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  1. audioguru2

    0-30V Stabilized Power Supply

    Which version? Which opamps? Opamp U3 us used as a comparator with a voltage gain of about 200,000. Its output switches on and off, not as a linerar fader. It turns Q3 off when the output current is less than the setting of the current-setting pot. If there is a load then the voltage setting pot...
  2. audioguru2

    0-30V Stabilized Power Supply

    You are trying to make the original circuit that does not work properly and has many overloaded parts. We fixed it and changed it and the new schematic and new parts list have been posted here many times. Your 25VAC transformer produces a positive unregulated voltage of only 34VDC which is too...
  3. audioguru2

    0-30V Stabilized Power Supply

    I do not know what you are asking. Many transformers have 4 windings so they can be used with 115VAC or 230VAC and can be 15V at high current or 30V at lower current.
  4. audioguru2

    New to electronics

    BCxxx and BDxxx transistors are European. I live in North America so I buy 2Nxxxx transistors. Datasheets are available from many online sites but I get mine from wwww.datasheetarchive.com where I can select which manufacturer. NTE simply buy transistors, add their part number and increase the...
  5. audioguru2

    Replacement for 2SK533

    You don't have and I couldn't find a proper detailed datasheet. We don't even know if it is an N-channel or P-channel Jfet. Since its IDSS (typical?) is listed as 9mA then try a 2N5459.
  6. audioguru2

    0-30V Stabilized Power Supply

    The peak voltage from the transformer is 39.6V from a 28V transformer and is 42.4V for a 30V transformer. So 39.6V x 10A= 396VA and 42.4V x 10A= 424VA. The windings must be completely separate if you are making a +/- power supply or if you are adding them to get up to 60VDC. You cannot connect...
  7. audioguru2

    Solid state...transistor amp design problems

    In addition to not knowing how to simply correctly bias a transistor, you don't know how to simply calculate vales for capacitors. Your input capacitor is so small that it does not pass audio frequencies. I commented on the capacitor values for my mic preamp. I didn't use Spice to make my...
  8. audioguru2

    0-30V Stabilized Power Supply

    Hi Fikic, On your pcb layout you have a few tracks too close together. Many traces under the ICs do not carry much current so they do not need to be as wide as you made them.
  9. audioguru2

    Solid state...transistor amp design problems

    Yes, if the capacitors have correct values, have the correct polarity and the amplifier has an input impedance of  47k or more. The voltages show that the mic preamp will work well. Yes. It is at the top of each of your recent posts (before you press REPLY beside DELETE and another button. Use...
  10. audioguru2

    Solid state...transistor amp design problems

    What is the input source? A dynamic microphone? A dynamic microphone has a coil and a magnet. This preamp will not work from a common electret microphone unless the microphone is powered from a 10k resistor connected to the filtered positive supply. The input impedance is too low to be driven...
  11. audioguru2

    Solid state...transistor amp design problems

    I still have some old BC109 transistors from when I worked at Philips 44 years ago. It is replaced by the BC549 which is also low noise. Now there is another forum with this simple guitar preamp circuit. On the other forum somebody thought it is a power amplifier to drive a speaker! The person...
  12. audioguru2

    0-30V Stabilized Power Supply

    Yes, there must be space for the 3rd output transistor. I can't remember where the emitter resistor is located.
  13. audioguru2

    0-30V Stabilized Power Supply

    The transformer must supply 28VAC at 200VA or 30VAC at 212VA. There must be three output transistors with emitter resistors and a pretty big heatsink. The heatsink for the driver transistor Q2 must be a little bigger. The current sensing resistor R7 must be 0.27 ohms/10W.
  14. audioguru2

    Solid state...transistor amp design problems

    You need to learn about how to bias a simple transistor. You still have the transistors saturated (the collector voltage is as low as it can go) so they are not an amplifier. I corrected the biasing so that the collectors of the transistors can swing up and down and swapped the two transistors...
  15. audioguru2

    0-30V Stabilized Power Supply

    Then the output voltage at 3A will be only about 25VDC instead of 30VDC and when you turn the voltage-adjust knob higher then the output will not be regulated and will have lots of ripple. You won't notice any difference. Big electrolytic capacitors have a very wide tolerance. The 10,000uF one...
  16. audioguru2

    0-30V Stabilized Power Supply

    U1 has nothing to do with any transistors. It is an 11.2V reference that is fed power through a 10V zener diode so its power supply is only 30V. U2 operates with a +41.7V total supply. Its max allowed supply is 44V. Opamps smoke and crack if their power supply voltage is connected backwards...
  17. audioguru2

    0-30V Stabilized Power Supply

    Hi Waste, The revised power supply uses two output transistors. The TIP3055 in the plastic TO-220 case is not allowed to get as hot as the metal TO-3 case. Therefore a very big heatsink will be needed. Here (again and again) are the latest schematic and parts list:
  18. audioguru2

    0-30V Stabilized Power Supply

    Waste, you don't say which country you are in. I usually go to Digikey and buy opamps.  MC34071 opamps cost only $1.02US each and TLE2141 opamps cost only $1.71US each today. For comparason, the original circuit's TL081 opamps cost $.52US. So the cost for only 3 of them is almost nothing. But...
  19. audioguru2

    0-30V Stabilized Power Supply

    Ivan's circuit has a max output voltage of only about 20V and the transformer and many other parts still overheat and will fail.
  20. audioguru2

    0-30V Stabilized Power Supply

    Then the max output voltage will be only 8V to 10V and the overloaded transformer and many other parts will still overheat.
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