poor little 0.47 ohm/5W resistor was dissipating 7.9W and was almost...
  15. audioguru2

    0-30V Stabilized Power Supply

    Then throw them away and use good diodes that are very inexpensive.
  16. audioguru2

    0-30V Stabilized Power Supply

    The original circuit with 0.47 ohms had a max current of about 4.1A which is too much for most of the parts. With 0.54 ohms the max current before calibrating will be about 3.5A before calibrating.
  17. audioguru2

    0-30V Stabilized Power Supply

    D7 is a 5.6V zener diode. Its voltage should be -5.6V so maybe you installed it backwards and maybe D5 and D6 are installed backwards. U2 will not work properly without a -5.6V supply. The output from U2 should go from about +1V to about +32V in your circuit. It is low because your 24VAC...
  18. audioguru2

    0-30V Stabilized Power Supply

    To get a 30A output then the output transistors must dissipate a total of 1,188W at times. Liquid nitrogen will be needed to cool them. The driver transistors also must be many. Opamp U2cannot drive many driver transistors so a pre-driver transistor or a few of them and a pre-pre-driver...
  19. audioguru2

    0-30V Stabilized Power Supply

    Check that the -5.6V supply is actually -5.6V. U3 is the current regulator that detects the voltage across R7 that is caused by load current and compares it to the voltage of the current-setting pot which goes from almost 0V to +1.92V. Since the (+) input of U3 connects to the current setting...
  20. audioguru2

    0-30V Stabilized Power Supply

    It is a very simple circuit. Tell us which version you made and the problem you have with it and we will tell you the voltages that should be measured and what might cause your problem. For example the output of U1 is always 11.2V. The output of U2 is about 1.7V higher than the output voltage.
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